Random stall when coming to idle - ZR-1 Net Registry Forums

-=Jeff=- · 09-27-2021

So I have been fighting with a stalling issue. If I am coming to a stop, I usually put it in neutral and coast as I slow down. Every once in a while, the car will stall. Just drop out. It will restart and be fine, usually for the rest of the drive. Just not sure where to look next.

I have:
New O2 sensors
New injectors
New coils
New wires
Plugs are about a year old
New fuel filter
Phil's fuel regulator

I don't seem to have any vacuum leaks
Fuel pressure is solid

Outside of the stall when coming to idle the car runs great

Thoughts on where to look next?

wfot · 09-27-2021

possibly the idle control motor?
could been old
or could just be dirty.
John

BlackZR1 · 09-27-2021

What are your IAC counts at idle?
If you are much higher than 10 it suggests your throttle is closed too much and you are relying on the IAC to keep the car from stalling.(Yes the IAC regulates idle speed but the min. throttle hard stop setting should be high enough to keep the car running just below idle rpm target with 0 counts.)
I went through this last month and followed the procedure by XfireZ51 here:
http://zr1.net/forum/showthread.php?p=261060#post261060
Have not had a problem since.

-=Jeff=- · 09-27-2021

IAC was swapped with no change. I did the IAC procedure a couple times. I may need to go through it again but IAC counts are 10 or less fully warm (no AC)

WARP TEN · 09-28-2021

Jeff, you might check with Marc or stop in to see him. I had this stalling problem shortly after he did his 510 package on the '95 and as I recall he just made a minor adjustment to the throttle cable at the front of the engine. I may be wrong, as it was several eyars ago, but that is what I recall.--Bob

-=Jeff=- · 09-28-2021

Thanks Bob,

I have been chatting with him as well.. it happening less now.. time
Will tell

1991 Corvette ZR-1 · 09-28-2021

MAP line all clear? This was what stalled mine under the same conditions you?re describing.

-=Jeff=- · 09-28-2021

Quote:

Originally Posted by 1991 Corvette ZR-1

MAP line all clear? This was what stalled mine under the same conditions you?re describing.

Yes

Young1 · 09-28-2021

My car did than when the camshaft position sensor was bad. Check for codes. I think it is 31?

-=Jeff=- · 09-29-2021

Quote:

Originally Posted by Young1

My car did than when the camshaft position sensor was bad. Check for codes. I think it is 31?

Yeah no codes present. But interesting issue with cam sensor

09-27-2021	#1
-=Jeff=- Join Date: Jul 2007 Location: Bartlett, IL Posts: 7,164	Random stall when coming to idle So I have been fighting with a stalling issue. If I am coming to a stop, I usually put it in neutral and coast as I slow down. Every once in a while, the car will stall. Just drop out. It will restart and be fine, usually for the rest of the drive. Just not sure where to look next. I have: New O2 sensors New injectors New coils New wires Plugs are about a year old New fuel filter Phil's fuel regulator I don't seem to have any vacuum leaks Fuel pressure is solid Outside of the stall when coming to idle the car runs great Thoughts on where to look next? __________________ 1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Flowmaster Cats - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978

09-27-2021	#2
wfot Join Date: Jan 2009 Location: New jersey Posts: 156	Re: Random stall when coming to idle possibly the idle control motor? could been old or could just be dirty. John

09-27-2021	#3
BlackZR1 Join Date: Aug 2015 Location: Pittsburgh, PA Posts: 152	Re: Random stall when coming to idle What are your IAC counts at idle? If you are much higher than 10 it suggests your throttle is closed too much and you are relying on the IAC to keep the car from stalling.(Yes the IAC regulates idle speed but the min. throttle hard stop setting should be high enough to keep the car running just below idle rpm target with 0 counts.) I went through this last month and followed the procedure by XfireZ51 here: http://zr1.net/forum/showthread.php?p=261060#post261060 Have not had a problem since. __________________ Roger 1990 ZR-1 #2699 Black on Black 15,000 miles Full-time secondaries, 4.10 gears, C-beam plates, ported top end

09-27-2021	#4
-=Jeff=- Join Date: Jul 2007 Location: Bartlett, IL Posts: 7,164	Re: Random stall when coming to idle IAC was swapped with no change. I did the IAC procedure a couple times. I may need to go through it again but IAC counts are 10 or less fully warm (no AC) __________________ 1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Flowmaster Cats - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978

09-28-2021	#5
WARP TEN Join Date: Apr 2007 Location: Lake Bluff, IL Posts: 2,088	Re: Random stall when coming to idle Jeff, you might check with Marc or stop in to see him. I had this stalling problem shortly after he did his 510 package on the '95 and as I recall he just made a minor adjustment to the throttle cable at the front of the engine. I may be wrong, as it was several eyars ago, but that is what I recall.--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"

09-28-2021	#7
1991 Corvette ZR-1 Join Date: Sep 2018 Location: Florida Posts: 305	Re: Random stall when coming to idle MAP line all clear? This was what stalled mine under the same conditions you?re describing.

09-28-2021	#9
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 895	Re: Random stall when coming to idle My car did than when the camshaft position sensor was bad. Check for codes. I think it is 31? __________________ 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.