95 Z28 Idle problem
#17
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?
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?
#21
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
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
#23
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.
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.
#25
Re: Idle problem
#28
Re: Idle problem
@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'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.
OBD Diagnostics, Inc. - OBD2 All-In-One Scan Tool w/ USB
#29
Prominent Member
Joined: Jul 2010
Posts: 1,505
From: Born on the Florida West Coast, now where can I retire?
Re: Idle problem
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
OBD Diagnostics, Inc. - OBD2 All-In-One Scan Tool w/ USB