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TPS or other problem - drives erratic


mytc05
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     Hi all,

     One of my TC's is driving erratic. It has pretty much since I got it a few months ago and started driving it. It's throwing the check engine light now as well with codes:

12, 24, 21 and then the ending code 55. We had already replaced the Throttle Position Sensor with an aftermarket, and it kept acting up and throwing the code. So, I pulled the one of my parts car to see if that worked better. Same problems and still getting the code. When idling, it constantly accelerates and decelerates the throttle between 400 RPM to about 1,100 RPM. If I put it in neutral when I sit at a light and it's doing this, a lot of the time, it then revs up to about 1,100-1,600 RPM and holds it there. Also, sometimes when I step on the gas, it hesitates for a few seconds before it responds, unless I really step on it. It's also occasionally dying on me at lower speeds. Anyone have any suggestions. When it's not acting up lie this (which is rare, but does ocassionally happen), it runs great! Would something else besides the TPS throw a TPS error and cause these issues? It's been really frustrating, and just can't figure out what is causing this. Any help would be appreciated!

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Have you cleared the codes since you ran the test?   Do so.  Then run the engine again and check the codes. 
12&55 mean nothing in the test.

24 - Throttle position circuit 

21 - Oxygen sensor circuit 

 

I would personally suspect the MAP Sensor Circuit, which includes all vacuum hoses leading to that sensor.  Even though you have no codes present for that.

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@Hemi Dude and @avgwarhawk Thanks for your insight guys. The MAP Sensor has been replaced previously. Hemi, I did clear the codes back in July, and it's continued to throw 24 again after. The 21 oxygen sensor fault has just come up recently. We did replace a vacuum hose line that was affecting the HVAC not blowing through the panel when on high fan speeds. It was good for a while, but now that has acted up again and never blows out the panels anymore. The 24 code and erratic behavior has continued since before and throughout these changes though. I'll have to take a look at the vacuum lines along the circuit and see if maybe there's another leak somewhere. The TPS and the MAP sensor were the two main things we could think of, but I'll be damned that neither has made any difference with this. Like I said, once in a while it runs great for a drive, but it is short lived, and then goes back to this. Erratic throttling, sometimes erratic shifting, and occasionally dying at low RPM. It's so frustrating because it's been a little gremlin issue since I got this second TC. I appreciate it guys!

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15 hours ago, mytc05 said:

@Hemi Dude and @avgwarhawk Thanks for your insight guys. The MAP Sensor has been replaced previously. Hemi, I did clear the codes back in July, and it's continued to throw 24 again after. The 21 oxygen sensor fault has just come up recently. We did replace a vacuum hose line that was affecting the HVAC not blowing through the panel when on high fan speeds. It was good for a while, but now that has acted up again and never blows out the panels anymore. The 24 code and erratic behavior has continued since before and throughout these changes though. I'll have to take a look at the vacuum lines along the circuit and see if maybe there's another leak somewhere. The TPS and the MAP sensor were the two main things we could think of, but I'll be damned that neither has made any difference with this. Like I said, once in a while it runs great for a drive, but it is short lived, and then goes back to this. Erratic throttling, sometimes erratic shifting, and occasionally dying at low RPM. It's so frustrating because it's been a little gremlin issue since I got this second TC. I appreciate it guys!

OK now. What component outside the MAP sensor and the TPS could be involved in engine speed increase, without throttle plate opening, at IDLE SPEED? 

The AIS motor which is actually the physical / mechanical part capable of altering Idle Air volume. The AIS is driven through and by the SMEC as we in MOPAR call it.  SOMETHING has to be sending varying signals to the AIS unless there is a physical problem with the AIS itself. Has anyone removed it for cleaning? Also, has anyone cleaned the throat of the throttle body around the throttle plate?  

Another area to investigate is the distributor itself. Check the ‘SHUTTER BLADES’ to verify that they are firmly attached to the distributor drive shaft itself. Any looseness here can affect the primary signals from the HALL-PLATE PICK-UP. 

These are merely other areas to check while searching for your erratic idle speed problem.

At the age of these cars and having multiple owners over the years, it is hard to imagine that there have not been many hands in this engine compartment many many times and from a distance, diagnosing with eyes closed comes down to this, “looking at the most obvious” possibilities. I have seen many turbo engines that have had the vacuum lines repaired or replaced over the years AND hardly any people are aware of the vacuum restrictors in the original lines that get thrown away and new fully open vacuum lines installed.

image.jpg.35ad9defab4238f6e0f496a80239d34a.jpg

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On 8/30/2022 at 2:07 PM, mytc05 said:

We had already replaced the Throttle Position Sensor with an aftermarket, and it kept acting up and throwing the code.

Does the TPS on these engines need to be adjusted after replacement or are they nonadjustable?

 

On 8/30/2022 at 2:07 PM, mytc05 said:

... Also, sometimes when I step on the gas, it hesitates for a few seconds before it responds, unless I really step on it. It's also occasionally dying on me at lower speeds. Anyone have any suggestions. When it's not acting up lie this (which is rare, but does ocassionally happen), it runs great!

Have you checked the fuel pressure? That's exactly the symptoms I was having when my fuel pump was going bad on my Buick 3800. The first thing I noticed was a hesitation when pulling away from a red light and sometimes the idle would fluctuate but not as much as yours is. Then it started getting hard to start. A fuel pressure tester showed the pressure was down to 32 psi. The spec is about 38-42. After more testing, checking the pressure regulator and and changing the fuel filter, I knew the pump was bad. Replacing the pump fixed the problem. You can read about it here if you like.

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37 minutes ago, Hemi Dude said:

What many of the TC owners need are resources for the Teves ABS brake system parts, interchangeable with the Reatta and other GM vehicles using this system.

We Reatta owners try to keep the Teves system going for as long as we can but at some point we will all, Reattas, TCs, etc., will probably have to go to a vacuum assist system like you did. Parts for the Teves are getting harder and harder to find.

 

There are several people on the Reatta Owners Journal forum that are very knowledgeable on the Teves system as far as working on them and finding parts. If any TC owners have any question about the Teves system they are welcome to post them on ROJ and we will be glad to help if we can.

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Hey @Hemi Dude, @avgwarhawk and @Ronnie, Just wanted to say thank you for this input! I finally got a chance to go through some of this with my dad tonight. He's the mechanic, and I have to either have him do the work when I visit home, or I have to have him walk me through it over the phone. Finally got a chance for us to discuss this tonight, and take a look. So, a few things. We had repaired the vacuum line from the HVAC panel to the throttle body area, about a month ago when he was passing through town very briefly, as that line was broke. Tried to make due with a larger diameter hose and some tape, as I didn't have the right hose, and we didn't have time to run to an Autoparts store. Well, that line had fallen off, which was why my A/C wouldn't go back to panel at all. I knew something was up, but had to wait for him to walk me through it over FaceTime tonight. We had also replaced the check valve on that line about two months ago, but the aftermarket seems like it's junk and doesn't provide as good of a seal as it should. So, thinking I should replace that with a Chrysler part instead. So, I went to the auto parts store tonight and got some windshield washer fluid line and put it on the vacuum control valve and slid the OEM vacuum line that was coming out of the firewall inside the other end of the new line. Seems to be a tight fit. So, hoping that fixes that for good.

 

As I mentioned, we had replaced the TPS with an aftermarket, but it was still acting up. So, I pulled the TPS off of a parts car that I have to see if that OEM one would be better, and it's still continued to give problems. My dad had mentioned cleaning the IAC previously, which I hadn't done yet. So, with y'all also suggesting that, I took it off tonight. Doesn't look particularly gummy in there to me, but I'm by no means an expert. I think I'm going to pull my IAC off the parts car as well, and clean that with some carburetor cleaner and put that one on to see if it resolves the problem. Didn't see any other easily noticeable vacuum line issues, such as tears or broken lines. When I first got this car, it was running horrible, and wouldn't stay running. The previous owner had already replaced the fuel filter and the MAP sensor. So, we swapped the SMEC from my parts car, and that helped a ton. So, hoping that SMEC is not the issue, as it seemed fine for the first little bit.

 

Going to do thta IAC cleaning and swap in the next day or so, and that, along with the new vacuum line replacement, I'm hoping will resolve it. Fingers crossed. More recently, when I step on the gas after sitting at a light, it hesitates for a second or two before it really starts to grab and go. Stepping down further on the gas seems to help. Not sure if that is part of this issue as well or what, but that's a somewhat more recent development. Also, recently, I've been having a problem sometimes with the cruise set around 50 where it pulses roughly, almost as if it's trying to hard accelerate and then let of hard back and forth. That started more recently as well. So, this all might be connected. Just figured I'd mention in case that points to anything more particularly. What's so damn frustrating is, when it doesn't act up, it runs great! Sometimes, even sitting at lights or pulling away from them, (like it did tonight on the way to the parts store), it ran great. Nice and smooth. So, it's strange. Thanks again for the insight thus far gentleman. I'll let you know what happens after the IAC cleaning and swap.

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My 2cents worth--when I tried to clean the IAC of my car with carburetor cleaner, it somehow dissolved the inner workings, resulting in my having to replace it with a new unit.. Replacing it with an OEM unit cleared up my problem completely. 

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It is the air passage in the aluminum throttle body that you want to clean and the area around the surface that the throttle plate closes that you want to clean with the carburetor cleaner and ONLY the tip of the pintle of the IAC, as we commonly call it now. 

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21 hours ago, Hemi Dude said:

It is the air passage in the aluminum throttle body that you want to clean and the area around the surface that the throttle plate closes that you want to clean with the carburetor cleaner and ONLY the tip of the pintle of the IAC, as we commonly call it now. 

Thanks guys. I pulled the IAC out last night, and it looks clean to me. I didn't notice anything gumming up the metal tip or the spring. It seems it can be screwed in tighter or looser. Is that something that has to be calibrated properly for it to work correctly? I'm not sure how tight it should be screwed down on the spring.

Edited by mytc05 (see edit history)
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19 minutes ago, mytc05 said:

Thanks guys. I pulled the IAC out last night, and it looks clean to me. I didn't notice anything gumming up the metal tip or the spring. It seems it can be screwed in tighter or looser. Is that something that has to be calibrated properly for it to work correctly? I'm not sure how tight it should be screwed down on the spring.

You should NOT screw with it at all! The motor drives it in and out to control the idle speed.  Screw with it and YOU are SCREWED!

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Word to the wise ::: I have found that New, OEM parts, even though they may cost more, save you a fortune in headaches

 

Can't tell you the number of times that old, or new 'low-cost" parts have caused me frustration when troubleshooting.

 

Even though the old part may have been working-How well was it working??

 

I'd replace it to be sure...

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Hey @Hemi Dude, when I removed it, as I was setting it down, it came apart. The pintle, spring and black ring came down as the pintle seemed to have barely ben screwed on. I was easily able to screw it right back on. It seems like it should be fine. Are you saying something is wrong if it came off and easily screwed back on? My original question was how much to screw it back down, but not sure if you're saying it's junk?

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9 minutes ago, mytc05 said:

Hey @Hemi Dude, when I removed it, as I was setting it down, it came apart. The pintle, spring and black ring came down as the pintle seemed to have barely ben screwed on. I was easily able to screw it right back on. It seems like it should be fine. Are you saying something is wrong if it came off and easily screwed back on? My original question was how much to screw it back down, but not sure if you're saying it's junk?

There is a strong possibility that the loose pintle is the cause of your problem. In the field, we never mess with the individual parts of the IAC  I would suggest screwing it in about half way, by going as far as you can without forcing anything, then screw it out 1/2 the number of turns you made screwing it in. Stick it back into the throttle body, plug it in and start the engine. Be ready to shut the engine off if it revs too high on startup, BUT if within normal RPM range, allow the SMEC to regulate the IAC to the desired idle speed which will be a little high but should come down to around 700 RPM after a short time.

Keep us informed.

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Hey guys, any chance you know the OEM part number for the IAC for a 1990? Called a dealer to get a quote, and they said they have no parts for the car at all. *eye roll*. The age and the Maserati name always scare the parts guys. I see 136 on the end of the part, but the rest is worn off. From googling, it looks like this one might be aftermarket. Don't have a parts guide any more for these. So, wanted to check.

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Actually, I think I found it. #04861084. From calling a dealer with this part number, it looks like Chrysler doesn't stock this part anymore. So, OEM from a dealer is out. Looks like moparpartsgiant.com has it, but never ordered from the before. Not sure if they're legitimate. In looking back at some paperwork a bit, and looking at this part, the previous owner did in fact replace it not long before I got the car. So, it makes me think it's maybe not an IAC issue. Not sure what else would be causing it. I have a short video of what it's doing a lot at idle, but I can't share video files on the forum. It basically pulses at stop lights pretty bad, and sitting still starts to die (or sometimes does die) when it drops below 400 RPM, and then it over revs up to say 900 RPM and then goes back down. As I mentioned, sometimes when I step on the gas pulling away from idle, it hesitates for a few seconds before it really starts to respond. If I drop it into neutral while siting at a light, it often revs up to around 1500-1700 RPM and often will just sit there. Ugh.

 

By the way, @Hemi Dude, I did try your recommendation on srewing it half way in and then reversing part way and re-installing. Same problem still, even after taking it for a drive. This one's got me stumped.

Edited by mytc05 (see edit history)
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29 minutes ago, mytc05 said:

Actually, I think I found it. #04861084. From calling a dealer with this part number, it looks like Chrysler doesn't stock this part anymore. So, OEM from a dealer is out. Looks like moparpartsgiant.com has it, but never ordered from the before. Not sure if they're legitimate. In looking back at some paperwork a bit, and looking at this part, the previous owner did in fact replace it not long before I got the car. So, it makes me think it's maybe not an IAC issue. Not sure what else would be causing it. I have a short video of what it's doing a lot at idle, but I can't share video files on the forum. It basically pulses at stop lights pretty bad, and sitting still starts to die (or sometimes does die) when it drops below 400 RPM, and then it over revs up to say 900 RPM and then goes back down. As I mentioned, sometimes when I step on the gas pulling away from idle, it hesitates for a few seconds before it really starts to respond. If I drop it into neutral while siting at a light, it often revs up to around 1500-1700 RPM and often will just sit there. Ugh.

 

By the way, @Hemi Dude, I did try your recommendation on srewing it half way in and then reversing part way and re-installing. Same problem still, even after taking it for a drive. This one's got me stumped.

It appears that they have this part number, they look legit, the question is; Does this part plug into your harness?  And will it operate properly on your car. If you speak with someone there, ask what year, model and engine this 4861084 part was originally for. That should give us some idea as to it's ability to function on your TC.

The 2 AIS (IAC) motors for the 89 four cylinder engines, 8V & 16V,  are discontinued and NS1, No Longer Available according to them.

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Check Rock auto  they list three for the TC, by AC Delco and standard auto pts  That's where I bought mine, and it cleared up all the problems you are having,  There's even a video about what this part does, and its only around $ 30

 

AC delco # is 217  1685

 

other # is 89052703 o

Edited by mensanguy (see edit history)
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On 9/13/2022 at 8:11 PM, mytc05 said:

it makes me think it's maybe not an IAC issue. Not sure what else would be causing it. I have a short video of what it's doing a lot at idle, but I can't share video files on the forum. It basically pulses at stop lights pretty bad, and sitting still starts to die (or sometimes does die) when it drops below 400 RPM, and then it over revs up to say 900 RPM and then goes back down.

If you want to see if the IAC is the problem, all you have to do is hold the brake with your left foot, while it is in gear and acting up, and give it some gas with your right foot. If you can hold the RPM at a constant speed by doing that, the IAC isn't causing the problem with pulsing and the RPM dropping. The air going  through the IAC port is bypassing the throttle plate. Once you open the throttle plate quite a bit by mashing on the gas pedal you are overriding the IAC and it is pretty much out of the picture.

 

 

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7 hours ago, Ronnie said:

it makes me think it's maybe not an IAC issue. Not sure what else would be causing it. I have a short video of what it's doing a lot at idle, but I can't share video files on the forum. It basically pulses at stop lights pretty bad, and sitting still starts to die (or sometimes does die) when it drops below 400 RPM, and then it over revs up to say 900 RPM and then goes back down.

If you want to see if the IAC is the problem, all you have to do is hold the brake with your left foot, while it is in gear and acting up, and give it some gas with your right foot. If you can hold the RPM at a constant speed by doing that, the IAC isn't causing the problem with pulsing and the RPM dropping. The air going  through the IAC port is bypassing the throttle plate. Once you open the throttle plate quite a bit by mashing on the gas pedal you are overriding the IAC and it is pretty much out of the picture.

 

 

 

If I may state my 'opinion' here on this matter;  

Only 2 conditions, well maybe 3 but let's look at the 2 most relevant. The MAP sensor 'could' be sending various erroneous signals back to the SMEC (Engine controller) which would cause the engine idle RPM to vary, or the throttle position sensor could be causing those erroneous signals. The 3rd possibility could be a loose plastic HALL effect 'shutter' plate in the distributor which could cause this as well.

We have been discussing this issue for nearly a month and I'm surprised that the owner/driver has not sought out someone with a OBD-1 diagnostic tester such as the Snap-On 2500. For all we know, we have already touched on the culprit or given the answer yet there has been no resolution. It would appear that this vehicle will need to see a professional and their diagnostic equipment. There must be some other TC owner who lives near this fellow who has a local mechanic to recommend . Is 'mytc05' a member of the TC America Club? There are club members all over the country who could recommend a repair facility if we knew who and where this individual is and where they live.

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  • 3 months later...

Hey guys,

Apologies on the delay. It's been a crazy fall, with many projects. Also ended up having to put a new radiator in this TC. So, it's been keeping me busy. I did end up putting a new IAC in the car, and still same problems. I reset the codes, and it still occasionally throws the same fault codes (12, 24 and I did get a 17 once). The previous owner mentioned he had replaced the TPS and the IAC in the past, but it sounds like his mechanic wasn't the greatest and took him for a ride a bit. So, since the car was showing the classic signs for those parts potentially being bad, and with the error codes, I put new of both in. It also has a new fuel filter that was put in right before I got it. 

 

The damndest thing about it, is it runs great when it's not acting up, occasionally. Other times, it'll idle great at a stoplight for a while, and then all of a sudden starting raving or pulsing back and forth. It also still dies on me occasionally at low speeds and idle, though that is rare. Still the same thing where sometimes I'll hit the accelerator about 1/2 way down, and it'll barely respond for a second or two and then ramp up. Never have had this issue with my other TC. And with the TPS and IAC now being replaced again, I'm at a loss. Worried it could be the ECM, which I do not want to have to replace due to cost, and not knowing if it is even the culprit. Though it is probably another issue (maybe transmission), it also will occasionally jerk a bit repeatedly when driven at a consistent 45-50 mph. My dad will be in town for the holidays, and can take another look you all recommend he look at other potential culprits. Any other suggestions, gents? 

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"Let us not keep beating the same old horse"

From all the correspondence since August 30th, you have given us trouble codes 12=BATTERY FEED TO ECM, 24=THROTTLE POSITION SENSOR, AND 21 [WHICH IS OUT OF SEQUENCE AND WOULD NOT READ OUT THAT WAY] 21= IF NO OXYGEN SENSOR READING FOR MORE THAN 22 SECONDS WHEN IN CLOSED LOOP. It is likely NOT that.

 

Something that can give out codes for VACUUM SIGNAL abnormalities and OUTPUT VOLTAGES out of range, but seldom set a code when the vehicle is operating nearly normally is the M.A.P. SENSOR. 

It can produce that very drivability problem you are experiencing. It controls the amount of fuel, in milliseconds, that the injectors spray fuel. With the lightest variation in vacuum signal, which is controlled by your foot on the accelerator pedal, the MAP sensor could be cutting out fuel delivery altogether if it was defective.  I'm not telling you that it is bad, but it is a plausible possibility. Here again, an appropriate diagnostic tester could verify the problem or eliminate the sensor from that possibility.  If you do go for a MAP sensor, be sure you get the correct one, check the old one for a part number such as on this one which I have marked BAD.

 IMG_4440.jpeg.016d27a0bf9a791d83a385b70a88d06c.jpeg

If there is no part number on the sensor, verify that the replacement sensor is the appropriate one for your application. RockAuto has one 'WALKER 2251006' which corresponds with this bad one from a 2.2L Turbo '89 TC.

Edited by Hemi Dude
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I agree with hemi completely, in that he has a lifetime of troubleshooting these engines.

The only thing I could offer is to check and REPLACE all of your vacuum lines and fittings.

While they may LOOK good, they can be soft, have slits/cracks in them that bleed, or any number of other failures.

And in a 30+year old engine, that means 30+ year old hoses, which have a finite life. 

Not hard to do, or expensive either. Just do one at a time, and reference the EPA sticker.

 

I cant tell you the number of drivability problems I have remedied with this simple process.

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On 12/20/2022 at 7:14 PM, mensanguy said:

I agree with hemi completely, in that he has a lifetime of troubleshooting these engines.

The only thing I could offer is to check and REPLACE all of your vacuum lines and fittings.

While they may LOOK good, they can be soft, have slits/cracks in them that bleed, or any number of other failures.

And in a 30+year old engine, that means 30+ year old hoses, which have a finite life. 

Not hard to do, or expensive either. Just do one at a time, and reference the EPA sticker.

 

I cant tell you the number of drivability problems I have remedied with this simple process.

Hey gents. I agree with you @mensanguy, about @Hemi Dude. I know he's got a ton of experience, not only with Mopar in general, but specifically our T.C.'s. A little background on my dad. He was a Chrysler technician for years as well, before becoming a service manager and then eventually having his own Chrysler dealership for a while. So, often, the things that are recommended on here, he's already looked at and tried. However, since these T.C.'s can be a little tricky on their own, and with Dad being out of the field for years, he always values the input you guys provide, as sometimes, things will be something he hadn't seen before that are unique to the T.C.'s or that he just hadn't thought of. I just have to be the relay in-between, since I have more time to work on it, and do the posting. So, I do what I can and then default to him when I'm visiting them and he can take a look. So, a big THANK YOU to you guys for your help on different issues over the years!

 

That said, I did check with Dad, and he had pulled the MAP sensor off of another V6 T.C. when I first got the car and it was having these issues, to see if it fixed the problem. While it did improve some of the problems with it running, this particular issue remains. Perhaps that old sensor was at least partially faulty as well. So, it might be worth a try replacing it with a new aftermarket MAP sensor. That is a good suggestion with the vac lines as well. We're going to try to take a look at that tomorrow while he's in town for the holidays. It just runs great when it's not acting up. So, I feel like it's always on the cusp of bing a reliable daily driver. Just gotta get this one figured out. I'm going to try to take it up to get the fault codes read by a DRB as well. Will let you know what we find. Thanks guys!

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"A little background on my dad. He was a Chrysler technician for years as well, before becoming a service manager and then eventually having his own Chrysler dealership for a while."

Say "Hi" to your dad from me. Having been with various dealers across the country, I've had similar experiences as your dad, general mechanic, for a long time the TRANNY rebuilder, Service manager at several dealerships, but I prefer being the shop 'troubleshooter' as that is the most challenging, from the vehicle perspective.

Service Manager is definitely the most challenging from the customer perspective and one I frankly HATED.

Most new owners don't want to hear the words, "That's just the way this car idles"  or   You owned a Cadillac previously and now you bought a 5Th Avenue?  What did you expect, an Imperial?  They were not any better than a 5Th Ave and frankly the '81-'83 Imperial was like dealing with the TC when it showed up in '89.  Gee! Some awesome memories there.  I liked it when they brought Mannix's Dodge Dart in for service. Then he switched to the "FISH" which got serviced across the street at the C/P Dealer. Oh well, that was 53 years ago, Interesting I ran across this car just today. IMG_4457.jpeg.92927570afd3e3147532d071a801491e.jpeg

 

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This was my favorite car to work on when John S. brought it to my shop for service. I'ts for sure not a TC but it's the end of the year and if I get banned for the rest of the year for putting up its pictures, so be it.

 

286546684_Generalathome.jpeg.5c7c44e3db3193478b07da1bfd5fdb83.jpeg  JCFW2932.jpeg.0c46f5a84450fdebfed4867e39235b1f.jpeg

CUZA8436.jpeg.1a9e6f4122be694aec5f1901946b9808.jpeg

 

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That's awesome @Hemi Dude. Yeah, my grandfather was a Plymouth dealer going back to the 1960's, and then soon after, Chrysler and Dodge, and eventually Jeep/Eagle as well. So, Dad started off working at his dealership from the ground up until he eventually purchased his own, which he later sold and changed industries. Grandpa retired a few years ago and sold his dealership. So, we no longer have access to the large library of great tools (not to mention the lifts) that we used for so many years.

 

Dad just unplugged the vacuum line off the throttle body, which he said if there's a leak somewhere, it should make the problem worse. Instead, it actually ran a bit better. So, he said he doesn't think it's a vacuum leak problem. He said because of this, it seems that its actually getting too much fuel for the air mixture. Next, we swapped yet another MAP sensor off of another TC (it's off of a 90 V6, and this is a '91, but from what I understand. the 91's were just rebadged 90's that they hadn't sold yet. So they should have the same sensor). Still same problem. So, that would mean, the original MAP sensor, another MAP sensor off of a parts car I have and then this third MAP sensor have all been tried, without a resolution to the problem. That's not to say that I didn't have 3 bad MAP sensors, but I would think that would be pretty rare to happen. Dad is currently checking the distributor issue that you mentioned previously. The only other thing we can think of would be a bad ECM. When I first got this car, it wouldn't stay running at all. So, we swapped the ECM from the 1990 parts car I had onto this 1991 (again, same as above, I'm assuming it should be the same for both model years). So, maybe both ECM's were bad, but again, I would think that would be unlikely. I'm really hoping to not have to replace the ECM/have it rebuilt as I think that can get expensive.

 

Anything else you can think of, or any light you can shed on the above information? Much appreciated @Hemi Dude and @mensanguy, and hope your areas are coming out of this deep freeze over the last week!

Edited by mytc05 (see edit history)
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6 minutes ago, mytc05 said:

That's awesome @Hemi Dude. Yeah, my grandfather was a Plymouth dealer going back to the 1960's, and then soon after, Chrysler and Dodge, and eventually Jeep/Eagle as well. So, Dad started off working at his dealership from the ground up until he eventually purchased his own, which he later sold and changed industries. Grandpa retired a few years ago and sold his dealership. So, we no longer have access to the large library of great tools (not to mention the lifts) that we used for so many years.

 

Dad just unplugged the vacuum line off the throttle body, which he said if there's a leak somewhere, it should make the problem worse. Instead, it actually ran a bit better. So, he said he doesn't think it's a vacuum leak problem. He said because of this, it seems that its actually getting too much fuel for the air mixture. Next, we swapped yet another MAP sensor off of another TC (it's off of a 90 V6, and this is a '91, but from what I understand. the 91's were just rebadged 90's that they hadn't sold yet. So they should have the same sensor). Still same problem. So, that would mean, the original MAP sensor, another MAP sensor off of a parts car I have and then this third MAP sensor have all been tried, without a resolution to the problem. That's not to say that I didn't have 3 bad MAP sensors, but I would think that would be pretty rare to happen. Dad is currently checking the distributor issue that you mentioned previously. The only other thing we can think of would be a bad ECM. When I first got this car, it wouldn't stay running at all. So, we swapped the ECM from the 1990 parts car I had onto this 1991 (again, same as above, I'm assuming it should be the same for both model years). So, maybe both ECM's were bad, but again, I would think that would be unlikely. I'm really hoping to not have to replace the ECM/have it rebuilt as I think that can get expensive.

 

Anything else you can think of, or any light you can shed on the above information? Much appreciated @Hemi Dude and @mensanguy, and hope your areas are coming out of this deep freeze over the last week!

Hey guys. Dad, just checked the distributor issue you mentioned, and he doesn't see any issues with it. 

Edited by mytc05 (see edit history)
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  • 3 weeks later...

@Hemi Dude@mensanguy Hey gents,

Wanted to check back about this to make sure you saw the above 2 comments, with another little update as well. I have been driving it for a couple weeks with that swapped MAP sensor, and same problems. It does tend to idle a bit higher now most of the time, more around 800 RPM, which seems better, but still occasionally dies and revs up and down. Another strange little quirk that I've noticed with this issue. If I put it in park when it's acting up like this, it often tends to rev up (to 1300-1500 RPM) and stay there for a while. Don't know why this would cause this, but thought I'd throw it out there. It was driving like crap the other night and threw the check engine light on again. So, I checked the codes right away when I got to my destination and got the following sequence in this order, which is a bit different than I usually get:

12 24 17 14 15 55

 

The 17 I've only gotten more recently, which seems to have occurred after I replace the radiator about 2 months ago. So, I'm going to put a new thermostat in, but this driving issue has been happening since well before that ever showed up. Is it weird for the codes to read out out of numerical order like that? I've also never gotten the code 15 before on this TC, which the book says is a "vehicle distance sensor circuit". I talked to my Dad about it, and he told me the output speed sensor could be going bad. When I told him the speedometer has stopped workin on me a few times lately for a few minutes each time, he said that would make sense. So, I'm going to try to replace that sensor. I wonder if this could be causing these issues, even though the speedometer itself has only more recently stopped working temporarily here and there? 24 is, of course, that same TPS code, and 14 is that same "MAP sensor electrical circuit", which of course, I've replaced both the TPS and MAP sensor multiple times. So, it might be something in the circuits, but not the actual sensors? Any other recommendations gents? Again, hoping it's not an ECM issue as I mentioned above, and don't know how to even know for sure if it is that. Thank you guys for your patience with this along the way, as I know this has been ongoing for a few months now. Let me know your thoughts. Thanks!

 

Edited by mytc05 (see edit history)
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