hello,

after my new engine set up done. I never succed getting correct numbers from my IAC.

I end up my buying a new IAC and tried again to have correct values :
What i get is :

* IAC stay at 75 and never move below. it can move upper,
* i dont succeed having the correct IAC counts with any idle
* if i engage gear, IAC move up to 160

i've checked for vaccum leaks a very lot of time but haven't found any.
I don't know where the pb can be.

Before having the problem, i changed : LE2 heads, LE1.5 cam, 30 ford racing injectors, 52 mm Holley TB, Ion tune.

Any idea on what to check ?

Pierre

 

With the new throttle body and new cam it looks like you need a little more air at idle. Try cracking the TB blades open just a little more with the throttle stop screw (Make sure you check your TPS reading with a meter or scanner to keep it in the right range. Slot the TPS mounting holes if you need to adjust it). That should lower your IAC counts.

A vacuum leak would make your IAC counts lower, not higher.

 

The IAC staying open wouldn't be the sign of a vacuum leak. As Shoebox pointed out, the engine needs more air to idle than its getting through the clearance in the TB blades and the idle air passage.

 

ok, not to steal his answers, but.... i'm having similar issues with a 52mm bbk/edelbrock unit. that same setup ran and idled fine, but i put in a custom cam and now i can't get the idle down. it will start and idle fine, but then once you drive it, it idles high at every stop sign....maybe 1500 rpm. sometimes if you drive it hard enough, it will idle at 3000 rpm. if you shut it off and restart it, it still idles at that same rpm. i've tried opening and closing the tb blades and nothing seems to help. what can be my issue there?

 

Blackztpi what do the timing and the iac counts look like during these events? What does the tps read?

To the op, like everyone has said before open the tb blades up a little.

Also just in general i like for my iac numbers to be somewhat higher than normal with larger cams it helps to balance out the blm's at idle. That along with a little selective individual cylinder fuel trims at idle will get you in good shape.

 

Really not a good idea to highjack someone's thread, particularly when your problem (idle too high = too much air) is not the same as his (IAC open to far to maintain idle = too little air).

 

fred what should his iac numbers look like, or what do you like to see

 

i tried to opened the blades more but the only thing i can see is my idle going over the target idle ( (and IAC stays at 75)


also i have a DTC code 33 occuring sometimes (not always) at idle. maybe the problem can come from somewhere else ? misfires ?

 

We would hope if it is misfires, you would be able to feel that. You could check primary temps immediately after start up for dead cylinders. If your idle is too low, a 33 could result.

You should check the MAP for signs of the source of the 33 code. With KOEO check the grey to black wire for 5 volts. Then scan it to see if manifold pressure equals atmospheric, again with KOEO.

 

You should definitely see a change in IAC readings and idle should settle down to target. Did you do an IAC reset when you installed the new IAC? While you might be able to override the target RPM with too much TB blade adjustment, the computer is what controls the idle and should handle it in most cases.

Your code 33 could be from your cam or erratically low idle.

 

Obviously, a modified engine with a cam isn't likely to run 20-40 at idle, like a stock engine. So running a bit higher isn't really a concern. Problem is, with it idling at 75 in neutral, and then maxing out with the tranny in drive, it would seem to indicate the engine is not getting enough air. Possibly the idle air passages are plugged up, the IAC motor isn't actually moving, or something similar. Also odd that opening up the blades increases the idle speed, and does not produce any reaction from the PCM with regard to IAC counts.

When you installed the 52mm TB, did you check to make sure there was no casting flash in the IAC passage? Are you sure you have the gasket for the bottom plate that holds the IAC motor aligned correctly?

What did the tuner set the idle speed at in neutral? ... in gear? What idle speeds are you seeing?

 

sorry bout the hijacking...i just thought it would be better to throw out a quick one rather than to repost another thread.

 

I looked in the IAC passage and didn't mention anything bad.

About IAC motor alignment , i will check again on the week end.

Tuner set idle at 875 for both neutral and gear.

I will look again for everything during the week end and report you what i found.

Thanks for your help

 

DId you pull the ecm fuse to clear the ecm?

Seemed to help mine, Mine stays around 75 ish in gear. What does your MAP, MAT(IAT) read?

David

 

You may need to drill a hole in your throttle body, the stock throttle body has a hole that diverts air to an alternate passage into the intake manifold (between the throttle body blades). Many aftermarket throttle bodies dont have that hole, so they end up blocking the alternate passage in the throttle body

The IAC tries to compensate by opening at a faster rate to maintain the airflow at idle.