Car stalls after driving awhile

[TazMan]

Hello. I'm having some trouble with my other car, not a 60 degree, but I need to get it inspected so I could really use your thoughts. It's a 1997 Olds 88 with the 3.8l V6. When I first start the car it runs great, but after it's running awhile, usually anywhere from 20 minutes to an hour, it will just stall. If I try to start it right back up it will usually just crank and not start, but if I wait 20 or 30 seconds it will start back up and go for little while, then stall and do the same thing. It doesn't matter if I'm driving or if I just leave it idling either. Once it starts acting up, sometimes the car will kind of sputter and not want to accelerate if I hit the gas hard while driving. I tried swapping out the ICM but it's still stalling. The only computer code I'm getting is for the EGR. Can a faulty EGR cause that to happen? I didn't think it would. I just drove it over 200 miles with no problem. When I got home this started happening. The next day, I took a 25 minute drive, and when I got off the expressway it stalled and I had to wait a minute or two before it would start. It's been happening ever since. Any ideas would be really appreciated. Thanks for reading.

[60dgrzbelow0]

In the absence of knowing other tests results, such as checking fuel pressure at the fuel rail port or changing the fuel filter and looking for any twisted or obstructed fuel lines, you might look at this post. Although a different GM vehicle, with the same/similar motor and bearing symptoms that are very similar to your own, perhaps this information will prove helpful. Mind you... the Original Poster is not a forum member here, and he seems a bit long-winded and emotional about the problems he was trying to solve...but his solutions seemed to have worked for his car and a look at them might be worthwhile:

http://www.grandprixforums.net/f18/3-8l-sc-random-stalls-faulty-17582.html

[TazMan]

Thanks for the link. Interesting post. I just wish it would throw a code other then EGR. I haven't checked fuel pressure or anything but the car hasn't really died long enough for me to do any troubleshooting. It always starts back up within a minute or 2.

[60dgrzbelow0]

The one variable that seems central in whatever is happening to make this problem transitory is probably... Heat. Changes in temperature can make electrical connectors expand away from contacts and break the path of the electrical flow. So it might be worth examining the MAF Meter (Sensor) on your engine. Run the engine for a while and try tapping the meter lightly... If the connections are corroded or broken, but still just barely touching (kind of like that weird light bulb in the garage that has a broken filament...but turns on and works for a minute or so until the element wires heat up and separate)...the slight vibrations you induce will make the sensor fail temporarily, just as the normal operational car vibrations and a build up of heat will do, making the engine stall out. If the engine stutters during your test... you may have isolated the problem.

[TazMan]

I'll try what you said about tapping on the MAF sensor. I was just wondering, is there any way a bad EGR could make this thing not run? Somebody told me that since I'm getting a code for it, it must be getting stuck open when I hit the gas but it happens even if I sit idling.

[60dgrzbelow0]

The short answer is: Yes.

The detailed reasons are:

The EGR is designed to introduce exhaust gas back into the intake manifold to reduce high combustion temperatures and the higher ratio of Nitrous Oxide in the exhaust stream.(See Attached Diagram). If any or all of the solenoid actuated metering valve plates in the EGR are stuck open at idle, it will allow enough oxygen depleted exhaust gas back into the intake flow to cause the engine to stall. Since the fuel/air induction in ECM controlled cars is less than solid state like the instant response of a typical Dist/Carburetor engine, think about all the other sensors that have to reach some kind of agreement before the motor will run smoothly... and all are feeding signals to a likely confused ECM unit that is trying to sort out what it all means. So you could have a combination of sensor readings not jibing correctly to suit the "mind" of the machine:

TPS
IAC
IAT
MAF
EGR
CPS (sometimes 1,2 or 3)
Cam Sensor(s)
O2S (x2...or in some cases 3 if the CAT has one)

[TazMan]

Today it stalled and didn't want to start for a couple of minutes. Still No codes since I reset the ECM a few days ago.

The EGR is designed to open up at higher rpms

Right, but would the EGR open by itself? I mean, I can start the car when it's running good, leave it idling without touching the gas, and eventually it will stall. This takes a long time though, but eventually it will stall. Now since the RPM's haven't gone above idle, I would think the EGR should never open in the first place to get stuck, right?

[60dgrzbelow0]

Its probably not a good idea to get "stuck" on the EGR as the real cause for the problem. You should probably do a really thorough job of examining each and every vacuum hose/line and the places where they connect up to the intake manifold and ancillary equipment. A car that is 21 years old is likely to have old hosing that has dried out and become brittle, tending to crack and fail at the hose ends. If you can pull each one carefully and examine their port connections and along their lengths, you night find some hidden damage. On occasion, the hose connectors themselves can be either damaged, bent, pinched or crimped and be involved in the problem, too. Failing that...you are back to the issue of testing fuel pressure at the EFI rails and the possibility that the reason the car quits at odd times may also be due to the fuel pump overheating and quitting until it cools down enough to work again.

[Talontwoswords]

The EGR is designed to open up at higher rpms and re-introduce exhaust gas that might be rich in unburnt fuel back into the intake manifold.

The EGR is designed to introduce inert gas (exhaust gas) into the combustion chamber to reduce combustion temperatures, and subsequently reduce NOx emissions.

[TazMan]

I think I might have gotten to the bottom of my problem. I borrowed a fuel pressure gauge from a buddy and connected it. At idle I have about 37-38 PSI. When I hold the gas lightly in park it jumps up to about 45 PSI for a second and then drops down to about 30, but if I drive it, the harder I press the gas the lower the pressure goes. If I floor the pedal it drops down as low as 5 psi and the car takes forever to go. It stays steady and responds well if I drive easy though. Shouldn't my pressure remain between 45 and 55 regardless of how fast I'm going or is it normal to be dropping like that?

[98oldsmobile]

I have a 98 oldsmobile 88 and my car has been doing the exact same thing as you describe with the stalling after driving about 20 minutes. After I get it started its good to go. Did you ever find out what the problem was with your oldsmobile?

[pocket-rocket]

According to his reports on his fuel pressure, I would assume either a massively clogged fuel filter, or a fuel pump. I would start with the easier to get to and much cheaper fuel filter first, for what it's worth. If it turns out to be a fuel pump, they want the filter changed for warranty reasons, anyways

BTW, welcome to the site

[Azrael]

I agree with pocket-rocket's diagnosis. Fuel pressure should be 45 psi with the throttle wide open and a few psi less at idle.

[TGP37]

I agree with Pocket and Azrael.

When you remove your old fuel filter and prove it is clogged, get a new fuel pump. Because that fuel pump WILL die very soon. Everytime I see a clogged filter get changed, the fuel pump is weeks away from failing.

Get some stuff that loosens bolts, you WILL need it. Hit the filters threaded side and let sit 6 hours, repeat for several days if you have the time. Because the fuel line is delicate and those threads are probably rusted shut. Do NOT let the fuel line become stressed while removing the filter or a simple shift will bend, kink and open up the fuel line.

Obviously, do not use a torch to loosen the threads...lol.....some people do that with out realizing.

Your vehicle was probably stalling from running WAY lean. AND the block heats up running lean as well.

Richer = cooler block / hotter exhaust
Leaner = Hotter block / cooler exhaust

When the fuel pressure drops while the rails are hot, fuel vapor pockets form and create a vapor lock scenario. If you are ever stuck like this, prime the fuel pump several time, release the vapors from the Schrader Valve, unplug the FPR and block the vac line. This should be enough to get you home.

Another test that will prove it is the fuel filter or pump is this......

Let the car idle then floor it in park and let it hit the rev limit over and over again. It will probably hit the rev limit once or twice and then start to bog down.