IAC reading ?

[dentmasters01]

car idles fine, but scanmaster reads 0 on the iac at idle. I've screwed the throttle up and down. The reading gets higher as the butterfly is opened but settles back at 0 when the screw is turned back down.... any ideas ?

 

[FreeBoost]

Adjust so the IAC reads 10-30

 

[BRAD_PADGETT]

I would take the IAC valve out and clean it and clean electric connectors on the IAC. Retest. If the car idles fine and you still get the same reading forget about chasing it down. It will drive you nuts chasing the issue and this setting only affects idle. My car idle hunts due to the wideband o2 sensor and powerlogger. Good luck- Brad

 

[dentmasters01]

Adjust so the IAC reads 10-30

thats what I'm trying to do. If I get it to 10 the car is idleing at like 2k.

Brad, I've tried taking it apart and cleaning it and now i'm leaning towards the idea of just ignoring it as the car does perform ok.
thanks

 

[Smokin-6]

thats what I'm trying to do. If I get it to 10 the car is idleing at like 2k.

Brad, I've tried taking it apart and cleaning it and now i'm leaning towards the idea of just ignoring it as the car does perform ok.
thanks

Make sure your TPS is set at .42-.44 when warm and idling. If your changing your IAC the TPS will change.

 

[Chuck Leeper]

"The reading gets higher as the butterfly is opened but settles back at 0 when the screw is turned back down.... any ideas ?"
Should get lower as you bleed in air w/ the throttle blade.

 

[dentmasters01]

Make sure your TPS is set at .42-.44 when warm and idling. If your changing your IAC the TPS will change.

Its at .42 at idle. The instructions say to set the iac then set the tps so that's what we tried. when we could never get the iac set we just skipped it and set the tps.

 

[dentmasters01]

"The reading gets higher as the butterfly is opened but settles back at 0 when the screw is turned back down.... any ideas ?"
Should get lower as you bleed in air w/ the throttle blade.

......now you see what i'm dealing with......

could this be a bad iac valve that just happens to not affect the way the car idles ??

 

[TurboDave]

Time to start all over. Try this:

The little set screw that controls IAC readings, turn it so that you can only see 1/2 to 1 thread coming out of the FRONT side of that block that it's screwed into on the throttle body. At this point it will just be touching the tang on the throttle.
Now, reset the TPS to read .42 (key on engine off).

Start it up and let the engine get warmed up, preferably with a little drive around your sub. Never rely on taking readings just letting the car sit and warm up (unless it's un-driveable).

What's it read now?

Remember: Turning the air bleed screw (what most people mistake for idle speed screw) CW (clockwise) will result in a momentary increase in rpm, but (if the IAC is not reading 0) the IAC value should decrease to maintain idle speed.
Turning the air bleed screw CCW (counter clockwise) will result in a momentary decrease in rpm, but it will come back because you will see the IAC value increase to maintain idle speed.

CW=decrease IAC value
CCW=increase IAC value

All the time, remembering to reset the TPS to maintain .42-.44 (you don't have to do this with every turn of the screw, but if you have to make a couple turns, stop and adjust TPS) When your IAC number is close, double check proper setting of TPS.

 

[dentmasters01]

I understand what the functions of each part are, but they are not operating that way. I don't have a problem with the tps setting, only the iac. I think its a bad valve, although i spoke with richard clark and he suggested unplugging the iac, get the car to idle at about 500 rpm then plug it back in and see if it functions properly and brings the car back up to idling correctly.

 

[turbojd]

First I would take out the IAC and clean it real good with some carb cleaner or brake cleaner, also clean the throttle body and plate area. Next re-adjust your IAC and TPS. IAC Reset Procedure

 

[TurboDave]

I understand what the functions of each part are, but they are not operating that way. I don't have a problem with the tps setting, only the iac. I think its a bad valve, although i spoke with richard clark and he suggested unplugging the iac, get the car to idle at about 500 rpm then plug it back in and see if it functions properly and brings the car back up to idling correctly.

OK, but understand, if it's WAY out of adjustment, it will not behave as expected.
Might want to pull it out and clean it up some, and inspect the gasket.

 

[turbojd]

And do not over tighten the IAC when reinstalling it!

 

[Razor]

If your IAC reads zero.. your blade is way too open or you have a serious vacuum leak.

So if you close the blade(like trying to bring down the rpm's) the IAC will increase from zero IF the TPS is between the .38 and .46 and the "chip" allows it.

What I do, is if its at zero, close the blade... set tps to like .42.. now go and drive the car around the block.. when you get back home.. look at the IAC number. With a closed blade it should read pretty high. From there make small adjustments.

Adjusting the IAC with a scanmaster is simple IF the chip lets you .. so to go around it.. the car must be driven.

Understand any time any accessories are turned ON.. like AC, Fan, lights, etc.. the IAC will increase. So your 10-20 IAC is idling in park no accessories working.

HTH

 

[Real-T]

Just out of curiousity what are your O2's doing at idle?

What chip and/or fuel control system are you using?

I would agree with Brad_Padgett and say that if it is working fine you can "choose to ignore it" for now as it will drive you nuts hunting it down.

I was working on a car previously that had the same thing where despite all the proper adjustment procedures the IAC number still would not agree but the car seemed to idle fine.

One thing that I found was that the O2's would read low but still not affect the idle quality, however after a long time at idle (3-5mins) the SES light would come on as the O2 would not crosscount.

Just for fun I decided to see what would happen if the O2's were brought in line. This car had a MAFT Pro on it, so I added fuel until the O2's came in line and started crosscounting at a good rate (and the WBO2 also hovered around 14.7) at idle.

With that settled the car idled better so I did the normal IAC reset procedure and that seem to cure it in that the IAC numbers were now hovering on or around 25-30, the O2 numbers were in line and the car actually idled smoother.

I am not saying it will be your issue but just as an experiment maybe you can try something like that?