Deenasty

I was having a low idle at stops, and occasional shut offs. I scanned the car, turns out that the IAC was at 160!! I got it down to 27, with the idle turn screw, but now experience a bit of a high idle. What should I set the IAC at? Thanks!

shoebox

You can't really "set" the IAC. It is set by the PCM in response to other inputs. It was apparently trying to let more air in and you were able to compensate by opening the throttle blades. Typical idle IAC counts are in the 20-40 range for stock or near stock. You may have an overly rich condition that is trying to be compensated for.

Deenasty

Yes the car is not fully tuned yet, and I can smell the richness. So is there anything I can do, to get the idle down a bit? Should I just close the blades down a bit?

HBHRacing

compinsating for IAC counts with changeing the idle screw is not a real good idea. do you have a stock throttle body? you need to find out what is causing the IAC to want to be open almost all the way. what ever the prblem is the computer is seeing it and trying to keep idle up.

Deenasty

its a 52mm bbk, It is my cam 240/240 595/595 112....

Injuneer

I looked at the scan you sent me a while back.... your "target" idle speed is 937rpm. You are going to see more than 20-40 IAC counts to achieve that level. Your previous log showed 77-90 counts. When did it decide to go to 160?

Check the idle air passages in the BBK, starting with the opening between the bores.... they typically leave "flash" in that hole, or don't bore it out all the way. Then check the passages all the way down to the bottom cover plate, to make sure you don't have anything in there blocking flow.

With a 240deg 112LSA cam you aren't going to have a smooth, low speed idle. Someone has bumped the target idle up to compensate, but its going to take some talented tuning to get it smoothed out and manageable. How big are your injectors?

HBHRacing

your going to have to set the idle on the TB due to the aftermarket TB. your on the right track. you just have to make sure that your idle is set to 800rpm for M6, 550rpm for A4 in neutral and the IAC counts are between 20-40. i'm not sure exactly how your cam is gong to effect the set idle but i would assume it will be a little higher then stock settings

once you are in range you need to look at teh TPS voltage
you want it at aprox 0.75V. If you are not near this range you will have to remove the TPS and take a dremal or similar and slot the bolt holes so that you can rotate the sensor. Once you are in spec you are good to go

Deenasty

my injectors are SVO 30lbs... So what should I start off by doing first? First check passages, then set IAC which im thinking it is going to be around 70-90? Then check the voltage on the TPS? Thanks a lot for helping me guys...And for your patience dealing with a beginner

Injuneer

Your previous scan showed closed TPS voltage at 0.69 V. There is nothing wrong with that.

My concern would be why something "changed"? It was idling about right before..... moving moderately between 925rpm to 950rpm, against a target of 937rpm. That means the idle was "in control".... IAC was 77-90, TPS was 0.69V, RPM was 925-950.

Now you apparently have a situation where IAC has jumped to 160, and your idle is out of control. What, if anything did you change during this period?

Have you checked the IAC valve per the instructions on Shoebox's website?

Do not evaluate this cars performance against a "stock" LT1.... you can't simply assume that a fairly healthy 383 with a big cam is going to act just like a stock 350.

Deenasty

I started getting a low idle. So low that the car would shut off when I came to a stop. Even if i was crusing at say 40mph, and stuck the clutch in, the car would Idle lower, than what my rolling speed was. I began to look for possible vacuum leaks, iac, things like that. I was getting codes for MAP too high, and one code for EGR fault. I changed the MAP, and the EGR solenoid. Still idled low here and there at stops. I went ahead and scanned the car, and the IAC was at 160! I went ahead and opened the blades until the IAC dropped down. Now idles fine, except at stops it idles high, then takes a while to drop down. The IAC is brand new, less than 2k miles on it. I even took it out and cleaned it. Now I need the idle to drop down a bit, so i was assuming that I had to close the blades just a tad, but I was assuming that there would be a good point to set the IAC counts in order to make my idle just fine. I guessed wrong That was the only thing I changed. Oh and new o2's, and replaced a burnt wire.

HBHRacing

have you taken a vacuum reading? the MAP voltage high code could be from the cam causeing low vacuum. really the EGR fault could ahve been the same reason since the MAP is not reliable when it;s needed for the EGR test. I would be cuorius to see just how much vacuum your pushing

Injuneer

The fact that it was working, then stopped working, even though the PCM told the IAC to open to 160 steps would indicate that the IAC motor didn't move in response to the PCM command. By forcing the throttle blades open, there's a good chance you have thrown the TPS sensor out of whack.

Deenasty

I have not taken a vaccum reading, I will today. What do you mean out of wack, how can I get it back in wack? hahah DO you mean the sensor is no good? or should I just check its voltage when I scan it today? Should it be at around .54 or.55 ?

HBHRacing

the sensor sends resisted voltage signal to teh PCM based on the amount the arm is truned. when you adjust the throttle blade it also turn the arm on the TPS slightly and will change the voltage reading to the point were it could cause an issue. most people like to se right about 0.75 volts at closed throttle. since you said that you tried to compinsate by adjusting the throttle screw thats why I posted about trying to get idle, IAC and TPS volatge back to where it needed to be. as stated by looking at a log your desired idle has been changed for the cam so you need to use that reading to baseline the idle and then look at the IAC counts. due to the cam you will have a hard time getting things where they need to be but 160 was just way way too far out. The last step after idle and IAC counts is TPS voltage like said above.

I can not honestly say how the cam will effect the IAC counts. but if it works like low vacuum it would actualy lower the counts cause it would try and compinsate for higher idle but again. I cna;t honestly say.

smoknta

I have been told by a very well known Tuner, that when checking the IAC counts you need to check them. Make an adjustment. Shut the car off and check them again. And repeat this process until the desired results are reached. I had a lot of problems with my BBK throttle body until i made a few modifications.
Here is somthing similiar:
http://jrevans.fbody.com/car/TB_mod/
I've also got a 383, a BBK 58mm throttle body, 30# svo's.