Hey there, I was wondering if a missing bolt would cause the ground circuit to malfunction? A while back I was trying to find an issue with intermittent stalling on my ‘90 Cutlass Supreme and changed the ignition coil packs. One of the bolts was a real bitch to get to and the coils feel really sturdy on there so I opted not to put the last bolt back in.

Fast forward a bit, and I’ve figured out it was the fuel pressure regulator and MAP sensor that had gone bad. However, the car is still stalling and having issues starting intermittently, even though the fuel pressure is good now. I’ve tried a dozen other things, and I’m starting to wonder if that missing bolt might be causing the coils to malfunction one way or another? Thanks much!

 

It would be to your benefit to identify the model & year.

 

I edited the post, it’s a 1990 Cutlass Supreme. Sorry about that, thank you!

 

Hey there, I drive a ‘90 cutlass with 36k miles on it and have been trying to track down an issue with stalling for a while now. The issue started only stalling at red lights, never while driving. We eventually did the ignition coil packs and left a bolt off because it was a bitch to get to and they were pretty snug on there. Afterwards we tested fuel pressure, found it to be low, and replaced the FPR and MAP sensor. Fuel pressure has been fine since. However, it still stalls while driving and has a hard time starting. Here’s a list of things we’ve done:

-fuel filter
-spark plugs and wires
-FPR
-MAP sensor
-ECT sensor
-Crank sensor
-ignition coils
-checked air filter
-cleaned throttle body

My only idea at this point is that the original issue was fuel pressure, but we created a new issue by leaving the bolt off. Maybe it’s disrupting the ground connection? That’s a stretch but it’s really all I’ve got. Any advice or direction would be greatly appreciated. Thank you much!

 

Are you using a fuel pressure gauge to test fuel pressure? What is the actual pressure when the stall occurs? Have you tested fuel flow?

 

Engine size?

 

Any codes? IT still can have codes without a CEL.

Pat

 

Also, did you just replace the ignition coils and sensors with parts store cheapies? They have a pretty abysmal reputation.

 

There is a bolt under the ignition coils and coil pedestal on the 3.8l Series 2 V6 in my 96 98. It's a PITA to get to but it's ESSENTIAL. As I recall, there's a ground wire for the coils running to one of those bolts. I repaired the eyelet on the ground wire because the jacket and terminal were damaged.

 

Does anyone have a picture of the engine mount arrangement for this vehicle? Many GM vehicles of this vintage had a top front engine mount commonly referred to as a "dogbone". It had an eye boss on its underside and a provision to insert a pry bar. You could remove the through bolt and pry (roll) the engine forward, then insert the through bolt into the eye, thus giving you increased access to the coil packs.

 

It’s a 3.1 liter V6

 

That gives me hope, mine isn’t a 3.8 but that tells me it’s not impossible. The bolt in question isn’t directly connected to the ground wire, do you think it still might interfere with the connection? Thank you!

 

I think my engine has a mechanism that either allows it to slide forward or roll forward, but either way the coils packs are on the front face of the engine. Would it be possibly to pry it the other way, or is it not designed to go either way? Thanks much!

 

For the sake of simplicity I didn’t mention that after the FPR I took it to a shop because my buddy that helps me was out of town. Initially it had low fuel pressure but according to the mechanic it’s been 40-45 since the MAP sensor, and always has fuel pressure when it’s acting up. I really trust him, but I might test it myself just to rule it out 100%.

 

I’m sorry I’m fairly new to cars, I didn’t even know you could have codes without a CEL light. I’ll go ahead and check to be sure, thank you!

 

Nope, I recall you saying something similar a while back and personally suggesting NGK so we went with those. Though if the ground connection is bad from that missing bolt do you think it would damage the new coil packs and demand another replacement? Thanks much!

 

You can have coils tested at the auto parts store. Get them tested before you replace them.

 

Will do, I appreciate your help.

 

I merged the threads. Let us know what you find out when you get the coils tested.

 

Diagnosing intermittent stalling/cranks no start issues can be frustrating. Throwing random parts at the problem is expensive and seldom corrects the problem. Having a systematic diagnostic plan can reduce your frustration. This was my plan of attack when I was faced with customer's complaints such as yours.
I would be looking at these three conditions when the problem occurs.
Spark from the ignition system at the end of the spark plug wire(s).
Fuel pressure and flow.
Fuel injector pulse at the fuel injector connector(s).
To do this I would place a connected fuel pressure gauge under the windshield wiper blade so I can monitor the fuel pressure while driving. I would have with me an ignition spark tester and a noid light. I would operate the vehicle until the stall occurs. Road test the vehicle until the stall/no start occurs. When the problem occurs:
Read the fuel pressure and test the fuel flow.
Connect the spark tester, test the ignition system output at the spark plug end of the ignition wire(s).
Connect the noid light to at least one fuel injector connector on each bank of the engine (left and right side of the engine) and test for fuel injection pulse.
In my experience I have found at least one or more of these systems not working:
Low or no fuel pressure and/or low fuel flow. Usually caused by a fuel pump that stops running intermittently.
No ignition system output. Usually caused by a ignition module that fails intermittently.
No fuel injection pulse. Further diagnosis needed. See below
No ignition system output and no fuel injection pulse. Might be caused by a crankshaft position sensor and least likely a failing engine control module.
If all of these systems are working, unplug the mass air flow sensor. If the engine starts it may run ruff and the fuel mixture may be very rich possibly with black smoke and rich fuel smell from the tail pipe.
There are three there items that can be "tap tested" with the engine at operating temperature and running at idle speed in your driveway:
Using a screw driver handle tap the air flow sensor several times. If the engine stumbles of stalls you may have a failing air flow sensor.
Using the palm of your hand smack the engine control module several times. If the engine stalls or stumbles you may have a failing engine control module caused by poor connection or cracked circuit board that opens when it gets hot. (same for the air mass meter)
Using a screwdriver with a shank long enough to reach the crankshaft position sensor mount bracket tap the bracket several times. The bracket is cast aluminum so be gentle. If the engine stalls or stumbles you may have a failing crankshaft position sensor.
Flex and pull the engine control system wiring harnesses. If the engine stumbles or stalls you may have a damaged wire harness or poor connection(s).
To continue further I strongly suggest you obtain the factory GM service manual for Engine Performance Diagnosis for your make, model, year and engine code (the eight digit of your VIN). In this manual you will find diagnostic flow charts. Find the flow chart for stalling/no start in the beginning of the Engine Performance section. The chart description label should start with an "A". (A1, A2, etc.)
My last suggestion is to use only GM or AC Delco replacement parts.
I hope this helps, please keep us appraised of your progress and finial solution.

 

Hey there, and thank you all for your help thus far.

Today I went out there and put that missing bolt back in, which as far as I could tell made little to no difference, or at least not immediately. I’m gonna be having a good family friend of mine take a look at it at some time soon, I think having a fresh set of eyes will help. Considering that the fuel pressure is good and ignition system is well tuned up at this point, the only thing that comes to mind is the throttle position sensor.

I’ll get the ignition coils tested at some point soon, but I just have my doubts that it’s anything to do with them at this point.

Thank you all again, I’m really at my wits end. I’m determined to get her running as well as she did before though!

 

Actually, a crank positioning sensor comes to mind. You have to support the engine with a floor jack and remove the motor mount to install a new serpentine belt. The crank positioning sensor is near the motor mount. I damaged the one on my 3.8l v6 in my 96 98 when I replaced the belt. Thankfully, it still works.

Let us know if your friend has any luck.

 

Is it petering out or abruptly stalling like the key is being turned off?

I used to clean the egr valves out on those 60° motors frequently. if its stuck open it'll chug like it has a big camshaft. It'll stall out eventually but you'll have plenty of warning that it's going to stall.

 

I’ve done the crank sensor, unfortunately no dice there. I’m thinking the throttle position sensor for a few reasons. Sometimes it’ll accelerate by itself at idle, jerk a bit while driving, and generally idles terribly. Also could be in my head, but I think it’s taking a bit long to shift gears, and also has less power. I’m thinking if it’s failing to tell the car when the plates fully closed it’ll cause it to either run rich or eventually stall.

Will definitely keep this thread alive, you all have been massively helpful. Thank you

 

Sometimes it’ll stutter a bit before stalling, but generally it just goes out. The other day was actually the weirdest, it kept running so long as I repeatedly pressed down on the accelerator, but wouldnt respond to holding it down. Granted it didn’t really run so much as just inch forward though lol.

 

Your symptoms sound more and more like a stuck EGR or the stove pipe from the valve to the intake plenum is cracked. A stuck egr is a massive vacuum leak that cant be heard, and can account for most of your symptoms.

 

Gotcha. I’ll go ahead and clean it. If it helps but doesn’t fix the problem I’ll replace it. Thank you!

 

Hey all, thanks again for your help so far.

I had my buddy look at it today and go through some trouble shooting. In a nutshell, we found that spraying starting fluid helps the engine run, but there’s pressure at the rails so as far as I can tell that means the fuel injectors are just failing to fire. I don’t think bad/clogged injectors would be intermittent like this, and even if they were I used some injector cleaner not too long ago. Any suggestions on what could cause this? Only thing that comes to mind is various sensors, but I’d hate to shotgun parts at it.

thank you as always, you all have been a great help!

 

What is the PSI reading at the rails as indicated by a gauge while the problem is occurring?

 

40-45 psi

 

Have you tried to ID a possible vacuum leak?

 

I listened around for a hissing noise, but I didn’t hear anything. I didn’t think a vacuum leak would be intermittent and specifically act up when hot. I’ll go ahead and check for one though.

Thank you!

 

Have you pulled the egr yet? You might be limited as to what you'll see. I believe in those years the EGR was not vacuum operated, it was controlled by the ECM. I remember having to use the scan tool to command it open and close and make sure it had the proper range of motion.

 

Ive not, I actually just took it to a pretty well recommended mechanic who specializes in older cars. I made sure to bring it up to him, but it is in his hands now. Thank you!

 

Hey there, and once again, I’d like to thank you all for your help. It’s been a fun adventure learning as much as I have and getting to be in touch with the olds community a bit.

I’ve just taken it to a pretty well recommended mechanic who specializes in older vehicles. Generally does even older muscle cars and classics, but he definitely knows his way around these motors. It’s a good feeling to leave it in someone else’s hands, and hopefully this issue will be solved for good after the past two or three months of working at it.

Im sure I’ll reach out on here again soon enough, but for now I’d like to wrap this thread up with an expression of gratitude. Take care folks, hopefully I’ll know enough to help you guys out one day. Good luck with the projects!

 

Was there any resolution to this?

 

Looks to be bad wiring or a bad ECM. The return voltage from the MAP Sensor to the ECM is off, even after replacing the sensor. Guy I took it to said he’s stripped it down and followed the wiring, but it didn’t look terrible so he’s leaning towards an ecm. He seems to be much better at troubleshooting and working quickly than the guys I took it to before

 

That's good you got a definitive answer. I actually replaced an ECM in a 93 Buick LeSabre I owned because of a quad-driver module failure. After replacing the ECM the trouble light went away.

 

how bad are ecms to replace in those kinds of cars? We were thinking about doing it ourselves but figured we’d be better off letting him take care of it

 

I replaced the ECM in the parking lot of the first apartment my wife and I rented. On that Buick LeSabre it was located along the driver's side front fender near the airbox (the same place where the OBD 2 ECM is in my 96 98). My dad; Oldsguy, worked at a radio repair shop at the time and we used an ESD mat and grounding bracelet when we replaced it.

This was probably in 2003, so I found the ECM easily in the salvage yard. Use this search engine to look for possible parts cars near you. I'd start my search nationwide.

http://www.car-part.com/

If you have the mechanic replace it just ask him if he plans on using an ESD mat. Those OBD 1 ECMs are pretty hardy and just use basic solid state boards, but it doesn't hurt to be careful.