87 GN wont idle stumbles

[Roger S]

Have replaced coil packs, MAF sensor ect. Any ideas ? Thanks

 

[Chuck Leeper]

Fuel psi?
Batt volts?
Grounds?
Wiring connections verified?
Scanmaster readings?
Vac leaks?

 

[Firechaser]

It certainly could be all the above, if your running with the original vac lines i would have a hard look at them. They crack/deteriorate and can hide themselves quite well....and the vacuum blocks like to leak too. vacuum leaks will promote terrible idle quality. Does it stumble only when cold or all the time?

 

[dennisL]

Don't forget the IAC, its sole purpose is to regulate idle rpm. Like most, I can't troubleshoot poor idle without data. The sensor data during warm-up and at hot idle will either point to the problem or help eliminate sources.

Which chip are you using?

 

[Roger S]

Not running a chip, all stock with exception of cold air intake. Had the vacume lines gone through and replaced not long ago. Taking to the shop Mon to check fuel pressure ect. Poss TPS ? Ran great all summer just started stumbling on a normal cruise around. Have black residue from exhaust on garage floor so seems like a rich fuel situation to me but will get hooked up and start with the basics. Thanks for the help everyone. Have only owned the car 8 months so still learning.

 

[TurboBuRick]

Try unplugging the maf and see how it runs.

You may also have a stuck injector.

RL