hey everyone i have a 91 GTA 305 just will not idle. new IAC , and CTS checked tps voltage and looks good. interesting thing when i tried doing minimum air adjustment with the IAC un plugged the idle would stiil fluctuate, doesnt make sense as terminals a and b were jumpered also. So i disconnected aldl and plugged in IAC but still no difference. Idle will usally be around 1000 rpm but can and will go up to 2000 or so then either idle stady for a min around 1000 or 800 or completely drop off and stall. since this car is speed density can the vehicle speed sensor affect idle? i have noticed that while the car is moving in neutral it doesnt stall 9/10 times, it is coming to a stop or at a stop it really acts weird. Any ideas appreciated

 

Possible regulator diaphram problem or vacuum leak?

 

Check your timing, and fuel pressure. My 86 IROC uses 6* timing. any Trouble Codes?

 

Vacuum leak at your brake booster?

 

thanks for the replies, well im running about 8* timing initial, fuel pressure is @ 40 # . I went around the entire intake with a bottle of propane on to see if i could find a vaccum leak but didnt find any thing. although i can try it again. the lower intake seal blew around the water passages about 2 months ago so i have all new gaskets top and bottom BUT this all was happening before i replaced the gaskets. although i did find a small crack in the magnetic pickup( i think they call it that ) in the distributor while replacing the ignition module. could that affect it as in spark scatter? WOT it runs good it ran a 14.80 on a HOT night before the lower gasket blew. Any ideas much appreciated again!

 

Let me tell you my experience. When I first got my IROC to turn on after 7 years, it would not rev over 2000 rpms. It would backfire like crazy. So after my investigation, I found that my pickup coil was shattered. So after I replaced the pickup coil, I took her out for a drive and she ran fine.

 

Chevy86 IROCZ is on the right track there. If your pick up coil or magnetic pick up is damaged, that is the cause of your problem and you will need to replace them.

 

thanks for the input and i did find the magnetic pickup in the distributor is cracked and falling apart. A new one from summit should be on my doorstep this afternoon and if it cures the problem ill post it
thanks again

 

Be carefull. You WILL have have to pull out the dizzy. But before you do that, mark (with a permanent marker) the base of the dizzy and the block so that you'll know the position of the dizzy to the block. Then mark the position of the rotor to the dizzy. Take extra caution when you pull out the dizzy because of the oil pump input shaft. Lift straight up without twisting. Now when your ready to pull out the pick up coil, there is a tiny thin round ring that holds then coil in place. Remove it. Oh, I forgot to mention. Spray some degreaser down the shaft of the dizzy because it will be extremely hard to pull it out. When done replacing, drop straight in with the rotor in its correct position with the mark you made. The rotor will twist a little bit because of the teeth on the cam. Good luck bro.

 

ok got the new distributor in fired it up , timed it reset minimum air. It has never run, better rock steady idle couldnt be happier .
Thanks to everyone! never would havve guessed it would have been the that.

 

O so you got a whole new dizzy. Cool bro. Now your set for about 2 decades.