IAC Valve Maintenance, Symptom was Seemingly a Starvation of Fuel - ZR-1 Net Registry Forums

Blue Flame Restorations · 06-27-2012

Solved an issue today.

Started the car this morning and after about 15-30 seconds the idle began to rise to over 3k. I blipped the throttle and it did not come back down.

Background Info

My car ran very inconsistently shortly before Bowling Green in May and after I got home, a fuel pump failed. I installed CHEAP Airtx fuel pumps (I had them, so I used them)

When I would first drive the car in the morning, I'd get a stumble from 1st to 2nd gear when pulling out of the neighborhood. Yesterday, it almost died due to starving of fuel. After warming up, it runs OK but feels like it's starving for fuel, to an extent. I thought maybe one of the cheap fuel pumps was beginning to fail?

Today

After my high idle occurred, I checked the MAP hose and also the IAC connections. TPS was not loose. Shut off car and re-started. Idle was ok. Drove car and it still felt like it had a weak fuel condition from the pumps.

I loosened the IAC valve and began to clean it with solvent. Wahla! A large chunk of carbon fell out onto my hand. The chunk was about 1/4" or larger and it was also thick. I finished cleaning the IAC and the spring and also the hole in the plenum. Re-attached the IAC and started the car. Seemed to idle just fine. (be careful not to drop a screw underneath the plenum)

Drove the car. Exhaust note was nice and smooth and no more stumble.
Ripped a few gears and PERMAGRIN is back!

My Point

I'm slowly learninig the preventive maintenance of the LT5. It's a lot of enjoyment when you start to get the feel of the car and know how to diagnose issues as they come up.

Maybe this post will help someone inn the future???

Brett

A26B · 06-27-2012

Very good post Brett. Are you using K&N air filter?

Blue Flame Restorations · 06-27-2012

Quote:

Originally Posted by A26B

Very good post Brett. Are you using K&N air filter?

Hi Jerry. No, I have the SLP three fork system right now. I plan on changing it to the Copeland open unit soon though.

scottfab · 06-27-2012

FYI . Way back before the forum when there was only an email list the issue of IAC cleaning came up multiple times. The gist of the experts was not to clean the IAC too thoroughly. There is a special grease used on them that needs to stay (same grease used on the TB plates). Since that time whenever I've cleaned it (every 4yrs) I always clean just what I know to be carbon. The area in the crevices by the shaft I leave alone.
Each to his own though.
An important area to get is the "in" and the "out" to the IAC on the TB.

06-27-2012	#1
Blue Flame Restorations Join Date: Feb 2010 Location: Pendleton, IN Posts: 3,899	IAC Valve Maintenance, Symptom was Seemingly a Starvation of Fuel Solved an issue today. Started the car this morning and after about 15-30 seconds the idle began to rise to over 3k. I blipped the throttle and it did not come back down. Background Info My car ran very inconsistently shortly before Bowling Green in May and after I got home, a fuel pump failed. I installed CHEAP Airtx fuel pumps (I had them, so I used them) When I would first drive the car in the morning, I'd get a stumble from 1st to 2nd gear when pulling out of the neighborhood. Yesterday, it almost died due to starving of fuel. After warming up, it runs OK but feels like it's starving for fuel, to an extent. I thought maybe one of the cheap fuel pumps was beginning to fail? Today After my high idle occurred, I checked the MAP hose and also the IAC connections. TPS was not loose. Shut off car and re-started. Idle was ok. Drove car and it still felt like it had a weak fuel condition from the pumps. I loosened the IAC valve and began to clean it with solvent. Wahla! A large chunk of carbon fell out onto my hand. The chunk was about 1/4" or larger and it was also thick. I finished cleaning the IAC and the spring and also the hole in the plenum. Re-attached the IAC and started the car. Seemed to idle just fine. (be careful not to drop a screw underneath the plenum) Drove the car. Exhaust note was nice and smooth and no more stumble. Ripped a few gears and PERMAGRIN is back! My Point I'm slowly learninig the preventive maintenance of the LT5. It's a lot of enjoyment when you start to get the feel of the car and know how to diagnose issues as they come up. Maybe this post will help someone inn the future??? Brett __________________ 1988 KOH Prototype EX5023 sold 1990 ZR-1 #444 Convertible 1990 ZR-1 Black #966 1991 ZR-1 Quazar Blue #296 1957 Duntov SS Project Last edited by ZBrink; 3 Weeks Ago at 01:03 AM. Reason: edited for clarity

06-27-2012	#2
A26B Join Date: Dec 2003 Location: Arcadia, OK Posts: 3,392	Re: IAC Maintenance Very good post Brett. Are you using K&N air filter? __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.

06-27-2012	#4
scottfab Join Date: Jan 2009 Location: Portland Oregon metro area (Washington side) Posts: 3,193	Re: IAC Maintenance FYI . Way back before the forum when there was only an email list the issue of IAC cleaning came up multiple times. The gist of the experts was not to clean the IAC too thoroughly. There is a special grease used on them that needs to stay (same grease used on the TB plates). Since that time whenever I've cleaned it (every 4yrs) I always clean just what I know to be carbon. The area in the crevices by the shaft I leave alone. Each to his own though. An important area to get is the "in" and the "out" to the IAC on the TB. __________________ Scott Vett owner since 1979._It's about the car and the people

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode