High searching Idle - ZR-1 Net Registry Forums

jss06c6 · 02-09-2018

Well, just moved #473.. drove it two weeks ago, no issues, ran beautifully. When I started it to move it today, the car sounded like it backfired immediately upon start. But shut down instantly. I cranked it again and it started right up. Took it out for a spin around the block and it ran great, BUT, the idle is now at 1250, not 750 like it is supposed to be.

Pulled into shop and looked around the engine. The PCV plug at the back of the engine was partially popped off. Likely due to the backfire. Pushed it back down and the idle dropped to 1150.

Pulled the IAC and it was clean. Put it back in and hooked up Moates interface and launched TunerPro RT. Started the engine and the IAC is locked at 0. Engine is hunting for idle. My guess is that the IAC cratered.

Input welcomed. Any way to check the IAC before I look for a new one?

Are these IAC's available still? Jerry, do you have one for a '91?

Thanks Guys...

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secondchance · 02-09-2018

I would check MAP sensor vacuum line (unless when you said PCV line partially popped off, you meant MAP sensor vacuum line).

jss06c6 · 02-09-2018

Map sensor line is good. The double PCV plug was not fully seated on the PCV valves..

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XfireZ51 · 02-09-2018

Quote:

Originally Posted by jss06c6

Map sensor line is good. The double PCV plug was not fully seated on the PCV valves..

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Have u tie wrapped it down?

jss06c6 · 02-09-2018

Dominic, it's very tight. I'll check again. When I lost the MAP hose connection about 18 months ago, the car wouldn't hold an idle and was almost undrivable. The car drives beautifully, but now has high idle and it "hunts" about 100 rpm up and down..

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jss06c6 · 02-09-2018

It's possible the backfield pushed another vacuum hose loose under the plenum. If it is indeed a vacuum leak, it's a very slight one..

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XfireZ51 · 02-09-2018

Just about every vacuum connection on my motor is tie wrapped. I hate vacuum leaks no matter how slight.
When I got my first ZR, it ran great but had a slight hunt. Marc looked at it and said PCV. He was right.

jss06c6 · 02-09-2018

Ok, will tie wrap the PCV connection.. I've got a new one too, might just change it out..

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jss06c6 · 02-09-2018

Not sure what I can try wrap.. hose clamps on all single pipe connections. I'll put the new o e on and see if that resolves it.[ATTACH][ATTACH]

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XfireZ51 · 02-09-2018

Tie wrap the top and bottom halves of the F to each other.

02-09-2018	#1
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	High searching Idle Well, just moved #473.. drove it two weeks ago, no issues, ran beautifully. When I started it to move it today, the car sounded like it backfired immediately upon start. But shut down instantly. I cranked it again and it started right up. Took it out for a spin around the block and it ran great, BUT, the idle is now at 1250, not 750 like it is supposed to be. Pulled into shop and looked around the engine. The PCV plug at the back of the engine was partially popped off. Likely due to the backfire. Pushed it back down and the idle dropped to 1150. Pulled the IAC and it was clean. Put it back in and hooked up Moates interface and launched TunerPro RT. Started the engine and the IAC is locked at 0. Engine is hunting for idle. My guess is that the IAC cratered. Input welcomed. Any way to check the IAC before I look for a new one? Are these IAC's available still? Jerry, do you have one for a '91? Thanks Guys... Sent from my XT1585 using ZR-1 Net Registry mobile app Last edited by jss06c6; 02-09-2018 at 07:50 PM.

02-09-2018	#2
secondchance Join Date: Aug 2006 Location: McLean, VA Posts: 3,721	Re: High searching Idle I would check MAP sensor vacuum line (unless when you said PCV line partially popped off, you meant MAP sensor vacuum line).

02-09-2018	#3
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: High searching Idle Map sensor line is good. The double PCV plug was not fully seated on the PCV valves.. Sent from my XT1585 using ZR-1 Net Registry mobile app

02-09-2018	#5
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: High searching Idle Dominic, it's very tight. I'll check again. When I lost the MAP hose connection about 18 months ago, the car wouldn't hold an idle and was almost undrivable. The car drives beautifully, but now has high idle and it "hunts" about 100 rpm up and down.. Sent from my XT1585 using ZR-1 Net Registry mobile app

02-09-2018	#6
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: High searching Idle It's possible the backfield pushed another vacuum hose loose under the plenum. If it is indeed a vacuum leak, it's a very slight one.. Sent from my XT1585 using ZR-1 Net Registry mobile app

02-09-2018	#7
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,704	Re: High searching Idle Just about every vacuum connection on my motor is tie wrapped. I hate vacuum leaks no matter how slight. When I got my first ZR, it ran great but had a slight hunt. Marc looked at it and said PCV. He was right. __________________ [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

02-09-2018	#8
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: High searching Idle Ok, will tie wrap the PCV connection.. I've got a new one too, might just change it out.. Sent from my XT1585 using ZR-1 Net Registry mobile app

02-09-2018	#10
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,704	Re: High searching Idle Tie wrap the top and bottom halves of the F to each other. __________________ [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