Stumbling when warm?

[jretrodude]

I noticed today the GN stumbled a little bit when driving about 20 mph to 30-35? What could be causing that? Just had the TCC solenoid replaced, MAF sensor has correct numbers, and my cam sensor cap is tightly screwed down? Could it be trans related? The trans shop said when they did the trans filter change that the fluid looked real good and shifted fine? If I get about 40 to 55 runs fine with no stumbling? Boosts up real nice too. I have not changed the coil pack or module could that be a culprit? Scratching my head again. Any help would be greatly appreciated. Thanks. Also seemed to do it after about an hour of driving?

 

[Hacksaw]

First, take the hose off the Throttle body & spray some carb cleaner into the IAC intake while it's running with the throttle slightly open enough to keep it from stalling. IAC's can gum up on any car that has them, & cause stumbling.

Also, has it had the fuel filter replaced lately? Have you used fuel injector cleaner lately? Spark plugs OK?

The TPS could also be flaking out. The best way to see that would be a scan tool. Or, check it with an ohmmeter, engine off through it's travel for any glitches. The resistance should change value smoothly.

 

[jretrodude]

Yep all that done!

Spark plugs have about 3500 miles on them (AC Delco plugs) new wires about 3500 miles on them. Fuel filter last year. Only thing I haven't done is clean the intake holes like you pointed out with the pic. Can the car still run with the elbow off the car? Also IAC readings at idle are like 04 to 15. No malfunction codes and the scanmaster says the TPS is at .42.

 

[Hacksaw]

Yes, it will run without the elbow, though you might get a false MAF error code by doing that, but you can clear that. IAC should be more like 10-25 at idle, but clean it out first, then reset/clear the ECM, then warm it up & recheck the IAC.

Adjust it, if needed, after cleaning & some testing:

http://www.vortexbuicks-etc.com/tuning.htm#IAC (Idle Air Control) Adjustment

That closed TPS reading is fine, but the TPS could have a glitch area that is best seen by checking engine off with an ohmmeter. If you adjust the IAC, the TPS will need checking & possible adjustment.

 

[aminga]

Yes, it will run without the elbow, though you might get a false MAF error code by doing that,

It will run without the elbow if you unplug the MAF. If the MAF is plugged in and reading 0 airflow it won't

 

[jretrodude]

Hmm?

Didn't have any carb cleaner but I used seafoam in the idle air intake hole. I did have to crack the throttle a little bit though to keep it running. I poured some seafoam in there and it backfired LOUD out of the intake hole where the elbow was at and spewed like a white residue out of it? I hope I didn't blow anything like a plug or nothing? Checked the scanmaster readings after I reassembled and it stayed at 25 but went down to 00-09. Still no malfunction codes or anything? Did not reset the computer either. Seems to idle ok with no reving up and down and dying, but did not drive it either or back it up. I did put my pinky in the air inlet hole and it was very black. So hopefully that seafoam cleaned it out? Let me know what you think. Thanks guys!