85 High Idle Problem

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Oct 29, 2009 | 02:22 PM

cumbercr

Thread Starter

Melting Slicks

Joined: Mar 2008

Posts: 2,141

Likes: 76

From: Santa Maria, CA

85 High Idle Problem

I've been trying to get to the bottom of a problem with idling too high. I've replaced the IAC valve and verified the throttle cable is not binding. I adjusted the TPS to .54 volts. Before I spend money on a new TPS, is there anything else I can check? By the way, I can sometimes get the idle to drop by hitting the gas pedal with the brake on and in gear.

Oct 29, 2009 | 03:50 PM

Square

Melting Slicks

Joined: Jan 2001

Posts: 2,940

Likes: 5

From: Chesapeake VA

Have you cleaned the throttle body?

Have you done a "Base Idle Reset" procedure?

What is the current idle RPM (both in gear and in neutral)?

Oct 29, 2009 | 04:05 PM

ant-knee470

Burning Brakes

Joined: Mar 2009

Posts: 944

Likes: 11

From: Davie Florida

Just a thought,

Is it possible the throttle return spring has weakened?

Ant...

Oct 29, 2009 | 04:49 PM

Sweet 90

Le Mans Master

Joined: Jan 2008

Posts: 7,030

Likes: 10

From: Edmonton, Alberta

This should be a sticky, some good info here.
Jim

http://temp.corvetteforum.net/c4/vader86/tpsiac.html

Oct 29, 2009 | 07:35 PM

fevest

Instructor

Joined: Nov 2008

Posts: 196

Likes: 3

Your throttle cable may be worn. That is what mine acted like. The cable was frayed inside and would not always return fully. Easy enough to fix, you can get cables several places.

Oct 29, 2009 | 07:41 PM

cumbercr

Thread Starter

Melting Slicks

Joined: Mar 2008

Posts: 2,141

Likes: 76

From: Santa Maria, CA

Quote:

Originally Posted by Square

Have you cleaned the throttle body?

Have you done a "Base Idle Reset" procedure?

What is the current idle RPM (both in gear and in neutral)?

I did disassemble and clean the throttle body when I replaced the IAC. I've set the idle several times per the FSM.

When it does idle properly, its around 750 rpm. The guy who burned the chip thought that would be a good idle for my combo.

Oct 29, 2009 | 07:46 PM

cumbercr

Thread Starter

Melting Slicks

Joined: Mar 2008

Posts: 2,141

Likes: 76

From: Santa Maria, CA

Quote:

Originally Posted by ant-knee470

Just a thought,

Is it possible the throttle return spring has weakened?

Ant...

Today, it was idling at 1200 rpm when I pulled into the garage. I checked all the cables while it was running. The throttle cable had play in it and the throttle was fully closed.