Hey guys this is my first post here on the site. I'm having some problems with my engine idling too fast.

To start with the car is an 84 Trans Am with the L69 motor, a 700R4 trans, and the computer controlled Quadrajet. Within the last few weeks the engine has been idling way to fast at around 1500-2000 rpm when warmed up and in neutral. The other day I tried readjusting the timing and then setting the idle speed. That seemed to work at first. I got the motor to idle at about 700 rpm in drive, and after a test drive around the neighborhood it seemed like I had fixed the problem. But the next time I drove the car it was idling too fast again.

When I start the car up idle is a little fast at around 1000 rpm in drive, but it never drops as the car warms up. In fact it raises. After a few minutes of driving the idle won't go below 1200 rpm in drive. And when I finish driving around and put the car in park, the idle climbs to almost 2000 rpm. Visual inspection shows that the throttle arm won't rest on the idle set screw. I tried pushing on the arm to get it to touch the screw, which drops the rpm's a little but not enough, and the arm won't stay there. There's a lot of resistance in the arm but nothing seems to be pulling on it. All the cable linkages have enough slack, it just won't rest on the set screw.

Any ideas? I'm really at a loss here. And sorry but replacing the carb with a non computer controlled one is not an option at this time. If I had the money I would.

 

Welcome aboard.

Sounds like the high idle cam for the choke isn't dropping off all the way. Typically when that happens either the choke thermostat isn't opening the choke all the way, or the linkages are gummed up.

1st thing I'd check is the power going to the choke thermostat. Should be 12v with the ignition on and the engine running. If that checks out, check the resistance of the choke thermostat. If open, you need a new choke thermostat.

 

I have an 86' TA 305 5spd, with the same issues....It started idling at around 1200-1500rpms....I went through buying a rebuilt carb--don't go there....it's more problems than it is worth, trust me. I just bought a carb that belonged on an automatic-same year and motor though. It seems to be running pretty good, except I noticed she still wants to idle a little high, once she warms up. So I'm looking for an answer as well, if I find one I will let you know....

 

Thanks for the insight, I'll have to check that out. Just wish I had brought the multimeter with me to school this quarter.

 

Spray the carb linkages with WD-40. It will desolve any gunk and prevent corrosion.