Hi we have a 99 Z34 3.8 with 181,000 and every once in a while it will chug and have a lumpy sounding idle, I have checked the FPR and its not leaking. it has about 15 inches of vacuum at idle, no trouble codes. I'm going to change the fuel filter just because we have put 25,000ish miles on it in a year and it looks to be original. If anybody has any ideas could you let me know.
Thanks

 

Choo Choo, not a clue. Welcome to forum. I bet someone knows what to do.

 

There could be a ton of things wrong, could be the MAF sensor / IAC valve though.

 

I agree with chibiblacksheep on the MAF but IAC will usually cause bad running at idle constantly or won't idle conditions. i have also seen the crank sensor do that without setting codes until it is completely toast.

 

freeking sweet i have had to replace those before, tons of fun

 

befor changing sensors have a shop do a test on the computer to see if there is a error some where with one or more sensors it is hard to tell. it also could be that cat. check if there is any errors stored in the computer. it will give you a heads up on what needs to be fixed acuatly

 

didn't even think of that, it did have the egr tube rot out and burn a crap load of antifreeze nursing it home

 

I obviously agree proper testing is the only way to fix a car the parts dart board is no way to fix something. So have it checked before replacing any sensors. Did changing the filter help or are you still having troubles? also check fuel pressure and volume output from the fuel pump.

 

changed filter today helped a little have about 41.5-42 psi now had about 38.5-39 psi before did it again but not as bad, going to clean the intake and MAF to see if that helps, i have the stuff to clean both(accual MAF cleaner and intake cleaner) and the fuel filter was only $3 plus it had an AC Delco filter and its got 182,000 miles on it. I'm guessing it was original.