Ok, this is on my 87 GTA. I previously had a set of SLP runners on the car, and I siamese port matched the plenum. Now I'm strapped for cash and I'm selling the SLP runners and matched plenum. I went and put the stock runners back on, and had to use a spare plenum that I had of my 91 camaro. The problem was that the 91 plenum was not set up for the cold start injector, and the extra little runner from the 87 was sucking in air, major vacuum leak. Anyway, I went ahead and removed the 87 runner and replaced it with one from my 91 to fix the vacuum leak problem. But now the cold start injector is completely bypassed. And now the car will not run. It will not start unless you give it gas, but even after that, it will die if your foot is not constantly on the gas pedal. I let it warm up until the temp gauge was reading 180* and the car had run for several minutes, but it STILL dies if I take my foot off the gas. It ran fine before I took it apart, and I am sure I have no vacuum leaks and all the sensors are plugged in, so I'm thinking it's related to the cold start injector. But it won't even run when the car is warm, without my foot on the gas. What gives? Is the cold start injector really that important? Or is it something else that coincidentally screwed up at the same time? Oh, and I'm not getting any codes at all. Also, I tried running it with the MAF unplugged, that didn't help the situation either.

 

Ok, I did a little more investigation and tinkering. I put a scanner on it, and stuff like the TPS and MAT are reading correctly. I went ahead and adjusted the idle with the little idle screw, but I had to move it WAAY out to get the idle to where the car would run on it's own.

 

I think your problem may be a mismatch between the TB and the plenum...not the CSI.

'89-92 TB's route the IAC passage differently through to the plenum.

 

I bet you're right Mike. I was out driving it around tonight, and I noticed that it really just felt like the IAC was not even moving at all. I especially notice it on startup, the RPM drops right back down to where I have the throttle opened to. As if the IAC wasnt working.