I have a '91 GTA w/305tpi. Have a different cam. Since the cam, it has idled rough, and rich too!!
Have checked the iac and cleaned it, checked and no vac leaks. Put it on the scanner and found out something. The idle only gets erratic when the scanner shows that it goes from closed to open loop for a brief momentg?? What does that mean? Do I need a new ecm?

Anything else to check? I have the egr disconnected, would that do it?

Any help would be appreciated!!!

LB9GTA

 

Your speed density system might not like the new cam all that well... I don't have first-hand experience with an SD system, but I do know that it's less tolerable to engine changes unless the chip is tweaked a little bit.

You may want to check your TPS voltage to ensure that it's set at 0.54 volts at idle. There's an article in the Tech section that explains how to do it.

Also, about that EGR... guys here run without EGR and specifically set up their computer to run without it. That's usually alright. I saw a set of heads, from a stock vehicle with a nonfunctional EGR, that literally swallowed the exhaust valves because they got so hot -- the heads were devoid of any sort of valve seat. That may have been an extreme case, but it's enough to make me keep my EGR. I doubt that's causing a poor idle, but it's something to consider. Search the forums for other opinions on the subject, too.

 

Checked and set the TPS and it is fine.
I will try to hook the egr back up and see if it makes a difference.

Anyone else?

LB9GTA

 

What cam is in the engine?

 

Comp cam - 206/212.
.487 lift and can't remember the rest.

LB9GTA

 

Anyone have the problem with going from closed loop to open loop???!??