I've seen a faulty/erratic Opti high resolution pulse signal cause the problems you are describing. Might want to check the Opti harness connectors for corrosion and damage.

Have also seen the vacuum line to the power brake booster cause those symptoms. Check that line, including the connector on the brake booster.

For cleaning the IAC, do not use carb cleaner.... its way too harsh. Use electronics cleaner if you can. And make sure you hold the pintle facing downward, so none of the gunk/liquid gets into the tiny stepper motor that moves the pintle. Also, do not attempt to move the pintle.

 

Well the new opti has been on the car less than a week so I would hope that it's not bad. It could be faulty from the factory, but I'm optimistically ruling that one out. I know I installed it correctly because it just slid right on. No torquing the nuts to get it to seat on the dowel.

I took a good look at the opti harness and it looked great. No corrosion, no damage. I wouldn't imagine it's bad.

I'll take a look at the vacuum line to the brake booster. Maybe this afternoon, maybe the next. I cleaned the IAC yesterday but the only thing I had was brake cleaner. If I messed it up, then I'll accept that and buy a new one. I didn't try moving the pintle. I read that that was a bad idea.

 

Well since I elaborated a little too much, my original question was lost. Would a bad IAC valve cause the car to run badly in gear and at speed or would it just affect the car at idle?

 

Bump. I'd like to know whether the IAC will affect the car while I'm driving or just at idle. Thanks guys.

 

It would probably be a good idea to put a scanner on it, and watch the IAC counts when the engine is experiencing the erratic idle and "choking" feel under load/constant speed. Its hard to understand how the IAC valve would cause "choking", unless its suddenly closing off air flow completely. Even then, that should not be a significant part of the required air flow when the engine is under load and not idling. You might also want to look and see if the PCM is attempting to use the EGR system and the EVAP system at the points where you are feeling the choking. EGR isn't used at idle, but I think there are times when the EVAP opens at idle. Both are used at steady load.

 

I had similar problems.. It was my opti.. I hope the one you put in is OEM

 

i also had a loose vacuum line that popped off this week while I was trying to fix my IAC. check around your intake manifold and make sure they do not have holes in them and are connected correctly.

 

I'll have to see if I can find a place to do it. The guy I know is only available on weekends and I don't want to bother him on Christmas weekend. But I'll keep this in mind for when I am able to get it checked out. Also, my AIR and EGR systems are both deleted and tuned out. Would this negate what you said about the EGR system being used?

I bought it from "thepartsladi" on eBay. As I understand, it is.

Actually I do have some bad vacuum lines. One is going into the passenger side of the TB. I forget which one the other one is. I'd have to go check.

 

yeah the one that popped off was connected to the purge solenoid and went to the TB, so that could make things get silly. keep on trucking buddy, you will figure it out!

 

A vacuum leak in the line from the EVAP solenoid to the throttle body would certainly cause idle quality problems.

If your EGR was tuned out correctly, it should have no affect on how the engine runs. AIR is not an issue either way. I didn't mention AIR.

 

Would it also cause problems while running?

 

oh yeah, a loss in power and backfiring when getting off the gas

 

Sounds like what my car's doing. I'll check it out as soon as I get time.

 

Ok, I got around to taking care of my dry-rotted hoses today. I had two of them. In this diagram (from shoebox's website, thanks!) they are number 5 and number 14. I didn't have time to get replacements today so I heat-shrank them with 1/4" heat shrink tubing. Temporary fix FTW! (I'll get real replacements later) Anyway, the problem with it stumbling and surging under throttle seems to be taken care of. It's still choking down and surging at idle though. Any ideas?

 

is your rubber intake elbow on the hole way or does it have any tears in it? I had that problem awhile back and had to buy a new elbow. is your MAF connected on there properly?

definitley buy some new vacuum lines if you can, I know its not cheap, but the smallest hole caused a huge problem with my car.