Question for all the mechanics out there...

[Snowdancer]

Here's a quick rundown of my vehicle and the problems it's having. I will gladly answer any questions to the best of my ability, which admittedly is limited or else I'd have fixed the dang car. I am really hoping you all can shed some light on what could be wrong; otherwise I'm going to have to salvage this car and buy another which isn't my first choice but I really need a reliable vehicle.

1990 Chevy Lumina Euro 3.1ltr
130,200 actual miles
New Computer in 2001
New Starter in 2002
New alternator 20 mos ago
New Platinum 750 battery 2 mos ago and only 34 miles put on new battery.
Transmission checked and tranny filter changed/replaced in 2003
Regular oil changes and tune ups as recommended in manual.

I don't go running around too much and in Jan the battery died, I had AAA do a jump start and all was ok until the car sat for a few days again and then it was dead and needed another jump start. Ok, AAA guy says the battery is probably old( it was an Interstate bought in 1999) and needs to be replaced.
Since having it installed, the car has died whenever it decelerates to below 20mph or when I apply the brakes. It's like instead of stopping at an idle level it just keeps going down until it dies.
I've had it looked at by two reputable mechanics and both said the diagnostics 'say' it is running just fine and neither could figure out what could be the problem. Not only did they do the electronic diagnostics but a visual inspection and they tore into the engine/lines to check filters, hoses, fuses, etc. They did agree with me, it is dying-they just don't know why.
Oh, this has everyone baffled- for the first 10 min or so until the engine warms up-it doesn't die when I slow down or stop-it only happens after the engine is warm.
It is Not overheating and I did check all of my fluids including the radiator just to be sure and not trust the guages alone. I wondered if the computer could be going out again but I have no way of checking and the plug in diagnostics seem to say the car is running just fine.


Do you have any ideas what I could have going on here or do you think it's just time to let the old gal go to the big parking lot in the sky??
Thanks for your patience and I hope I explained things well enough.

[DrippingSprings]

is the ac running when this happens? does it happen with it and when its off also?

could be more than one possibility. could be a tps throttle position sensor etc.

Find someone with a good scanner not one of the el cheapos. something like snap on with troubleshooter etc. Mine will test for problems,flag it then offer the option of testing said component while still on the car. one of the 15 dollar jobs wont do this. It costs about 50 bucks usually to get it checked with one.

dont fall for a parts changer find a real mechanic. Every sensor etc on the car can be tested with the right equipment before replacing. alot of folks just start changing parts at your cost til they get lucky and find the right one. I have a kit with a vacuum pump digital meter etc etc that will let you know if that part is really bad before you actually pony up and buy a replacement.

i wish you were closer id check it for you for free.

[agmantoo]

Engines that die when the brakes are applied typically have a vacuum leak.
This is a fuel injected engine isn't it? You need to have someone to check the throttle position sensor with a multimeter and have them to check the oxygen sensor.
PS...When was the last time you changed the fuel fliter?

[georger]

The Chev 3.1 is basically a 2.8 with an attitude.

I had an 88 Eurosport witht the 2.8 that did the exact same thing as you describe.

It was the EGR valve, it sprung a vacuum leak.

[raymilosh]

i think the dead battery problem and the car stalling problem are unrelated.

Something is using electricity when the car is not running and it uses it all up in a few days. It is likely something like the light under the hood or in the trunk is not turning off. Look for something obvious. If you can't find it, it may take a mechanic a while to track it down. A good test would be to make sure the battery is charged (like after driving it), then disconnect the battery terminals and let it sit for a few days. then reconect them and try to start the car. If it starts, then you can be sure that the battery is still good and that something has been using the electricity up.

About the car stalling...it does dound like it has developed a vacuum leak. The computer runs a mixture rich in fuel while the engine is warming without much regard for what's coming out the tailpipe, when the engine warms up, the computer checks on the O2 sensor and begins to alter the fuel mixture. A vacuum leak causes the mixture to be too lean (not have enough gasoline in it) and the engine will stall. The computer doesn't have a sensor that can detect a vacuum leak, so it can't tell that anything is wrong with the engine.

You said the engine began stalling after the battery was replaced. That's prolly an important thing to keep in mind. I'm thinking that it is likely that the person who installed the battery inadvertantly did something that makes the car stall. My guess is that he or she pulled a vacuum line off or broke something that has to do with vacuum. I'd suggest checking all vacuum lines that run near the battery or listen for a hissing in that area while the engine is running.
Even though these 2 problems are baffling, their solutions are probably pretty simple. Usually the computer and the sensors are NOT the problem. Usually it's something simple. It's just a matter of finding a mechanic who is willing to ask you questions and figure out what is wrong by diagnosing it instead of just guessing and changing parts. good luck.

[Snowdancer]

Thanks guys, I'm going to take it to an older gentleman who has a fairly large shop. He is a good mechanic-not a parts changer; I hadn't used him for this since he's not as close as the others(18 miles away) and I will have to get the car towed since I'd need to get on I40 to get to his place. Not something want to do with a car that keeps dying.
But armed with some suggested items/parts for him to check-it's worth the effort and tow.
Maybe I can get another few years out of the old girl after all.

[ericjeeper]

You say it dies.. does it restart right away? If it does it is a great chance it is the CPS Crank position sensor. Not an overly expensive part nor hard to change

[georger]

It's funny there was a mention about the stalling problem beginning after the battery was changed.....

On that old chevy of mine, I changed the battery the evening before - my dad dropped off a seldom used battery for me to install.

The battery is a million miles from the EGR valve.

Yet the next morning when I drove to work, the engine stalled as I decelerated to a stop light. This problem persisted and it turned out that the EGR valve developed (or already had but grew worse??) a vacuum leak that was screwing up the idle mix.

Quick test - disconnect and plug the vacuum line(s) going to the EGR valve, see if the leak is in the diaphgram. Drive the car this way and see if the stalling problem is eliminated.

Also another test, this with the engine cool and off.

You can remove the vacuum line(s) from the EGR valve. Reach with your fingers and depress the diaphgram.

It should move in with some resistance. Then plug the vacuum port(s) with your fingers.

Let go of the diaphgram but keep your fingers near it to feel if it moves significantly while you're holding the vacuum port(s) plugged with your fingers.

If it starts to move back out significantly, you definitely have a vacuum leak.

But if it more or less stays put over 60 seconds, the diaphgram and any seals are still ok.

You could still have a vacuum leak if the EGR valve isn't closing properly (carbon build-up), that would require removing the valve and cleaning any carbon out from where the EGR valve mounts to the engine.

[Snowdancer]

Originally Posted by ericjeeper

You say it dies.. does it restart right away? If it does it is a great chance it is the CPS Crank position sensor. Not an overly expensive part nor hard to change

Eric, yes it starts right back up. Now if I don't give it gas upon restarting-after it's warm and is doing the stalling, it will stall right away again.
So luckily, it's an automatic so I can have one foot on the accelerator as I'm restarting the darn thing.
It really is quite a game of agility.

[fixer1958]

Does it stall as soon as you put it in gear and run ok in neutral?
If that is the case it may be a torque converter clutch that is hanging up. That year was prime for that.
If it acts as the above, there is a square plug on the front side of the tranny with I think 4 wires. Shut it off and unplug it and try it. I won't damage anything. If it's ok then, leave it unplugged. You may get a check engine light and loose some gas mileage but other than that it will be fine.
If that is the problem I don't know what it would have to do with the battery.

It could also be the EGR as other posters have stated, but that wouldn't be just a warm problem because it's not vaccum controlled. If there was a chunk of carbon it would act up most of the time on startup. Take it off and look. You will be able to see it in the orfice.

Just trying to help.

[clovis]

I just sent you a PM, KY Guest.
clove

[rambler]

You do have a vacumn leak.

On my different brand machine, they built the throttle a bit thin & weak. Over time, age, & heat cycles, the thin parts warp & when the engine gets hot, a gap develops letting air in.

Just another possibility, when the pros don't find normal issues - can be an air leak coming in past mating surfaces that don't mate right when the engine gets warm.

--->Paul

[Beeman]

Your vehicle has a system which requires an idle relearn after any interruption of power to the computer. The easy way to do this requires a diagnostic scan tool with the capabilities like a Tech 1.
from memory here's the other way.
turn everything off in the car including A/C and all accessories.
Disconnect battery for a minute or 2
Start car without touching throttle or anything else and let it idle, if the car starts and dies you might have to disconnect battery again.
Let car idle until the cooling fans cycle on and then off.
Shut car off and restart, idle learn should be complete and car should behave.


Again from memory there is a new program (prom) for your computer which eliminates this strategy. This should have been done on computer replacement if the tech knew about it, but unfortunately most don't. They just reinstall the factory prom from the old computer and never check for updates.


For anyone's general knowledge disconnecting the battery on a late model car should include keeping the memory alive while battery is disconnected. A simple 9v square duracell battery hooked to the cigarette lighter with an adapter will keep all memory alive in the vehicle including radio presets and any other programmed items that will be lost. This became a standard procedure for most vehicles quite a few years ago.