Buick Reatta runing rough

[rben]

So i replaced, cam sensor, crank sensor, coil pack, ICM, and the MAF. Checked the voltage on the sensors and  the pressure of the gas line. all are good but it is still running rough and the RPMs jumping up to 6000 for a second as it runs. Also the cad converter gets red hot do to the missing and back firing. So i am believing the  the timing has jumped a tooth. anyone have another idea or is it time to tear out/repair the timing?

[DAVES89]

Oxygen sensor and spark plug wires. 

[rben]

i am going down that road. i pulled the oxygen sensor and started it, it ran as it usually does. then i put the sensor back in and it ran as it usually does.  One other thing i was looking and found the RPM gauge has a 0-6375 limit. 6375 is the reading it jumps to every so often. the engine does not sound like it jumps that high. it is only for a second i see that value.

[DAVES89]

Usually a bad oxygen sensor makes the cat turn red but if you want to do the timing chain first, good for you.

 And bad wires will give you a rough idle. So does not cleaning the idle control  sensor and the casting it fits into...

[Ronnie]

You don't give any background on how this problem started so it's hard to just guess at what might be wrong.  Part of troubleshooting is knowing the recent history of what is going on with the car.  Any chance that you have crossed the spark plug wires while swapping parts?  Are any codes showing in diagnostics?

[rben]

So i posted before about this Buick. Thus far i have changed out the Oxygen sensor, cam sensor, crank sensor, coil pack (twice), MAF sensor, and ECM.

Background, i parked it at the airport for a couple days in August when it was really hot. It started hard, which was unusual, and has been messed ever since. It starts every time and runs, the battery is a POS, so that does not help. Meanwhile, it runs and does not give off any codes other than ones induced when i unplug things.  As it runs the engine misses a little and the tac shows 6375 (the max it can display) about once every 25-30 seconds. the engine revs up and down like someone is purposely rev it up and down just a little. The tac thing sort of throws me, it shows that high rev but it does not sound like it is revving that high.

I have run it with the MAF sensor pulled, with little change but there is change. With cam sensor or crack sensor unplugged it will not start. Remove the oxygen sensor and it will run about the same as it does with it connected and mounted correctly. Removing the oil cap and nothing changes. I removed the plug wires one at a lime as it ran with little change and spark at every plug of the coil pack. It does backfire but not very often.

So i am trying to see if there is something else i missed. I am at the point of doing a motor swap but i want to be sure it is not an electrical issue, making a swap pointless. I suspect the timing jumped just enough to make it run, while it tries to correct itself. Thus the backfiring and funny revving?

[2seater]

The tach. signal comes from the ICM. Sometimes it is hard to sort out which is the cause or the effect. Case in point, the rolling idle, is it trying to stabilize the engine or is the unstable idle real? Do the IAC counts ramp up and down while the idle changes and if they do, do they lead or follow the speed change? The engine should definitely be able to start and run with the cam sensor disconnected. I do not know of a reliable method of checking for timing chain issues save for opening the front cover. You could try observing the cam magnet with the sensor removed and rock the crank back and forth to see how much lag in the cam movement but the presence of the chain tensioner muddies that a bit and still doesn't answer the root question if the chain is off by a tooth. 

[Ronnie]

15 hours ago, 2seater said:

Case in point, the rolling idle, is it trying to stabilize the engine or is the unstable idle real?

 

Would unplugging the IAC while the engine is idling answer that question?  Seems like the idle should remain constant as long as nothing puts a load on the engine like the AC compressor kicking in etc.

[2seater]

12 minutes ago, Ronnie said:

 

Would unplugging the IAC while the engine is idling answer that question?  Seems like the idle should remain constant as long as nothing puts a load on the engine like the AC compressor kicking in etc.

That sounds logical to me. 

 

I imagine the ECM has other tools to accommodate engine load also, like changing ignition timing. I usually see a 2-3degree jump in timing just taking the car out of park to in gear. What signals this I do not know, but just my observation.

[Ronnie]

I was just thinking that maybe adjusting the IAC in diagnostics to a certain RPM, for example 800, and then observing how stable the RPM remains might work just as well as unplugging the IAC.  I might do some experimenting this afternoon just for the fun of it to see what happens.

[Ronnie]

2 hours ago, Ronnie said:

I might do some experimenting this afternoon just for the fun of it to see what happens.

 

Here is what I found.

 

I began by starting the car cold from sitting overnight.  When I started it I looked at the gauges and the RPM was steady at 800. Then I went straight to Diagnostic->ECM->Overrides.  Using ES09 (IAC Motor) I ran the RPM a little higher. I'm guessing 900-1000 since I couldn't access the gauges screen to know for sure. 

 

Then I sat there staring at the CRT the whole time until the ECM went into closed loop and O2 sensor indicator began to flash. During the entire time the engine was warming up and after it went into closed loop the idle was as smooth as silk and no RPM fluctuation was detected by my highly calibrated ears. 🤣 Turning the steering wheel to load the power steering pump didn't seem to affect the RPM much but I could tell the sound of the engine changed a little.  When I shut the engine off and restarted the RPM settled in at a smooth 750-775 RPM. You couldn't tell the RPM was changing without looking at the gauges.

 

I don't know if this little experiment will be useful to anyone or not but I wanted to know myself for future reference. 

 

Something new I did learn is that the SES light only flashes about half as fast after the ECM goes into closed loop as it does when in open loop.  That might be useful to know when trying to troubleshoot a problem and you can't access diagnostics.

Edited November 12, 2019 by Ronnie (see edit history)

[2seater]

Good observations for sure. Experimentation like that may not be immediately useful but filed away in the memory banks, right next to the highly calibrated ears, might give a leg up if the car does something unexpected. I sometimes rap on an engine bracket with the engine idling to see if I can get a stumble from knock retard just to be sure the system is working as I regularly get into knock sensitive conditions.

[padgett]

Just a noter but if the ECM was getting a 6375 rpm signal it would chop the fuel and you would feel a miss. If not it is in the tach readout circuit. What is ED11 showing when it happens ?

[rben]

i am back, took the car to a local shop and they had it for a week. They said they had it running good and then it would go back to the "rough" state. They tapped on the ECM at one point and it went good again. So they replace the ECM and said it took care of the issue. I got i t home and let it get warm to see if it was good and stared stalling out. I put some new gas in it and drove it around the next day and it did not stall out. I am not completely believing it is good but i dont want to drive it too much with out the shock connected to the motor on the passenger side. I have been looking to replace it but not finding a new one. Anyone know if this is a "needed" item or where i can get a new one?

[padgett]

My 88 does not have the shock.

 

Sounds like they were just throwing parts at it. Problem is that very few people know how to troubleshoot a 30 year old ALDL car. Takes an adapter, special program (TunerProRT) and map of the parameters (TunerCat).

 

Then you can monitor while driving and store the run for later review. Often an issue will jump out at you. Helps to have a domesticated Nerd.

 

 

[dship]

On ‎2‎/‎23‎/‎2020 at 6:41 PM, rben said:

.....but i dont want to drive it too much with out the shock connected to the motor on the passenger side. I have been looking to replace it but not finding a new one. Anyone know if this is a "needed" item or where i can get a new one?

I believe the mini shock you're looking for is called a "vibration absorber", and they're very hard (if not impossible) to find.  Check with the vendors listed on this Reatta forum.  They are somewhat not needed, but without one the engine mounts will have to absorb more of the vibration. 

Edited February 26, 2020 by Dave Shipman (see edit history)

[rogold99]

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=Stabilus+123-240-23-48&_sacat=0

 

I think this is what you are asking for.

Edited February 25, 2020 by rogold99 (see edit history)

[DAVES89]

I believe 63viking came up with a replacement. maybe he will respond with an answer.

[rben]

during my search for the "vibration dampener" i found one on Ebay for a 1991 Reatta. It was called a "vibration dampener"  but it was the harmonic balancer with a rubber ring mount on the back of it.

[dship]

From the 1986-1993 GM Buick E Body Parts & Illustration Catalogue:

Called a Vibration Absorber and fits 1991 E97 (Reatta) and 1992/1993 E57 (Riviera), part # 3520659.

 

I believe a compatible replacement might be from manufacture Stabilus; an engine shock damper/torque strut, part # 1232402348 or 2012400248 or SG-403004 which are for a Mercedes.  You can find them on eBay but look at the pic's and compare to what's on your Reatta.     

[padgett]

Length, diameter,  and mounts are all that really matter.

[rben]

Well so much for it running good. Took for few miles yesterday and it stalled out. drove home and it stalled another 4 times. each time it started up and ran fine for a bit. the last time i was watching the gauges and the RPM maxed out, then it stalled with an electrical fault message. Now it turns over but never starts.  So i guess to start at the fuel and g from there. anyone seen this issue before?

[padgett]

With the gauges wonkey I'd look for a ground problem particularly the engine <> chassis ground wire.

[rben]

my thought as well, at the same time figure out why it wont start. checking all the options behind that.

[rben]

so here is what i have so far. I shot some starting fluid through the air take and it ran for bit. That tells me the spark is good. Then i forced the fuel pump to run but that it did not start. So that still leaves me with a couple things. Are the injectors working? Am i getting fuel pressure? i suspect the injectors first because i could feel and hear noise in the fuel system. So, what controls the injectors?

[2seater]

38 minutes ago, rben said:

so here is what i have so far. I shot some starting fluid through the air take and it ran for bit. That tells me the spark is good. Then i forced the fuel pump to run but that it did not start. So that still leaves me with a couple things. Are the injectors working? Am i getting fuel pressure? i suspect the injectors first because i could feel and hear noise in the fuel system. So, what controls the injectors?

ECM runs the injectors but must have adequate fuel pressure first. Hearing the fuel pump run should be a good sign but, if it isn't producing adequate pressure, it won't run. Need to get a pressure reading if fuel delivery is suspect. One note on spark is; the ECM controls spark timing once running but the initial startup is done through the crank sensor and ICM under the coils. Injector operating system is simple although the control is not: injectors are supplied a constant 12v when the ignition is in run, the brown wire to each injector if memory serves and the ECM provides the timed grounding on the other wire to complete the circuit and open the injector. 

[rben]

Well few (hundred) dollars later and it runs, mostly. New ECM, ICM, Coil pack, Cam senor, Crank sensor, O2 sensor, and Mass air sensor. So now it runs and sometimes stumbles like it is missing. watching oil pressure and its jumping about even while sitting idle (34-41) psi. This does not seem right, at the same time there is a notable hole in the exhaust. Any of these items make it run like it is missing? 

[padgett]

If here I'd put an ignition scope on it. Easiest way to analyze an ignition.

Not conferned about oil pressure, just need some. What is the fuel pressure doing ? Any gas in the regulator hose ?

[rben]

well i currently dont have a way to check the fuel pressure. There is no fuel leaking which would mean the check valve is "ok" but at the same time... if i disconnect the vacuum line to it, here is not change in how it runs. i did however find that it runs better if the Mass flow sensor is unplugged.  A side question, what temperature does the cooling fans come on?

 I found mine run over 200 before kicking in. Plus it is both fans not just one. i tested the relays using the CRT and they come on using "over-ride", one at a time. but when using the output test with "hi" and "Lo", lo does nothing it only runs on high.  its almost like the parameters are set wrong or something.

[padgett]

I reprogrammed mine to come in at 185/190 stock it is over 200 unless the AC is on.

88 one fan is on at low, 89-91 both are at half speed for low.

To measure the fuel line pressure you attach a fuel pressure gauge.

 

/rant/To really enjoy a 30 year old car you need to be able to perform at least simple maintenance or have a full wallet for someone else to learn what a Reatta is. ODB-II has been around for a generation now so few remember the ALDL predecessor. Alsomost no-one who does not have one knows how to invoke the diagnstics.

 

Before GM sicced their law dogs on us we could post the service and parts manuals in .pdf form. It would not surprise me if they were still available. Was nice because then could just refer to a page in the FSM. Of course Helm only has the 1989 Shop manual ($205) when they were the ones demanding their removal from our site.

 

Perhaps it is time to renew our application to post unavailable manuals.

 

 

 

[rben]

padgett, just read -up on your site and see a note of the fans. did you get them to run at a lower temperature setting?

[padgett]

Yes, you have to modify the PROM. With a 180F thermostat I have LO fan come on at 185 and HI fan at 190.

[2seater]

I had a somewhat lengthy reply from yesterday that disappeared?? In any case, I wondered the same thing about the fuel pressure and made the assumption that a competent shop that replaced a bunch of items would at least do something so rudimentary, but now I wonder. I share Pagett's concern about the modern lack of diagnosing a system from decades ago. Much can be gleaned from  the onboard diagnostics, but some things are outside of its ability, although some things can be inferred from other information. I believe in previous posts in this thread that the timing chain was suspect and was that ever looked into? I noted the comment about a "hole in the exhaust", assuming that means a noisy leak? If there is a leak near the O2 sensor, such as the rear manifold flange to head or the donut seal to the tailpipe, it can suck air in and it will fool the O2 sensor.

[padgett]

I've had posts disappear before. Usually long ones. Must be the censors.

Suspect if things were different I could open a shop catering to pre-OBD cars, still have two ignition scopes and a distributer machine plus a dial-back timing light. Also a gaggle of ALDL stuff and cartridges for other computer cars.

 

Wonder how many know how to use a breaker bar to check a timing chain ?

 

 

 

[rben]

i never did check the timing chain. the hole in the exhaust is the short piece under the cockpit just after the first 90. It might be close enough to cause some effect.

It was running odd again and made note of few things. I runs rough when the rpms are under 2200 and you just give it a little gas. If you give enough get up to speed on a ramp it seems fine. the Idle is a bit rough like a plug is bad, which is possible. I wounder though how does the fuel pressure regulator work, lower pressure at idle, more during acceleration?  it might just be good to replace it?

Here is another thing, Mass air flow sensor. i replaced it along the way but it seems to run better when it is unplugged. Is it possible i need to calibrate the feed back from the sensor?

[padgett]

Sounds almost like water in the gas. Did it sit for a while this winter ?

[rben]

 

It did at the shop, from January thru end of April while it was being worked on. I have since then filled the tank and put in some injector cleaner, i could add some dryer too.

 

[edinmass]

Fuel injector cleaner added at the tank will clean the dirt out of the tank and put it into the fuel system, bad idea....I mad a lot of money on that stuff when I had a modern shop. Don’t add the dry gas either, it will pass the water through the filter into the injectors. There is no such thing as a tune up in a can, and no easy fix.

[2seater]

There have been a few questions unanswered so far. What is the actual fuel pressure, if it runs better with MAF disconnected, do you have the old one to swap back, or even a junkyard one to try? Timing chain? How many miles?

 

In answer to the fuel pressure regulator, it responds to vacuum level in the intake manifold, the purpose being to maintain a constant pressure drop across the injector. High vacuum, such as at idle, will reduce fuel pressure, and conversely it will rise as throttle opening is increased. It is very responsive and the relationship is approx. two inches hg vacuum for each psi of fuel pressure, so mid thirties fuel pressure at idle is normal, remove the vacuum line to the regulator and pressure should be near three bar or forty three point five psi.

 

Heavy throttle beyond a certain tps voltage will cause the engine to run open loop, so the ecm will ignore some sensors and use the base fuel and timing map burned into the Prom. 

[padgett]

BTW if the diaphragm in the fuel regulator ruptures, there will be gas in the vacuum line and will not run rite.