LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

95 Z28 Idle problem

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Old 11-15-2023 | 09:16 AM
  #16  
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Re: 1995 z28 idle issue

Yeah resetting isn’t doing anything so I’ll have to repull it
Old 11-15-2023 | 12:24 PM
  #17  
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Re: Idle problem

You need to reference the 1995 factory service manual. The IAC removal and adjustment procedure is shown on page 6E3-C2-16. Read "Measure (if Installing a New IAC Valve)". The distance between the tip of the IAC valve pintle and the mounting surface must be 28mm or less. See the next page for a diagram (Figure C2-18) showing where to measure "distance of pintle extension". Note that you do not rotate the pintle. You just apply gentle pressure if it's too long. That only works with a new valve. It can damage a used valve.

The PCM has no way of knowing how long the pintle is. It moves the pintle in "steps" (counts) inward and outward, but you have to set the starting position.

Are you sure the throttle blades are closing against the throttle stop screw, and not hanging up due to a weak spring?
Old 11-15-2023 | 01:36 PM
  #18  
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Re: Idle problem

Yes but After cleaning the buildup on both sides of throttle plates I can see gaps between the throttle plate and throttle body. Should there be no gap?
Old 11-15-2023 | 01:46 PM
  #19  
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Re: Idle problem

Also I’ve noticed it doesn’t go down when in gear anymore it stays at 1000ish rpm’s in and out of gear what does this mean?
Old 11-15-2023 | 01:53 PM
  #20  
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Re: Idle problem

Also do you have a Aldl cable that you back and recommend? I have the obd2 socket but obd1 pcm
Old 11-15-2023 | 01:59 PM
  #21  
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Re: Idle problem

Stock or aftermarket throttle body?

Throttle body that was on my Formula when purchased new:

EDIT - problem with links. Photos in post #23, below

Last edited by Injuneer; 11-16-2023 at 08:57 AM. Reason: Bad links - pictures posted below
Old 11-15-2023 | 02:07 PM
  #22  
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Re: Idle problem

Neither of those link work for me “404 not found”
and it’s stock which I believe is 48mm
Old 11-15-2023 | 02:40 PM
  #23  
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Re: Idle problem

Don't know what to tell you about the links. They are for photos in my profile album on this site.

Yes, stock is 48mm

Front of stock:


Back of stock:


Aftermarket Holley 58mm:


The Holley actually had a space around each blade when I bought it. The shop that built the engine noticed it too. But we weren't running the engine on the stock PCM at that point. A while later doing a burnout at the track, I had a nitrous backfire in the intake manifold (one of the solenoids was leaking) and the bottom of each blade was bent outwards at 90-degrees. I gently hammered the blade back to flat. Then I though about it a bit more, and since the blades were off the throttle body, I gently tapped the outer edge of the aluminum blade, and expanded it enough to eliminate the big gap, rounded the blade with a file to eliminate the gap.
Old 11-16-2023 | 08:50 AM
  #24  
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Re: Idle problem

The links don't work for me, either, Fred. 404
Old 11-16-2023 | 09:23 PM
  #25  
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Re: Idle problem

Originally Posted by Ayjomi
Also do you have a Aldl cable that you back and recommend? I have the obd2 socket but obd1 pcm
Try this link to make your own

https://www.camaroz28.com/forums/com...7/#post7016688
Old 11-16-2023 | 10:33 PM
  #26  
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Re: Idle problem

Originally Posted by Ayjomi
Also do you have a Aldl cable that you back and recommend? I have the obd2 socket but obd1 pcm
@GaryDoug

I'll ask the author of Scan9495 to recommend a ready made cable. His experience with cheap Chinese D-I-Y parts indicates there are major QC problems.
Old 11-16-2023 | 10:51 PM
  #27  
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Re: Idle problem

Originally Posted by Injuneer
@GaryDoug

I'll ask the author of Scan9495 to recommend a ready made cable. His experience with cheap Chinese D-I-Y parts indicates there are major QC problems.
If you checked my post (Injuneer) you will see they are GENUINE PARTS!
Old 11-17-2023 | 07:48 AM
  #28  
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Re: Idle problem

Originally Posted by Injuneer
@GaryDoug

I'll ask the author of Scan9495 to recommend a ready made cable. His experience with cheap Chinese D-I-Y parts indicates there are major QC problems.
I purchased this cable a while ago. Works like a champ, and it's not Chinese as far as I can tell.

OBD Diagnostics, Inc. - OBD2 All-In-One Scan Tool w/ USB
Old 11-17-2023 | 10:34 PM
  #29  
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Re: Idle problem

Originally Posted by Hamip
I purchased this cable a while ago. Works like a champ, and it's not Chinese as far as I can tell.

OBD Diagnostics, Inc. - OBD2 All-In-One Scan Tool w/ USB
That will work. however do not be fooled. Some parts of that cable are made in China.
Old 11-18-2023 | 06:05 AM
  #30  
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Re: Idle problem

Originally Posted by GaryDoug
That will work. however do not be fooled. Some parts of that cable are made in China.
Good to know. Thanks.


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