Engine Idle

For the tech guys: '89 TC 8 valve 2.2 turbo has a sputter or miss when idling. All parts new, coil, plugs, wire, dist. cap and rotor. Throttle body was disassembled and completely cleaned. Runs fine when cruising down the road. Mechanic says throttle body had a lot of funky looking oil in it. He thinks I may need new fuel injectors or new seals in the turbo. Compression test shows all 4 cylinders at 127 lbs. pressure. No codes on computer. Any ideas what is causing this? The car did sit in an airplane hanger for about 10 years. Previous owner only put 1500 miles on it in that ten year span. I bought the car a year ago and am trying to get everything right. Any help would be greatly appreciated. Thanks, Rick

1500 miles in ten years probably means that the car averaged 5 gallons of gas a year and my guess is that the rest of the tank wasn't to fresh. You might need to hard clean the injectors, I think it's easier to replace.

Before you go that far get yourself half a dozen bottles of good injector cleaner, toss one in the tank right away, fill the tank every time it reaches half until you use up your jugs of cleaner and put a few thousand miles on the car, if that doesn't kill the sputter changing the injectors is financially justifiable.

Thank you Digger for the info. Could a bad turbo cause an engine miss, and how do I know if the turbo is not working properly?

Thank you Digger for the info. Could a bad turbo cause an engine miss, and how do I know if the turbo is not working properly?

That's a good question and it brings a question. Is the engine miss the rough idle, or is engine miss like your heart skipping a beat while you're jogging?

The turbo like a windmill driving a fan, exhaust passes through one set of fan blades and that in turn spins the fan blades on the other end of the shaft sucking up fresh air and stuffing it into the intake. Step on the gas the motor RPM's increase, turbo spins faster and you get more air pressure to the intake. These things spin really fast and when the bearings go bad it screams like a banshee, or it stops spinning and the engine runs like you crushed your exhaust pipe on a speed bump. Bad turbo shouldn't cause rough idle.

Depending on what you have for engine miss, a sticky waste gate could, or loose hose type of air leak through the inter cooler could, or it could come from sensors in the system. This kind of depends on how you are going to describe your engine miss.

Ralmon; i seem to have the exact same condition that you mention. also a 1989; 8 valve automatic. at idle it seems to sputter or miss a little but as soon as i step on the gas it is fine no sputter at all and drives fine. it is also ideling at the proper RPM but sputtering. i have replaced exactly what you have done and cleaned throttle body etc. also i cleaned all of the injectors etc. i tried to find some kind of vacume leak and i do not see any leak. this problem has got me baffled. especially with the fact that it runs perfectly when driving, no miss or sputter at all. good gas mileage and everything. my son currently has the car at college so i have not been working on it for a while, but the condition is exactly what you seem to mention. if i ever figure it out i will let you and everyone know. if you ever figure it out, please let me know. thanks a lot and happy motoring

Thanks for the response Butch91. Car is in shop now getting new fuel injectors installed. I do have the exact same problem as you do. My mechanic has tried just about everything and hopes the new fuel injectors solves the problem. If not, we do not know where to go from there. My main reason for trying to get this fixed is that I will be in the classic car parade at Cruising the Coast in Biloxi, MS in October. There is a lot of stop-go and sitting at idle along the parade route, and I want to make a good showing as this is the first year the TC's are permitted to participate. We don't want to be sputtering like an old lawn mower during the parade. If we can get it fixed, I'll let you know how we did it. We have received very good information from Digger, and hope to solve this problem soon. Ralmon

Digger, thanks once again for your help. One thing we did notice when working on the car. When checking and setting the timing, with the cooling or temp sensor disconnected, the car smoothed right out and did not sputter or miss at all. When plugged back in, sputter came right back. Could this have something to do with it?

Digger, thanks once again for your help. One thing we did notice when working on the car. When checking and setting the timing, with the cooling or temp sensor disconnected, the car smoothed right out and did not sputter or miss at all. When plugged back in, sputter came right back. Could this have something to do with it?

Heck yes, not the coolant sensor itself, but something else confusing the; or the engine control mod itself.

Had to email and call Hemi Dude several times while working on the oldest TC, never did figure out what was causing the last of the odd issues, changed both MAP and IAC at same time because the price was right, got both on closeout from Rockauto for less than regular cost of IAC, that added to the TPS that had to be changed got that 8V running idle like a old Singer sewing machine, when the new knock sensor comes in it should purr like a kitten till you tromp the gas.

You could try setting the timing back to ten, this should improve and if it gets worse you have solid symptom of sensor.

Thanks Ralmon and Digger. i did not consider the MAP or IAC as i did not get any check engine light or codes; i will look into those parts once i have the car back from my son, next time he comes home. i really would like the car to idle like the sewing machine. thanks for all your help and suggestions.

Thanks Ralmon and Digger. i did not consider the MAP or IAC as i did not get any check engine light or codes; i will look into those parts once i have the car back from my son, next time he comes home. i really would like the car to idle like the sewing machine. thanks for all your help and suggestions.

There were no codes and as the engine control would not talk to my test set, that really was a shot in the dark. I've been told this is common on some of the older ones and the one I was working on is the oldest know TC in use. Pulling the temp sens to set timing puts the car in drive home mode and over rides some sensor inputs. Could just as easily have been the O2 sensor causing the problem, but these were easier to replace and cost less on a guess. The throttle body had been thoroughly cleaned when I replaced the TPS which had a big bad dead spot, the IAC has a captured screw in a bad place to work and is risky to pull so I did not remove to scrub the seat when I cleaned the throttle body.

Really important to know whether you pull for thorough cleaning or replacement is that like the TPS, the torx head screws on the IAC are soaked with lock tight and the heads strip easily if you don't break them free on the first snap.

Put the throttle body on a good supporting surface so you can press down into the screw head when you go to break it free, do not try to turn these screws while still attached to engine, or while holding it with one hand and the screw driver with the other. You get one good shot at breaking the screw free without stripping the head and it's a lot of extra work if you don't get it done the first time.

Digger, thanks for the heads-up and the advise with regard to the torx screws. yes, i have had difficulty with stuck screws, mainly phillips in the past; can be a real pain in the neck. i do not know when i will be able to work on those items but when i do i will report the results. the baffeling part is how good the car runs when not ideling, when not ideling, it is like the sewing machine. thanks again and all the best.

Digger, thanks once again for your help. One thing we did notice when working on the car. When checking and setting the timing, with the cooling or temp sensor disconnected, the car smoothed right out and did not sputter or miss at all. When plugged back in, sputter came right back. Could this have something to do with it?

You all might have noticed that I have not replied to anything for a while. Digger does such a thorough job, you guys hardly need me any more.

As for the reason that the engine smooths out when you disconnect the COOLANT TEMPERATURE SENSOR, is because, as it was stated, it goes into 'Limp-in Mode'

(1) This sets the basic timing at whatever the distributor is set to. +10 to+12 degrees. Normally the ignition timing 'searches', advancing and retarding, which is controlled by the SMEC in order to maintain the desired idle speed.

(2) More importantly in this case, the computer goes into 'OPEN LOOP' which enriches the fuel mixture. THIS IS WHAT SMOOTHS OUT THE ENGINE IDLE that you notice.

A slow operating OXYGEN SENSOR will allow the IDLE fuel mixture to regulate too slowly, thereby being too rich momentarily and then too lean in order to compensate which results in what we call "LEAN MISFIRE".

If you are really concerned about this lean misfire then take appropriate action in order to ATTEMPT to alleviate this.

As a mechanic at the dealerships I worked at, when these cars were new, the word from the 'Factory Guys' was to tell the customer that this is a normal situation.

On my own TC with now around 275 thousand miles on the clock, I don't ever worry about this.

Keep in mind that the fuel control system on Chrysler Fuel Injected cars, all of them, is a Speed/Density system that does not have a MASS AIR FLOW SENSOR as other domestic and import automobiles have. Chrysler did it the CHEAP way, both for themselves during production and for you because you will never have to replace an expensive mass air flow sensor on your TC.

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You all might have noticed that I have not replied to anything for a while. Digger does such a thorough job, you guys hardly need me any more.

As for the reason that the engine smooths out when you disconnect the COOLANT TEMPERATURE SENSOR, is because, as it was stated, it goes into 'Limp-in Mode'

(1) This sets the basic timing at whatever the distributor is set to. +10 to+12 degrees. Normally the ignition timing 'searches', advancing and retarding, which is controlled by the SMEC in order to maintain the desired idle speed.

(2) More importantly in this case, the computer goes into 'OPEN LOOP' which enriches the fuel mixture. THIS IS WHAT SMOOTHS OUT THE ENGINE IDLE that you notice.

A slow operating OXYGEN SENSOR will allow the IDLE fuel mixture to regulate too slowly, thereby being too rich momentarily and then too lean in order to compensate which results in what we call "LEAN MISFIRE".

If you are really concerned about this lean misfire then take appropriate action in order to ATTEMPT to alleviate this.

As a mechanic at the dealerships I worked at, when these cars were new, the word from the 'Factory Guys' was to tell the customer that this is a normal situation.

On my own TC with now around 275 thousand miles on the clock, I don't ever worry about this.

Keep in mind that the fuel control system on Chrysler Fuel Injected cars, all of them, is a Speed/Density system that does not have a MASS AIR FLOW SENSOR as other domestic and import automobiles have. Chrysler did it the CHEAP way, both for themselves during production and for you because you will never have to replace an expensive mass air flow sensor on your TC.

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Hemi, don't stay gone so long, can always use your expertise. I know a lot more about motors that run with mass air flow than MAP's, Do know my way around turbos as all my Volvo's had them 4 & 5 cylinders, but I have to admit I'm much better at tweaking quad engine turbo prop than I am at tuning up a quad cylinder Chrysler and as much as I enjoy driving my TC, this is my favorite toy.

Thanks for the explanation, Hemi, I appreciate it. Would you suggest replacing the oxygen sensor as an initial step in trying to resolve this problem? Do all of the 4 cyl; 8-valve engines exhibit this particular situation? The hesitation or misfire at idle is more of an annoyance than anything else; but it just seems that it should idle as well as it runs when not at idle? </SPAN>

Thanks for the explanation, Hemi, I appreciate it. Would you suggest replacing the oxygen sensor as an initial step in trying to resolve this problem? Do all of the 4 cyl; 8-valve engines exhibit this particular situation? The hesitation or misfire at idle is more of an annoyance than anything else; but it just seems that it should idle as well as it runs when not at idle?

Yes, especially if it is the original one or you do not know if it has been replaced. The LEAN-MISSFIRE at idle is most noticeable on the turbo engines due to having individual injectors for the 4 cylinders. The TBI engines share fuel from one injector, and the fuel is delivered at the beginning of the intake manifold rather than at the point of entry to the individual intake ports in the cylinder head.

Hesitation, as you use the word, is what you would feel as you open the throttle to accelerate and it is generally caused by a defective TPS (Throttle Position Sensor)

Smoother idle on a turbo engine could be achieved with slightly retarded basic timing and also retarding the camshaft slightly.

I, on the other hand, run with timing @ +12 and the camshaft somewhat advanced. This causes a somewhat rougher idle but better high RPM performance. Since mine has a 5 speed, idle quality is not an issue as it is with an automatic.<script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/84f5bfa1/background/helpers/prefilterHelper.js"></script><script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/84f5bfa1/background/helpers/prefilterHelper.js"></script><script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/84f5bfa1/background/helpers/prefilterHelper.js"></script><script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/84f5bfa1/background/helpers/prefilterHelper.js"></script><script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/84f5bfa1/background/helpers/prefilterHelper.js"></script><script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/84f5bfa1/background/helpers/prefilterHelper.js"></script><script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/84f5bfa1/background/helpers/prefilterHelper.js"></script>

Thanks for the explanation, Hemi, I appreciate it. Would you suggest replacing the oxygen sensor as an initial step in trying to resolve this problem? Do all of the 4 cyl; 8-valve engines exhibit this particular situation? The hesitation or misfire at idle is more of an annoyance than anything else; but it just seems that it should idle as well as it runs when not at idle?

If you don't have a good torch set have the O2 sensor done, these things can get really attached to the exhaust and some get so attached that even with a torch the bung threads come out when done. Let the exhaust shop take the risk, it could be cheaper in the long run.

Thanks again Hemi and Digger

i guess i used hesitation incorrectly it is like Ralmon described, a sputter or slight mis-fire. there is absolutly no hesitation once i start to give it more gas to get going, the sputter dissapears and she runs perfectly. i will take a close look at the oxygen sensor before trying to remove. yes i am familiar with the difficulty of removing some oxygen sensors. just replaced one on the jaguar xj-6 but that one was easy to get to and did not give any real difficulty. luck of the draw i guess. Thanks for all the advice and i will keep everyone posted especially if i ever get the car purring at idle.

Thanks again Hemi and Digger

i guess i used hesitation incorrectly it is like Ralmon described, a sputter or slight mis-fire. there is absolutly no hesitation once i start to give it more gas to get going, the sputter dissapears and she runs perfectly. i will take a close look at the oxygen sensor before trying to remove. yes i am familiar with the difficulty of removing some oxygen sensors. just replaced one on the jaguar xj-6 but that one was easy to get to and did not give any real difficulty. luck of the draw i guess. Thanks for all the advice and i will keep everyone posted especially if i ever get the car purring at idle.

Most O2 sensors remove for replacement as planned, but there is a percentage (much higher up here in road salt country) of these where the bung thread becomes one with the sensor and the bung thread comes out with the sensor no matter what you do to prevent this. When that happens you need to cut the old bung off the pipe and weld on a new, if you can, or you replace the pipe. Lucky for us our TC's are old enough that the cat is not integral to the pipe so we can replace pipe without replacing the cat and vise-verse when this happens.

If you don't have a good torch set have the O2 sensor done, these things can get really attached to the exhaust and some get so attached that even with a torch the bung threads come out when done. Let the exhaust shop take the risk, it could be cheaper in the long run.

Especially on the turbo engines. Of course a good mechanic is going to quote a price for going through a lot of work.

Gentleman, you have asked for an update on my rough idle or engine miss problem. Replaced map sensor and throttle position sensor, no change. Installed new fuel injectors, plugs, plug wires, coil, distributor rotor and cap, no change. Used block tester, fluid turned yellow indicating blown head gasket. Installed new head gasket and remanufactured cylinder head. While doing this also replaced oxygen sensor. Car idles and runs very smooth now, I can even hear the turbo kick in now as before all this work I could not hear it kick in. I hope this helps some of the readers of this forum. Thanks to Hemi, Digger, Bill and Butch for all the help. Without the information I get from them this car would be gone!