96 Olds Cutlass Supreme problems

[StiKs]

96 Olds Cutlass Supreme 3.1 approx 50,000 miles.

Having a problem with this car where when you start it most times in the mornings after sitting all night. It starts and has a rough idle, sometimes a jerky feel to it, and backing out of the driveway in reverse and as soon as you go forward it kind of hesitates then smooths out in a few seconds.

I've had a problem with it not starting twice now and I would assume whatever is causing the above problem is the same issue here. After letting it sit for a bit or giving it gas while starting it fires up then I get the jerky rough idling for a few seconds then smooths out again.

Sometimes the check engine light comes on and a test at autozone always shows a code for the o2 sensor.

I've had this car in the shop twice, once for a complete diagnostic test where I told him about the light coming on and what the test at autozone said. He tested the fuel pump and said it was fine and same for the o2 sensor and other things and everything checked out fine. The only advice he gave me was that the intake manifold gasket had a slow leak and he couldn't tell if it was getting inside or not. He also said that a o2 sensor doesn't go bad then all the sudden is good again, like he said after testing it. He said it did show the o2 error in the computer's history. He said he wouldn't replace the gasket but refered me to someone. This mechanic could't explain the rough start, etc.

This other mechanic which replaced the gasket's for me kept the car for a few days and drove it around to see if he could get the same problems I am having rough start, etc. Never happened to him either. The next day it started again. The leak wasn't getting inside.

This issue doesn't happen everyday but often enough that it needs attention. I don't know what it could be and I can't afford to keep it in the shop if they don't know what's wrong either.

Any ideas? Thanks

[maxwedge]

Many things can cause this, my 97 Lumina did the same thing for years. I would check the vacuum hose on the fuel press. regulator for signs of fuel , also an injector leaking down can cause this, for starters try a 20 oz bottle of Chevron Techron injector cleaner.

[StiKs]

Thanks for the reply. I did forget to mention the plugs were changed and had the original plugs still in it. The wires were not replaced.

I did put some STP Complete the most expensive one at Walmart about 1 month ago it doesn't seem to help should I go ahead and get this chevron treatment you mentioned and is it better than the STP?

[maxwedge]

Techron is what GM sells for injector cleaning, repackaged with their label, this is still experimental.

[StiKs]

OK, is it safe to go ahead and try that even after just putting a bottle of STP in it just over a month ago?

If that STP didn't help it then is the Chevron that much better and going to maybe fix it?

[Cutlass_kid]

Originally Posted by maxwedge

Techron is what GM sells for injector cleaning, repackaged with their label, this is still experimental.

Speaking of techron. go to chevron. they have that stuff in thier fuel.

[StiKs]

I put some of that techron in it but after driving it two miles and shutting it off at the doctors office it wouldn't start after getting out of the doctor's office.

Early yesterday morning I put a new fuel filter on it thinking maybe it was getting blocked somewhere in there. After changing the filter and starting it, it started very rough and I rev'd up the engine to get it to smooth out. At this time the check engine light started to flash then went solid after several flashes.

So after this I took it to autozone and the light showed a p0300 code misfire, so I had them reset the light thinking it was caused by the way it started after putting the filter in. Leaving autozone I went to O'reileys and got that techron and filled the tank with it and headed to the doctors office.

When I left the doctor's office it started rough and it didn't matter how much I tried to rev it up you couldn't actually here the engine rev but the gauge would move a little, eventually the engine choked and died. After about an hour of trying to get it started it finally started as I was giving it gas as it was trying to choke and die. When it finally started to smooth out I got a couple backfires and a smell and I took it home.

I talked to the two mechanics that looked at this as mentioned earlier in this thread. They want me to bring it back in to have it looked at, but I told them it doesn't do this constantly and that it probably wouldn't do it while they had it like last time it didn't. So I can't afford to do that. I had the gaskets replaced and the spark plugs, wires are still the originals. Doing this didn't fix the root problem.

So I talked to a guy at O'reiley's and he said he thinks it could be a few things. Either a cam sensor, a crank sensor or the ignition coil and ignition module.

What do you think?

Please help.