Alright, I had to replace the opti this weekend because I was getting the DTC 36 code, so while I was in there I replaced the IAC and the TPS sensor, and also finished putting OTVC wires on the passenger bank of cylinders. So, crank the car up after doing all of this and first off it was idling at 1500 rpm but eventually dropped back down to 800, so I took it around the block. It is running like crap. It is a constant hesitation. I kept driving for about 10-15 minutes to see if it would "work itself out" and it wouldn't. Once it finally warmed up I gave it a WOT rip and it could barely pass 5000 rpm. So, is this a IAC problem? I know for certain the 5 of the OTVC wires are good to go, because they have been on there for a while, the other 3 I made last night and I would guess they are fine, but I will slap some cheap ones on there just to make sure.

Is there something you are supposed to do when replacing the IAC? Are you supposed to reset it, and if so how do you do that?

I ran it around the block with TTS Datamaster recording for a good 10 minutes so I have plenty of data if anyone wants to take a look. Nothing is flashing up red, but I am not familiar with what the IAC #'s should be. The TPS sensor is where it should be (accept I had to put it up at around 0.9V at idle because it doesn't move the voltage until 0.98 volts). It maxes out around 4.7 volts, so it's should be good. The opti seems fine, it's brand new AC Delco from Jason Cromer. So, all I can think of is the IAC, or perhaps the plug wires, but all in all the car is running like crap.

 

I had a similar problem after replacing the opti in my 94 Formula. 9 times out of 10, problems similar to yours and mine is something small and stupid such as the following most likely candidates;

1. I know it is a royal pain in the a** but pull the opti back off, and make absolute sure it has been properly installed correctly with the tiny notch in the pin alligned correctly. This can be installed wrong and run like crap without ever sending any codes to the PCM.

2. Your plug wires are the next most likely candidate. Make 110% sure they have no small singes or cracks in them anywhere. Even a small slit in one of them that at a glance may look fine, but after bending the wire a different direction may reveal that it has been damaged. This can cause the hesitation you are describing. Then make 110% sure they are properly installed entirely on the opti and to the plugs, and most importantly, in the correct order.

3. Check the coil, and the coil wire. This is a very easy fix if the coil is bad, or the wire is not properly installed as well.

4. Make sure everything you unhooked for the install has been hooked back up, such as the MAF. It's easy to forget the little things that make a huge difference.


After all of these steps have been verified, and if you still have issues, then it looks like you are in the unfortunate minority of the people like myself who installed an opti, and it still ran like crap. As far as I know your IAC doesn't need to be reset or anything. You can just replace it, and go. My particular problem was that my opti I had gotten from the factory was indeed bad. This sounds like an impossibility since it was brand new, but it was in fact a bad new part. Fortunatly, I had it replaced for free and it only cost me the pain of yanking it back out, and installing another one.

The unfortunate thing is that past the first few steps I listed above, it could be most anything, and can take forever and a half to track down. If you have the money, you might consider taking it to a dealer or shop you trust to look at it further. Whatever it is, good luck man. I have been there, and it sucks!