TTA IAC adjust different than TR?

[tminer]

I noticed a difference in the IAC adjustment procedures for the TTA (c/o 89tta.com) and TR (c/o gnttype.org). Most noticable was setting the base idle in Park (TR) or Drive (TTA).

Is this just different strokes for different folks or is there a difference in the stock eproms that comes into play?

TIA,
Tom

 

[2QUIK6]

I don't know of any differences,my preference is to set it in Drive under load, thats where it matters in order to correct off idle stumble.

 

[mark b]

Are you setting using a scanmaster or the like? If so, I agree... in "Drive" seems to yield the better results.

Did you remove it and clean it? They get dirty easy and can clog that pintle thing in there.

 

[3.8TransAM]

I agree with 2Quik6.

Set it under load to minimize the actual IAC at idle. (my TPI stuff I tune I might see 1-5 at idle maybe once or twice for 2hr datalog)

The turbo cars and my TTA I have done seem to like it roughly 1-10 steps at idle in gear for best results.

It takes a few times to get it right lol So dont get frustrated if your fisrt attempt fails.

Also find out at what idle your chip maker has the chip set for also, so u dont chase yourself in circles.

Dont foget to keep track of your TPS to make sure tis setting stays correct also and adjust as necessary.

later
Jeremy

 

[src76ta]

2QUICK6, my car some times bucks getting back onto the fuel from a coast and off the fuel from a steady peddle. Is this what you mean by off idle stumble?

 

[tminer]

I am not having a problem per se, just curious as to why different techniques.

3.8TransAM has it right, the idle is controlled by the eprom. The adjustment is just to get the mechanical system (the throttle blade and TPS sensor positions) calibrated to a specified state so that the computer can control the engine properly.

Thanks,
Tom

 

[2QUIK6]

Originally posted by src76ta
2QUICK6, my car some times bucks getting back onto the fuel from a coast and off the fuel from a steady peddle. Is this what you mean by off idle stumble?

Off idle stumble is characteristic of the hesitation when taking off from a dead stop, ...removing foot off brake and stepping on the gas pedal...if there is a slight hesitation, thats the "stumble". Usually is related to the IAC being too far open when stopped and then hitting the throttle is allowing too much air to get in the plenun too fast for the amount of fuel being injected.....could be a few other problems, but IAC adjustment is usually the cause.

Your problem sounds like something wrong with AE fueling and DE fueling on decelleration...maybe a leaky injector or stuck injector....may do a injector leak test by seeing if the rail holds pressure for 10-15 minutes minimum with key off....if not, then pinch off the rubber fuel lines above the rear axle after energizing the pump to get pressure and once pinched off does pressure continue to drop....if so, leaky injector.
Pinch them off with a pair of vice-grips...both lines at same time.

 

[Razor]

I dunno, i've always set IAC in Park engine idling. See the way I look at it is that the lowest possible number your to see can only happen when the vehicle is in park without any loads. Any condition that creates load will obviously increase IAC. Lights, AC, power steering, etc..

So if the ol saying is.. any number above zero.. I typically have setup my IAC for 10-20 at Idle in Park. And never have had any issues whatsoever with tip'in/stalling/etc...

If setting in drive works for ya'll.. what can I say

 

[83ttypecooled]

Hi,
Every vehicle I have seen always was close to IAC 10-20 hot at idle in neutral/park, when it was idling correctly. Just a thought.

 

[tminer]

I checked mine last night and it was 40. That seems perfect to me if 80 is the max. Helms shows 80 or less and greater than 0.

Low numbers can effect wear as they might cause the pintle to bottom out if the ecm trys to correct to or below 0.

Helms also doesn't recommend adjustment unless the TB is being replaced. That is why the cap is on the adjuster, to seal the factory setting. But if it does need set then it's 500 +/- 50 rpm in Park.

Personally, I think that as long as the chip idle speed can be maintained in Park or in gear, then the IAC is doing it's job. Tip in stumble or other issues would be caused by something else and fudging the IAC to correct them is a bandaid.

Tom

 

[Razor]

Originally posted by tminer
Low numbers can effect wear as they might cause the pintle to bottom out if the ecm trys to correct to or below 0.

Tom

Tom, if the number for any reason goes to zero.. there are some other issues. Personally 40 is too high at idle no loads on engine. High IAC numbers means it has to really pull the plunger in, and this pulling the plunger in may limit its effective range.

Again, this is a personal thing of what works best. 10-20 at idle in park is plenty. And trying to adjust with the RPM 500 +- 50 rpm.. forget it. You'll do the procedure 10 times and never get it rite.

Use the scanmaster.. open the blade a little it drops IAC. Close blade.. it increases them. Setting TPS after its been calibrated.

Yes it never has to be done, unless there has been a change to the engine.