Ok, here's the scenario. I have an 86 305 TPI/700R4. Lately I have been having some troubles with my idle. Here's how it goes.

On cold start the engine starts up, sputters at 300-400rpm for 5 secs and dies. To get it to idle I have to adjust the Minimum air higher, let the engine warm up and then adjust it back to normal. When I do that, and the engine is warm, it begins to idle normally.

Then when I take it out on the road, and give it some gas the engine has power, but when I let go of the gas and stop at a light, it goes into a REAL rough idle and has almost no power until 2500-3000rpm after that. To make the engine run normal again I have to repeat the Minimum air adjustment again, and the same thing happens when I step on the gas again...

Anyways, I think that its my IAC. I took it out and looked at it, and the plastic retainer that holds the spring and stick dead center was broken so the stick and spring had significant travel side to side. I think that when I floor and let off the gas the spring gets stuck somehow (due to being missaligned) and doesn't open the IAC again until I forcefully adjust it with the screw.

BTW Could to cat ot being attached very loosely on both sides cause something like this?

Somebody Please tell me if this sounds like it could be the case or if I am COMPLETELY off. I am close to taking the damn TPI off and replacing it with a non-computer carb!

Thanks for the help,
-Max

 

I had similar problems. Replace the IAC, and be sure to follow the proper instructions for reinstalling it.

------------------
Rob
'86 TA 305 TPI
Gutted MAF, Ported Plenum
TB Bypass, Home made Cold Air Intake,
Edelbrock T.E.S.
48psi regulator, (Nickel method)

 

It would seem as the IAC is not responding, but may be due to plugged passages in the IAC ports in the TB.

Other thing is when you adjust min air, you're changing the TPS voltage as well, which could cause idle issues too.

But I think you're on the right track, would seem that the IAC isn't responding for one reason or another.

Last thing to check is to disconnect the MAF sensor as well, as mine was going bad, I needed to crack the throttle to get it to start..worth a look at.

 

Well the MAF sensor is good, the passages are clean so I guess it must be the IAC. Will replace with my next pay check. Anywasy today I was fooling around with teh Minimum air adjustment again and I brok the head off of the bolt , so now my car idles at 2K rpm. Any ideas on how to get it out, I am going to try drilling it out.

If anybody has any more ideas on what is wrong with my car please respond.

-Max

 

take a pair of thntipped needle ose while the car is off put it on the threaded part of the screw(between throttle lever and screw) and turn it counter clockwise it wiill adjust no big deal you could leave it like that if you wanted i've been doing tthat for a whiile my torx bit broke and am to lazy to get another it wont hhuurt the tthreads if you dont squeeze it too hard