I have a 1991 GXL NA
It runs and drives strong, however even after it is warmed up, the idle still oscilates from 250-1000 RPM's. Whenever it gets down really low, the check engine light comes on. But as soon as i give it gas the check engine light goes off. And then sometimes randomly when i am driving in normal RPM's the check engine light with flicker for no reason. As far as the idle goes, i messed with that screw on top of my intake and it didn't help much. I have already searched the forum for threads on setting idle but couldn't find anything. If anyone as any help as how to smooth out my idle, and fix the flickering check engine light, i would appreciate it.
OH, i also have already run a bunch of ground wires from battery to frame to primary coils and secondary coils to fuel rail, to intake to pressor sensor and to ECU.
I need all the help i can get!
Thanks

 

Being it's a '91 I would start by pulling any error codes stored in the ecu. That can be done by grounding set engine coupler by battery and reading the engine light responses. I know quick summary, but don't have thread handy at present.
As far a idle, many reasons. Check for vacuum leaks by spraying starting fluid, carb cleaner, etc on vacuum lines. Check tps for proper function and correct setting, then the dreaded bac valve which can cause monumental problems. Make certain to check the inner seal of the bac to be sure it's not leaking.
At least it's a starting point.

 

But if my ECU had codes stored in it, wouldn't the check engine light be on all the time, instead of flickering on and off???

And how do i check the BAC?

 

Also, when setting the idle, is it simply a matter of turning the screw on top of the intake, or do you have to jumper the battery and then turn the screw?

 

bump^

 

The engine light will flicker on and off. Not on all the time. The idle should be adjusted by the bac screw if possible before adjusting the throttle plates.
Rather then tie up the thread with info that's been posted before, I'll send a PM later tonight if needed. Must leave work now as I have an appintment.

 

check your bac valve and make sure its clean, check for exhaust leaks and make sure your TPS is set right. i had the same problem because my bac was all dirty. i cleaned it and set my tps and now i have a soild idle at 800rpms

 

where can i find information about setting my tps?
I just bought a tps from someone else off the forum, and just slapped it in my car. How do you set it?
Any tips on the process of cleaning the BAC?

 

where can i find information about setting my tps?
I just bought a tps from someone else off the forum, and just slapped it in my car. How do you set it?
Any tips on the process of cleaning the BAC?

Just out of curiousity, where in Lancaster do you live Russ?

 

take off the bacand swap some carborator cleaner in there. thats what i did. your manual you show you the proper way to set the TPS. i live near strasburg, where abouts are you?

 

Thanks for the help, i will see what i can do.
Also, for some wierd reason yesterday after stopping at the bank, my car wouldn't start up again. So i had someone jump me, and after a bit it started. I am wondering If that is a sign of a bad alternator?!?!?!

I am about an hour from you. I live in Mechanicsburg which is just south of Harrisburg.

 

NO!!! some codes dont even turn the light on to begin with