Need some car help

[Melvang]

Alright guys, I am having a bit of an issue with my car.  It is an 03 Buick Park Avenue with the NA 3.8 V6.  It will stall at an idle on occasion, idle RPM fluctates, sometimes get a bit of a surge/chugg at highway speeds shortly after getting in the car, or when cresting a hill to a quick down hill.

The car is not giving any trouble codes either with an OBD II scanner.  Here is a list of stuff I have replaced, checked, or cleaned.

MAF sensor cleaned
Idle air control valve cleaned
PCV valve cleaned
Spark plugs and wires changed
external fuel filter changed
resistance check on all injectors
Bought a new coil pack and swapped it in with each one, no change
intake temp sensor cleaned
3 cans of sea foam
dropped tranny pan and changed filter, when filling back up I added a bottle of Lucas Oil Transmission Fluid Conditioner
Fuel pressure checked out normal

The goofy part is I am NOT getting any trouble codes to point me in the right direction.  This is why I have not looked into crankshaft position, throttle position, or any other of numerous sensors.  The car will die without regard to what gear the transmission is in, A/C on or off, other electrical load items on or off, engine hot or cold.  If I hit the throttle to pull the RPM up over 1k, the RPM still fluctuates but doesn't die.  Sometimes it will catch itself at around 200 rpm and then shoot up to 1,200-1,500 rpm.

Any thoughts on what to check?  I don't have a lot of disposable income to just throw parts at it.

[smknjoe]

Sounds like a timing/firing issue. I haven't had much luck with generic OBD2 readers either. Do they make diagnostic/tuning software for those cars that's reasonably priced? Something like this: http://www.ross-tech.com/

Do the rpms only fluctuate, or does it run "rough" sometimes too...like it's misfiring?

[saturnotaku]

I don't have any troubleshooting ideas, but my family had two GM cars from 1989-1992 with that exact engine. Both suffered from similar problems as yourswhen they reached about 140,000 miles. Not wanting to sink any more money into them, we ended up getting new cars.

[fohat.digs]

I don't have any troubleshooting ideas, but my family had two GM cars from 1989-1992 with that exact engine. Both suffered from similar problems as yourswhen they reached about 140,000 miles. Not wanting to sink any more money into them, we ended up getting new cars.

I had a mid-late-1990s Park Avenue with a lot of miles (>200K) from my father-in-law but he had maintained it well and it was mostly highway miles. I never had any of those problems but the transmission eventually gave out on it.

[Melvang]

Sounds like a timing/firing issue. I haven't had much luck with generic OBD2 readers either. Do they make diagnostic/tuning software for those cars that's reasonably priced? Something like this: http://www.ross-tech.com/

Do the rpms only fluctuate, or does it run "rough" sometimes too...like it's misfiring?

Does not run rough, missfire, choke, cough, sputter.  Just smooth fluctuations, then falls on its face and dies.

I don't have any troubleshooting ideas, but my family had two GM cars from 1989-1992 with that exact engine. Both suffered from similar problems as yourswhen they reached about 140,000 miles. Not wanting to sink any more money into them, we ended up getting new cars.

This is my second car with this motor.  First one I drove to 227k miles.  My dad had an Olds with the same motor that he drove to 300k miles.

[smknjoe]

Maybe it's a throttle control issue then.

[tjcaustin]

Do you have a scan tool that can sample at 500 or less ms?  That may help you narrow down the issue more than anything else.

Also, check compression in all the cylinders and even catalytic converter pressure before and after.  Oh, and there's a tsb on the fuel pressure regulator, check that out, too.

[tp4tissue]

I had similar issue, not fhe same car.  But for me, it was the coil in the air intake valve.

It's that active valve that responds to how much air the engine wants..  there's like a coil on it that was burnt out and not moving smoothly.


The valve itself wasn't dirty,,  it was the coil in the valve.