I have an 86 GXL

I've been trying to track down my performance issues for the longest time. One problem i can't resolve is the idle. It idle's at 750rpm's but likes to dip to 500 once in a while... here's what i've done:

1. Jumpered Initial Set Coupler (idle climbs to 850 when this is done)
2. Adjust mixture screw... cannot increase idle at all.. only thing i can do is further decrease idle by making the idle mixture rich.
3. Adjust plenum screw... again, will not increase idle. Only decreases idle if i screw it in far. Also, if i make a quick turn out with the screw, the engine speeds up for a split second, but quickly returns to the initial speed.

4. Adjusted the TPS. Adjusted resistance to 1k. Also checked the set connector and only power at one connector... so that is ok.

5. BAC is fine, although maybe a little slow to respond if brakes, AC, and steering engaged.

I've read about the bolt to adjust idle up, suggested by Hailers, but this seems to be a bandaid just to increase idle...... it looks like there are other factors involved that will not allow me to increase my idle speed......

Im surmising whatever is causing my idle to be low and unadjustable is affecting my performance..... maybe running too rich??

Any suggestions?

Thanks,

Matt

 

anyone?

 

Have you checked your spark plugs no matter how long ago you changed them? I had a probelm just like yours this week and bam 750 idle after change of plugs and i still have stock wires on my car with only 68k on clock

 

plugs are fine and have been replaced within the last 1k miles.

 

Could you elaborate on "likes to dip to 500 once in a while". Do you mean: it drops to 500 then come back up right away (some kind of hunting) or does it drop to 500 and does not come back.

I assume the above is with no electrical load of any kind ??

Hugues -

 

it will drop to around 500 on load..... and then bump back up.... especially if the ac is on.... sometimes when the ac compressor kicks on, it will start to hunt up and down...

 

hmm sorry i have no idea i would look for vacuum line leaks

 

For the AC part,
I would think the BAC might be the culprit. When you turn on AC, the rpm should go up and come back to your usual idle. What happens if you idle with no load and you unplug the BAC ? (rpm should drop a lot. if not BAC or ECU to BAC is no good).

If you turn on head lights or turn on vent to the max (no AC), what happens. The rpms should go down a little and then come back right away to normal idle. If the rpms drop a lot, then it's not normal. I would suspect something is wrong with your charging system: alt or battery, maybe both.

Double check your TPS settings. You should get 1 volt with iginition on and engine pretty hot. An hunting idle is usually due to bad TPS adjustment or vaccum leaks.

Regards,
hugues -