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Throttle body adjustment / IAC Count on 88 V6 by Cplensdorf
Started on: 02-20-2004 10:13 PM
Replies: 14
Last post by: Cplensdorf on 02-25-2004 07:29 PM
Cplensdorf
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Report this Post02-20-2004 10:13 PM Click Here to See the Profile for CplensdorfClick Here to visit Cplensdorf's HomePageSend a Private Message to CplensdorfDirect Link to This Post
Ok, I went ahead and messed with the adjustment screw on the throttle body fully aware of how many turns each way I adjusted...and as I went back and forth just looking at what the effect was, I kinda lost count...very stupid, yes!

So when resetting this, I understand that it can be reset by looking at the ECM counts for the IAC. Is this the correct method, or is there another way?

If so, what step count should it be at?

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Cplensdorf
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Report this Post02-21-2004 10:21 AM Click Here to See the Profile for CplensdorfClick Here to visit Cplensdorf's HomePageSend a Private Message to CplensdorfDirect Link to This Post
Anyone?
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FrugalFiero
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Report this Post02-21-2004 11:05 AM Click Here to See the Profile for FrugalFieroDirect Link to This Post
Question? Why were you messing with the screw on the throttle body? If your idle was too high before you turned the screw, there is a good chance you have a vacuum leak. Too low / stalling the likely cause is IAC motor / port gummed / clogged. Idle is controlled by the ECM and associated sensors / IAC motor. Try adjusting the throttle plate screw till the plate is just barely cracked open. Remember almost all idle air flows thru the IAC port, not the throttle plate. If anyone has anything to add, or correct, please do!

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Tim
Red 88 Formula Auto 2.8 100K+ Miles - Hypertech - No Cat - No EGR

Murphys Law - "Nothing is as easy as it looks, Everything takes longer than you expect, And if anything can go wrong - it will, At the worst possible moment!"

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ryan.hess
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Report this Post02-21-2004 01:11 PM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
I'm not positive on IAC counts, but for my grand prix, (and most likely your fiero as well), you have to ground the ALDL port (as if you're checking the codes), wait 45 sec, unplug the IAC, start the engine, and adjust the idle using the screw to 500-600rpm. This is on a warm car btw. Then shut down, plug in the IAC and reset the computer.
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Chicken McNizzle
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Report this Post02-21-2004 03:25 PM Click Here to See the Profile for Chicken McNizzleClick Here to visit Chicken McNizzle's HomePageClick Here to Email Chicken McNizzleSend a Private Message to Chicken McNizzleDirect Link to This Post

Here, I wrote this tech article years ago to help people like yourself in need of info......Idle Mystery


....And by the way, NEVER adjust the throttle blade by removing the plug adjusting the set screw and turning the screw, you may cause the butterfly to be open to far thereby allowing air past it and not past the IAC valve which in turn makes the IAC valve nonoperational - the result from this will be the IAC valve constantly fighting to set the idle and the idle will be erratic.

The article answers just about everything you need to know

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Cplensdorf
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Report this Post02-21-2004 04:18 PM Click Here to See the Profile for CplensdorfClick Here to visit Cplensdorf's HomePageSend a Private Message to CplensdorfDirect Link to This Post
OK, OK!!!!! I know I should not have done this...I was not attempting to set the idle this way...I was messing around with winaldl and had a little extra time on my hands....I have been searching to no avail for months on why my fiero is detonating....I read the article posted above and wanted to verify the throttle blade was in the proper place, as my IAC did not appear to be working properly....well, I messed with it and I lost count of the turns....

BTW - I found info on a Buick GN site (guys that were reprogramming the ECM) that seriously questions the "unplug ALDL, adjust to 500rpm" method (i already did this) and says the proper way is to set theirs to 10-30 steps when viewed by a scanner...

Thanks for the info guys

Anyone else?

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FrugalFiero
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Report this Post02-21-2004 04:36 PM Click Here to See the Profile for FrugalFieroDirect Link to This Post
 
quote
Originally posted by Cplensdorf:
I have been searching to no avail for months on why my fiero is detonating....I read the article posted above and wanted to verify the throttle blade was in the proper place, as my IAC did not appear to be working properly.

Anyone else?

Detonation...Idle problems...could it be...the dreaded vacuum leak?

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Tim
Red 88 Formula Auto 2.8 100K+ Miles - Hypertech - No Cat - No EGR

Murphys Law - "Nothing is as easy as it looks, Everything takes longer than you expect, And if anything can go wrong - it will, At the worst possible moment!"

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TK
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Report this Post02-21-2004 04:40 PM Click Here to See the Profile for TKSend a Private Message to TKDirect Link to This Post
I would shoot for 30-50 with 60 being max. 80 will set a code.

I know some of the Regal guys like the low numbers but I like to have a bit more range down there. It also helps cut down on the start up flair. I have a Turbo Regal and I go a bit higher than some.

There is nothing wrong with using the minimum idle method or IAC counts directly. I usually go for the counts but that assumes everything is working correctly and the IAC and TB are clean.

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Cplensdorf
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Report this Post02-21-2004 05:00 PM Click Here to See the Profile for CplensdorfClick Here to visit Cplensdorf's HomePageSend a Private Message to CplensdorfDirect Link to This Post
Frugal, I wish it were that easy! I challenge anyone to find a vaccum leak on my engine. In fact, I would pay someone $100 if they could find a vacuum leak...I have torn the top end down twice and been over it numerous times over several months, tested every hose individually with a gauge, EGR, new solenoid, new egr tube, new throttle body, new IAC, new TPS, new intakes, etc...I have had the car diagnosed professionally (?) and by every person I know....no one has ever seen this problem I am having.....thats another story though...

TK, thanks for the info. Any reason for the numbers other than to allow motion each side of the base setting? My TB and IAC are both brand new with less than 1 hr on them (no its not in a boat, I just have not been able to get the thing on the road the way it is)....When setting the counts do I do so with everything plugged in or in diag mode with the ALDL grounded?

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Chicken McNizzle
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Report this Post02-21-2004 05:32 PM Click Here to See the Profile for Chicken McNizzleClick Here to visit Chicken McNizzle's HomePageClick Here to Email Chicken McNizzleSend a Private Message to Chicken McNizzleDirect Link to This Post

Also, the quick way to reset the IAC is to run the car in diagnostic mode ( grounding pins A and B in the ALDL ). With the ignition on and engine not running, you will hear the stepper motor forcing the IAC plunger into the bore and bottoming out, this will sound like a vibration or clicking coming from the TB. When the engine is run this way the SES light will flash lean or rich.

I would root out the possibility of a dirty IAC plunger or TB as both units are new, however vacum leaks do happen - one quick way to check is to run the car and plug the IAC port ( inside of TB bore - must remove rubber intake elbow for access ) and simply plug the hole with your finger - if the car continues to run, at any RPM, there is a leak.

One often overlooked vacum route is the steel line to the brake powerbooster, this can be confirmed by simply plugging the vacum port that supplies this near the MAP sensor

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FrugalFiero
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Report this Post02-21-2004 08:24 PM Click Here to See the Profile for FrugalFieroDirect Link to This Post
 
quote
Originally posted by Chicken McNizzle:



One often overlooked vacum route is the steel line to the brake powerbooster, this can be confirmed by simply plugging the vacum port that supplies this near the MAP sensor

Also the power brake booster itself can leak, and still seem to work fine.

Edit for: Also has your fiero done the detonating since day one? Since you've done alot of work already could it possibly be the wrong prom or ECM?..Just a thought.
-----------------
Tim
Red 88 Formula Auto 2.8 100K+ Miles - Hypertech - No Cat - No EGR

Murphys Law - "Nothing is as easy as it looks, Everything takes longer than you expect, And if anything can go wrong - it will, At the worst possible moment!"

[This message has been edited by FrugalFiero (edited 02-21-2004).]

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Cplensdorf
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Report this Post02-22-2004 09:58 AM Click Here to See the Profile for CplensdorfClick Here to visit Cplensdorf's HomePageSend a Private Message to CplensdorfDirect Link to This Post
Frug,

Yes, the engine has done this since its startup. It is a rebuilt bottom end (to 3.1) and everything else to the air cleaner is BRAND new from a crate motor. PROM/ECM from the same car 88 GT that worked fine prior to removing engine...

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NotAFieroAnyLonger
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Report this Post02-22-2004 10:50 AM Click Here to See the Profile for NotAFieroAnyLongerClick Here to Email NotAFieroAnyLongerSend a Private Message to NotAFieroAnyLongerDirect Link to This Post
 
quote
Originally posted by Cplensdorf:

Frug,

Yes, the engine has done this since its startup. It is a rebuilt bottom end (to 3.1) and everything else to the air cleaner is BRAND new from a crate motor. PROM/ECM from the same car 88 GT that worked fine prior to removing engine...

I have an 87GT Auto ECM if you need just pay for shipping...

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FrugalFiero
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Report this Post02-22-2004 11:28 AM Click Here to See the Profile for FrugalFieroDirect Link to This Post
Is the top end (heads in particular) stock? There has been some info on this forum about getting the right pistons if you go to aluminum heads...have you taken any compression readings? Sure you got the right pistons in it? Maybe a 3.1 member can chime in here...

------------------
Tim
Red 88 Formula Auto 2.8 100K+ Miles - Hypertech - No Cat - No EGR

Murphys Law - "Nothing is as easy as it looks, Everything takes longer than you expect, And if anything can go wrong - it will, At the worst possible moment!"

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Cplensdorf
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Report this Post02-25-2004 07:29 PM Click Here to See the Profile for CplensdorfClick Here to visit Cplensdorf's HomePageSend a Private Message to CplensdorfDirect Link to This Post
Pistons are the correct ones...I have gone that route already...Compression was as roughly 154-159 on each cylinder.....any other ideas would be helpful.
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