"Factory" Idle Speed

Reply Subscribe

Thread Tools

Search this Thread

Aug 18, 2016 | 08:20 PM

MitchV

Thread Starter

Advanced

Joined: Nov 2015

Posts: 50

Likes: 8

From: Chicagoland IL

"Factory" Idle Speed

I'm unable to find a rpm idle speed number in the FSM. My '93 LT1 runs great, idles smooth, but idles just under 500 rpm's in drive. Seems a bit low. Is this typical?

Aug 18, 2016 | 08:24 PM

Tom400CFI

Team Owner

Joined: Aug 2004

Posts: 21,543

Likes: 3,216

From: Park City Utah

That seems low to me too. I'd bet that your IAC valve is 10-7. Does it idle significantly higher when cold?

Aug 18, 2016 | 08:37 PM

MitchV

Thread Starter

Advanced

Joined: Nov 2015

Posts: 50

Likes: 8

From: Chicagoland IL

It does idle higher when cold, but just about 500 rpm's. The idle also goes up a small amount when the a/c is on. Still under 500 rpm's.

Aug 18, 2016 | 08:45 PM

Tom400CFI

Team Owner

Joined: Aug 2004

Posts: 21,543

Likes: 3,216

From: Park City Utah

Can you get it on a scan tool and see what your IAC counts are? Maybe that idle isn't too low, but my '92 (6 speed) idles at ~750 or so.

Aug 18, 2016 | 09:02 PM

MitchV

Thread Starter

Advanced

Joined: Nov 2015

Posts: 50

Likes: 8

From: Chicagoland IL

Thats a negative on the scan tool. I may just leave well enough alone, unless it gives me drivability issues.

Aug 19, 2016 | 05:09 AM

STL94LT1

Race Director

Joined: Jan 2002

Posts: 12,261

Likes: 85

From: O'Fallon Missouri

A4 in gear, 550 rpms at idle.

Oct 2, 2016 | 03:01 AM

larry_c4

Intermediate

Joined: May 2015

Posts: 45

Likes: 1

From: Philadelphia PA

I have been having this issue with my '92 Auto as well. I have tried everything. Mine idles smooth at 500 RPM steady(in drive). Seems low to me and everyone who rides in it. Feels low like it is about to stall at red lights/ stops,but it never does. Runs great otherwise. I have Cleaned the TB/IAC, new injectors, Rebuilt ECM, New Delco Opti, plugs/wires, air filter. Been idling like this for a long time.

Last edited by larry_c4; Oct 2, 2016 at 03:05 AM.

Oct 2, 2016 | 07:51 AM

aklim

Team Owner

Joined: Jul 2004

Posts: 28,432

Likes: 3,285

From: Hartford WI

Before you declare a problem, how about investigating if there is a problem first? What does the ECM see and not what the tach says. I have checked with the scanner and an inductive timing light with a tach. Both light and scanner agree. Car tach was inaccurate by 300 rpm

Also, what is the command idle speed? If that is set low, nothing you do can change it.