High idle - ZR-1 Net Registry Forums

efnfast · 2 Weeks Ago

Sometimes my idle gets stuck north of 2,000 rpm. It doesn't seem to be throttle related, as in the cable or plates.
The only way to get it to come back down is pull over, come to a complete stop and wait a bit. Less than a minute.
Thoughts?

Young1 · 1 Week Ago

Buy throttle body cleaner spray. Remove accordion. Spray clean all well. Especially the little plate. Remove aluminum cover over cable. Spray all the mechanism with spray. First idea is grime because you have a higher mileage car.

efnfast · 1 Week Ago

I'll try that Steve, but it doesn't seem to be plate or cable related. If it was, I should be able to "tap" it down, or I could push in the clutch at speed and let it come down. It won't. The only way to get it to come down is bring the car to 0 mph. It feels like it's tune related.

tccrab · 1 Week Ago

My '90 does something similar, but not as extreme.
Approaching a stop the idle is around 1400rpm, once stopped for a few seconds the idle drops to 800ish.
Ive always believed it was smog related and allowing the cats to stay hot on deceleration.

Crabs

XfireZ51 · 1 Week Ago

I had that issue some years ago. My TB is bored to 63mm. I ended up buying Marc?s ?helper spring?. After all these years the return spring loses some of its closing power. Haven?t had that issue since.

efnfast · 1 Week Ago

It doesn't feel mechanical. I can coast down the highway with the clutch in for miles and the idle will never come down. Not until I come to a complete stop will it self correct.

Young1 · 1 Week Ago

Quote from service manual

Incorrect minimum idle speed may be caused by foreign material accumulation in the throttle, bore caulking, on the throttle valve, or on the throttle shaft.

Also a little research indicates to remove the IAC idle air control on the passenger side of the Plenum. It?s round with two small flanges, remove it, clean it and clean the passages in the plenum.

Hope this helps for your high miler

Mystic ZR-1 · 1 Week Ago

Quote:

Originally Posted by Young1

Quote from service manual

Incorrect minimum idle speed may be caused by foreign material accumulation in the throttle, bore caulking, on the throttle valve, or on the throttle shaft.

Also a little research indicates to remove the IAC idle air control on the passenger side of the Plenum. It?s round with two small flanges, remove it, clean it and clean the passages in the plenum.

Hope this helps for your high miler

I do that every couple of driving seasons, never had an idling problem.
You'd be suprised how much stuff is on it.

2 Weeks Ago	#1
efnfast Join Date: Nov 2011 Location: Dunbarton NH Posts: 7,270	High idle Sometimes my idle gets stuck north of 2,000 rpm. It doesn't seem to be throttle related, as in the cable or plates. The only way to get it to come back down is pull over, come to a complete stop and wait a bit. Less than a minute. Thoughts?

1 Week Ago	#2
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 879	Re: High idle Buy throttle body cleaner spray. Remove accordion. Spray clean all well. Especially the little plate. Remove aluminum cover over cable. Spray all the mechanism with spray. First idea is grime because you have a higher mileage car. __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

1 Week Ago	#3
efnfast Join Date: Nov 2011 Location: Dunbarton NH Posts: 7,270	Re: High idle I'll try that Steve, but it doesn't seem to be plate or cable related. If it was, I should be able to "tap" it down, or I could push in the clutch at speed and let it come down. It won't. The only way to get it to come down is bring the car to 0 mph. It feels like it's tune related.

1 Week Ago	#4
tccrab Join Date: Oct 2004 Location: Folsom CA Posts: 1,645	Re: High idle My '90 does something similar, but not as extreme. Approaching a stop the idle is around 1400rpm, once stopped for a few seconds the idle drops to 800ish. Ive always believed it was smog related and allowing the cats to stay hot on deceleration. Crabs __________________ TomC '90ZR1 #792 Honorary Pirate [B]If it ain't FUN, you're doing something terribly WRONG. [/B]

1 Week Ago	#5
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,669	Re: High idle I had that issue some years ago. My TB is bored to 63mm. I ended up buying Marc?s ?helper spring?. After all these years the return spring loses some of its closing power. Haven?t had that issue since. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

1 Week Ago	#6
efnfast Join Date: Nov 2011 Location: Dunbarton NH Posts: 7,270	Re: High idle It doesn't feel mechanical. I can coast down the highway with the clutch in for miles and the idle will never come down. Not until I come to a complete stop will it self correct.

1 Week Ago	#7
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 879	Re: High idle Quote from service manual Incorrect minimum idle speed may be caused by foreign material accumulation in the throttle, bore caulking, on the throttle valve, or on the throttle shaft. Also a little research indicates to remove the IAC idle air control on the passenger side of the Plenum. It?s round with two small flanges, remove it, clean it and clean the passages in the plenum. Hope this helps for your high miler __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.