SES Insanity!

[1999blackprixgt]

Hey guys, new to the forums. Have many issues but need help with one particular problem, going crazy! First a little background....I have a 1999 GP GT two door with a 3800 series II and 117,000 miles. I have already replaced starter, crank positioning sensor, MAF sensor, AC Delco plugs\wires, intake plenum, and MAP sensor. That all was done within two weeks, imagine that! Now to my first issue...

Last weekend I went to turn left and accelerate up to 35 mph but instead the car started hesitating and sputtering, would barely accelerate. The RPM's were jumping around and the SES light came on and started blinking. When I pulled it over and placed the car in neutral and then in park and rev the engine I had no problems or misses. Only when I'm driving. So I went to an autoparts store and had the OBDII read the code. Unfortunately I'm an idiot and didn't ask for the code but it displayed cylinder 4 misfire. I checked the plug, wires and then tested the coil which came out fine. I ran injector cleaner and didn't notice any results. What else could this be?! Should I take it to the dealership and have them "try" and diagnose the problem ($85)??

Sorry for the novel, desperately need help. I also have questions regarding 4T65E tranny and suspension. Will post them next time. Thanks guys.

[troy1]

Do you know if the crankshaft variation learn was done when the crank position sensor was replaced?

[1999blackprixgt]

No, I had to take it to a shop and have them install it. I didn't have the right tool to remove it and had to get to work. That happened sometime in March though. Would that take affect now after all this time and cause my problem? Just asking, I obviously don't know.

[BNaylor]

All the crank variation learn (case learn) does is allows the PCM module to discriminate between real and false misfires. In other words prevents false misfires but with false misfires you will have no driveability issues like you are experiencing. Too much of a time lapse and I doubt your issue is a case learn.

How did you check the coils? With a meter (DMM) - primary and secondary resistance or swap them out with one another? Also, have you run a fuel pressure test.

[1999blackprixgt]

I actually had a buddy of mine who has his own garage temporarily swap the coils in which he found no difference in performance. He did mention however the coil modulator. He thought there might be an arc which is causing cyclinder 4 to misfire. I heard that can be pretty pricey to replace.
I have not done a fuel pressure test yet, how do I do that? Can I do that myself?? If so, what should I look for?

Sorry guys, never really had to do much work on cars aside from tune-ups and brakes. Bear with me. Thanks.

[BNaylor]

We're assuming the DTC is a P0304 which is a fixed cylinder # 4 misfire. Coil modulator? Probably referring to the Ignition Control Module (ICM) which is possible.

To check fuel pressure all you need is an automotive type fuel pressure tester that you connect to the Schrader valve located at the area of the fuel pressure regulator on a NA SII 3800 engine. See pic below.

Specs will be around 48-55 psi at fuel pump prime (ignition to ON not START). Next check will be with engine running. Readings will be different or vary at idle and with vacuum line on or off the fuel pressure regulator.

What type AC Delco spark plugs are you using and number/heat range. What brand ignition wires or Delco type?

[tblake]

I would pull that plug out and have another closer look at it. There have been a lot of members who have reported cracked delco 41-101's