1992 seville runs poor cold.

[67johnny]

Hi All.

First post here.

Just bought a 92 seville and the darn thing runs like a bag of s**t till it goes into closed loop mode (super rich).

Things I have tried are: map sensor, coolant temp sensor and pluged and checked the EGR !

A local caddy guy said it was the intake gaskets as it runs real rich so I changed them out with no change in runability.

I can completly plug the throttle body air intake off and it still runs.

Where is it getting extra air from. Sprayed it down with brake clean looking for vacuum leaks and found none.

Any ideas will be appreciated as I am stumped here.

Thanks all! Johnny.

[WinoBot_Beta]

Does this vehicle use the THERMAC system whihc uses a damper in the air intake to divert and breath warm air off the exhaust manifold when cold and then when warm it opens and breathes in cool air?

I am unfamiliar with the 4.9L but if this is the case, then perhaps that damper is remaining shut.

I had similar symptoms when I used to drive my 86 Deville and a new valve was the cure.

[Ranger]

Does this vehicle use the THERMAC system whihc uses a damper in the air intake to divert and breath warm air off the exhaust manifold when cold and then when warm it opens and breathes in cool air?

I am unfamiliar with the 4.9L but if this is the case, then perhaps that damper is remaining shut.

I had similar symptoms when I used to drive my 86 Deville and a new valve was the cure.

No it doesn't. The fuel mixture is controlled by the PCM.

Check for a leaky FPR. It's the small canister on the fuel rail. Pull the vacuum hose at idle. If any fuel leaks from the nipple, it needs to be replaced. Also pull the DTC's.

[67johnny]

Thanks for the replies.

I did check the fuel pressure reg and it is not leaking and does bump the fuel pressure when vacuum is removed.

The odd thing is how rich it goes in open loop . The O2 sensors are functioning well and read about 800 when cold !

The injectors must be almost flat out.

As soon as we go closed loop it seems to be OK with a good number of cross counts.

Any other suggestions?

Thanks, johnny.

[bobbnsueb@sbcglobal.net]

Hi

My 91 STS had the exact issue.

After fiddling around, I gave up and took it to a good dealer.

They assigned it to the best old timer who knows the 4.9.

But he would think he fixed it then after cooling off all day or all night, he would find it still failed.

He even replaced the computer.

Thought it was fixed eventually and said so.

They only charged the original $100 or so. I don;t remember the exact amount.

When I got it home again, something triggered the thought about grounds.

I had already cleaned the ground near the starter nut no help.

SO I took my jumper cables on the battery negative post and clipped one on the engine and also one on the body.

WOW it ran great!

So I removed the one to the body leaving the one on the block. Still ran great,

I added a fairly heavy wire from a bolt at the engine brackets to a screw behind the battery.

There are a number of grounds right there from most of the systems and circuits.

This was a good fix and it is still running great cold or hot a year or more later.

I then removed all the grounds and cleaned them for good measure, but left the new wire on there.

Good luck,

Bob B

[Texas Jim]

Hi

My 91 STS had the exact issue.

After fiddling around, I gave up and took it to a good dealer.

They assigned it to the best old timer who knows the 4.9.

But he would think he fixed it then after cooling off all day or all night, he would find it still failed.

He even replaced the computer.

Thought it was fixed eventually and said so.

They only charged the original $100 or so. I don;t remember the exact amount.

When I got it home again, something triggered the thought about grounds.

I had already cleaned the ground near the starter nut no help.

SO I took my jumper cables on the battery negative post and clipped one on the engine and also one on the body.

WOW it ran great!

So I removed the one to the body leaving the one on the block. Still ran great,

I added a fairly heavy wire from a bolt at the engine brackets to a screw behind the battery.

There are a number of grounds right there from most of the systems and circuits.

This was a good fix and it is still running great cold or hot a year or more later.

I then removed all the grounds and cleaned them for good measure, but left the new wire on there.

Good luck,

Bob B

Bob B,

Thanks for that info.

It may very well help some a lot who has this problem.

[67johnny]

Thanks Bob!

Will try this tommorow!

Johnny

[KHE]

I seem to recall a ground wire near the starter that corrodes. Try cleaning that ground connection also.

[67johnny]

Hey All.

Tryed a new set of auxillary ground cables and nothing changed .

Any other ideas?

Thanks, Johnny.

[CoupeDTS]

Hey All.

Tryed a new set of auxillary ground cables and nothing changed .

Any other ideas?

Thanks, Johnny.

800 reading for o2 sensors? Is that normal for that car? Im thinking of other cars that 160 or numbers around that are normal.

[KHE]

You cleaned the ground by the starter and it made no difference correct? The next thing to check is the connector on the distributor pickup coil - many times, with the age of the car, the contacts will get corrosion and not make good contact. That will cause all sorts of drivability issues.

[67johnny]

You cleaned the ground by the starter and it made no difference correct? The next thing to check is the connector on the distributor pickup coil - many times, with the age of the car, the contacts will get corrosion and not make good contact. That will cause all sorts of drivability issues.

Thanks for the reply.

I did the ground and cleaned all the distributor connections when I had distributor out to do the intake gaskets.

Any other thoughts? Could a bad fuel injector cause the injector drivers in ECM to over-heat etc... ?

Thanks, johnny

[KHE]

Did the problem exist prior to replacing the intake gaskets or did it occur after replacing the intake gaskets?

[67johnny]

Did the problem exist prior to replacing the intake gaskets or did it occur after replacing the intake gaskets?

Problem was present before I changed the gaskets.

It was suggested to me that the intake gaskets were leaking causing an issue.

Thanks, Johnny

[bobbnsueb@sbcglobal.net]

You cleaned the ground by the starter and it made no difference correct? The next thing to check is the connector on the distributor pickup coil - many times, with the age of the car, the contacts will get corrosion and not make good contact. That will cause all sorts of drivability issues.

OK don't forget the other end of the starter area ground cable,

On our 91 STS a lot of ground wires go to the body behind and in front of the battery.

I removed the screws and shined up the terminals there also.

Bob B

[BodybyFisher]

Check the ignition wires, they may be susceptible to morning moisture on them and they cross talk or short to ground until the engine is warmed up and the moisture is dried up.

Have you check the engine for misfires. I don't believe that the OBD1 system sets a misfire code you will need a real time monitor to monitor misfires

I would also monitor O2 sensor data

I would also swap in a KNOWN GOOD PCM/ECM

I would check the COIL, it may not fire consistently when cold

I would swap in a known good ignition module and pickup if equipped

I would check the plugs for carbon tracking on the porcelain, that occurs at a specific moisture level

I would change the fuel pressure regulator, if you have not done so, at the very least I would check the fuel pressure under all circumstances and check the fuel pump operation

[67johnny]

Thanks, will try that today!

Check the ignition wires, they may be susceptible to morning moisture on them and they cross talk or short to ground until the engine is warmed up and the moisture is dried up.

Have you check the engine for misfires. I don't believe that the OBD1 system sets a misfire code you will need a real time monitor to monitor misfires

I would also monitor O2 sensor data

I would also swap in a KNOWN GOOD PCM/ECM

I would check the COIL, it may not fire consistently when cold

I would swap in a known good ignition module and pickup if equipped

I would check the plugs for carbon tracking on the porcelain, that occurs at a specific moisture level

I would change the fuel pressure regulator, if you have not done so, at the very least I would check the fuel pressure under all circumstances and check the fuel pump operation

[67johnny]

Just a quick update here.

Tryed a new module yesterday with no change and the 02 readings on start-up "cold", hover at 780 to 800 (rich) on front and rear banks.

As soon as it goes into closed loop and the 02 sensors take over the fuel control for the engine, all runs fine.

Will look at wire today if I get a chance.

Thanks all.

Thanks, will try that today!

Check the ignition wires, they may be susceptible to morning moisture on them and they cross talk or short to ground until the engine is warmed up and the moisture is dried up.

Have you check the engine for misfires. I don't believe that the OBD1 system sets a misfire code you will need a real time monitor to monitor misfires

I would also monitor O2 sensor data

I would also swap in a KNOWN GOOD PCM/ECM

I would check the COIL, it may not fire consistently when cold

I would swap in a known good ignition module and pickup if equipped

I would check the plugs for carbon tracking on the porcelain, that occurs at a specific moisture level

I would change the fuel pressure regulator, if you have not done so, at the very least I would check the fuel pressure under all circumstances and check the fuel pump operation

[67johnny]

Hey All.

After a two week search of all the boneyards around here i have had no luck locating another 92 seville to get an ECM out of.

Does anyone know what other years may interchange for me? Any companys that can check them for issues?

Thanks, johnny

[BodybyFisher]

Rockauto.com has an AC DELCO reman for $132, and we have a 5% discount coupon someplace here

[67johnny]

Thanks, Will try rockauto tomorrow.