Stalling sometimes at stops? - ZR-1 Net Registry Forums

rufcar · 12-02-2023

Recently on occasion my 90 zr1 stalls when rolling to a stop. On even rarer occasions it will throttle. On my old 89 bentley it was the idle control valve. Is that what's doing it on my 90? If so where is it located? Tkx jim f

-=Jeff=- · 12-03-2023

What are you doing in the rolling stop? Meaning are you slowing off brakes and motor? Or clutch in and it is neutral?

Have you put a scanner on it to see what it is doing? Specifically IAC steps and fuel.

Also what PROM is in the car?

I just went through this on my car, someone befor me modified some tables and that caused issues, I but that is one of many things

WARP TEN · 12-03-2023

This happened a bit after Marc did his 510 package on my '95. I stopped by his shop and he made a slight adjustment to (I think) the throttle stop and it was fine after that. My recollection made not be entirely accurate, as it was about 8 or 9 years ago, so I would suggest a call or email to him to see what he recommends. --Bob

XfireZ51 · 12-04-2023

Marc probably closed the throttle plates slightly to increase IAC steps.

rufcar · 12-04-2023

One of the previous owners had Marc do.many things and it's been fine the last 20k +/- mi. So this is new .it started after the 1st 1k mi I drove it. The only electronic item I did was clean the grounds and codes for the frame sensors.
Again can it possibly be the throttle control valve if I have one? Tkx jim

WARP TEN · 12-05-2023

Quote:

Originally Posted by XfireZ51

Marc probably closed the throttle plates slightly to increase IAC steps.

Entirely possible Dom--I just can't remember exactly what he did. --Bob

XfireZ51 · 12-05-2023

Well I guess we can ask Marc next week. Closing the throttle plates causes the ECM to increase IAC steps in order to maintain commanded idle speed. This gives the ECM more ?headroom? to control idle speed.

WydGlydJim · 12-05-2023

One thing to give a quick check to, is these PCV vacuum blocks common to the '90.....depending on the mileage, they can become oil soaked, and then not seal very well.....they are at the driver's side front of the plenum kind of tucked up in opening a bit......push on them a bit, and if they leak a lot, they should be replaced. They can cause erratic idle due to vacuum leak.

rufcar · 12-06-2023

Spoke to Hibeck today. Thinks it might be a semi stuck throttle. Just document it if and when it happens.

XfireZ51 · 12-06-2023

Had that issue w mine a number of years ago. I have a 63mm TB so no dag. Throttle return springs get weak after 30 years and I gotnone of Marc?s helper springs. Throttle closes correctly ever since.

12-02-2023	#1
rufcar Join Date: Mar 2023 Location: PA Posts: 47	Stalling sometimes at stops? Recently on occasion my 90 zr1 stalls when rolling to a stop. On even rarer occasions it will throttle. On my old 89 bentley it was the idle control valve. Is that what's doing it on my 90? If so where is it located? Tkx jim f

12-03-2023	#2
-=Jeff=- Join Date: Jul 2007 Location: Bartlett, IL Posts: 7,131	Re: Stalling sometimes at stops? What are you doing in the rolling stop? Meaning are you slowing off brakes and motor? Or clutch in and it is neutral? Have you put a scanner on it to see what it is doing? Specifically IAC steps and fuel. Also what PROM is in the car? I just went through this on my car, someone befor me modified some tables and that caused issues, I but that is one of many things __________________ 1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - 3" Magnaflow Bullet cats - LT4 Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978

12-03-2023	#3
WARP TEN Join Date: Apr 2007 Location: Lake Bluff, IL Posts: 2,030	Re: Stalling sometimes at stops? This happened a bit after Marc did his 510 package on my '95. I stopped by his shop and he made a slight adjustment to (I think) the throttle stop and it was fine after that. My recollection made not be entirely accurate, as it was about 8 or 9 years ago, so I would suggest a call or email to him to see what he recommends. --Bob __________________ 2016 Long Beach Red Z06 #10281 "POPS Z" 1995 Polo Green #409 "WARP TEN"--Haibeck 350/510 package, 4.10s, Hurst, Stock Exhaust with QTP Cutouts --Sold but still running strong 1993 Quasar Blue #161 "HIL KING" --Sold but still running strong, now with more than 120,000 miles 1967 Marlboro Maroon/Saddle Corvette Coupe 300 hp/4-spd --Sold a long time ago ZR-1 Net Registry Founding Member #95 NCM Lifetime Member Favorite Quote--Attributed to Mickey Thompson: "Too Much Horsepower is Almost Enough"

12-04-2023	#4
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,661	Re: Stalling sometimes at stops? Marc probably closed the throttle plates slightly to increase IAC steps. __________________ [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

12-04-2023	#5
rufcar Join Date: Mar 2023 Location: PA Posts: 47	Re: Stalling sometimes at stops? One of the previous owners had Marc do.many things and it's been fine the last 20k +/- mi. So this is new .it started after the 1st 1k mi I drove it. The only electronic item I did was clean the grounds and codes for the frame sensors. Again can it possibly be the throttle control valve if I have one? Tkx jim

12-05-2023	#7
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,661	Re: Stalling sometimes at stop Well I guess we can ask Marc next week. Closing the throttle plates causes the ECM to increase IAC steps in order to maintain commanded idle speed. This gives the ECM more ?headroom? to control idle speed. __________________ [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

12-05-2023	#8
WydGlydJim Join Date: Jan 2008 Location: Wichita, Ks. Posts: 317	Re: Stalling sometimes at stops? One thing to give a quick check to, is these PCV vacuum blocks common to the '90.....depending on the mileage, they can become oil soaked, and then not seal very well.....they are at the driver's side front of the plenum kind of tucked up in opening a bit......push on them a bit, and if they leak a lot, they should be replaced. They can cause erratic idle due to vacuum leak. __________________ 2009 LS9 1990 LT-5/sold/Bought my Baby back 1994 Lingenfelter LT-5/sold 1973 LS4/sold

12-06-2023	#9
rufcar Join Date: Mar 2023 Location: PA Posts: 47	Re: Stalling sometimes at stops? Spoke to Hibeck today. Thinks it might be a semi stuck throttle. Just document it if and when it happens.

12-06-2023	#10
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,661	Re: Stalling sometimes at stops? Had that issue w mine a number of years ago. I have a 63mm TB so no dag. Throttle return springs get weak after 30 years and I gotnone of Marc?s helper springs. Throttle closes correctly ever 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