92 Z NIGHTMARE - ZR-1 Net Registry Forums

Vettetech1 · 07-19-2013

Ok so I started this in the knock sensor holding you back thread and decided to start a new one. After replacing some injectors the car ran great. It sat a few weeks and the customer picked it up and said it was running worse then when he brought it to us. So after the weekend i came back in to see this black beast staring at me. I go and drive it and sure as hell its running like it did before i did the injectors. So i pull the plenum per my boss and recheck the injectors all ohm good none leaking all spraying. Put the plenum back on it and go to start it, Nothing. Found the starter had crapped out. So off the plenum comes again 3rd time in 3 weeks, get down to the starter and low and behold, a mouse created a home. Plugged the drain chewed on the purple starter wire and managed to kill the starter with his lil rat bladder. Got the starter in put the car back together (which im getting pretty good at if i dont say so myself). Hit the key it fires up, running nice and smooth, sweet thought i fixed it. NO (car god smacks me in the face). Pretty sure I got it down to a ignition miss, anybody have any tricks to finding a miss? Pulled plugs all look good like its running great. Regapped and reinstalled but the miss is still there. If anybody has any suggestions or ideas I'm all ears.
Car is a 92 with 24000 on the clock OEM AC Delco plugs, driven not beaten.

Schrade · 07-19-2013

No codes? No Closed Loop codes?

Short of that, can you post a datalog scan?

Jim Nolan · 07-19-2013

If I saw a mouse had made a home under the plenum I would have checked all the wiring and the plug wires. Those buggers are noted for chewing through wiring shields to make their nest. It maybe grounding out from a bare wire. 24k tells me it sits a lot even if an garage the mice can get to it, personal experience.

Vettetech1 · 07-19-2013

No codes, seems to be going through o2 loops like it should. Yeah checked all wiring didn't find anything but the starter wire chewed on. Found moister in cylinder 8 plug well dried it up, seemed to take care of the miss. Now its got a hesitation sag when you jump on it. both in neutral and when driving down the road. If you ease through the throttle seems to be OK. Something to ponder through the weekend its almost 4 and 100+ in the shop i am out for the day. Thanks for your thoughts and suggestions not real familiar with the LT5's.

XfireZ51 · 07-19-2013

Did you say you checked the fuel system? Pumps, strainers, fuel filter by passenger front?

LGAFF · 07-19-2013

2ndry map sensor under the ECM?

verify secondaries are opening, you can see them inside the plenum.....

Schrade · 07-19-2013

Quote:

Originally Posted by Vettetech1

No codes, seems to be going through o2 loops like it should. Yeah checked all wiring didn't find anything but the starter wire chewed on. Found moister in cylinder 8 plug well dried it up, seemed to take care of the miss. Now its got a hesitation sag when you jump on it. both in neutral and when driving down the road. If you ease through the throttle seems to be OK. Something to ponder through the weekend its almost 4 and 100+ in the shop i am out for the day. Thanks for your thoughts and suggestions not real familiar with the LT5's.

I think that idle quality and idle parameters will tell more about the tune, than road /engine response...

Could be wrong tho'.

rhipsher · 07-19-2013

This is what I'd do if my Z started to act up like the above described. I'd force it to throw an SES which in turn will store a code. If its stumbling when you get on it than you need to really get on it. I can almost assure you that when you hit somewhere around 7k the SES light will appear in the information center and will turn off when you back off of the throttle. And there's your code. I was also going to suggest checking to see if your MAP sensor hose is plugged in. It sounds like a stupid thing to overlook but I think we've all done it at one time or another. That will cause terrible idle and run like crap. Once it's plugged back in it will purr like a kitten. But the code will tell you where to look.

Blue Flame Restorations · 07-19-2013

I had an intermittemt miss that turned out to be a weak fuel pump. replaced both pumps and problem went away.

You need codes to appear

Vettetech1 · 07-20-2013

I had a knock code throw at one point. That's what brought me to this forum. But I haven't been able to get it to come back. The vacuum hose to the map sensor on the back of the plenum is new. The only worry spot I just thought about is the elbow that connects the two Pcv valves to the vacuum tube. Come to think about it they seemed pretty sloppy, it's got hose clamps on the bottom side. Any way to seal the top better without buying a new elbow. That could be part of the off idle stumble/hesitation. Been a long hot week maybe next week on a fresh brain will help. I'm sure it's something dumb.

07-19-2013	#1
Vettetech1 Join Date: Jul 2013 Location: Toledo Posts: 17	92 Z NIGHTMARE Ok so I started this in the knock sensor holding you back thread and decided to start a new one. After replacing some injectors the car ran great. It sat a few weeks and the customer picked it up and said it was running worse then when he brought it to us. So after the weekend i came back in to see this black beast staring at me. I go and drive it and sure as hell its running like it did before i did the injectors. So i pull the plenum per my boss and recheck the injectors all ohm good none leaking all spraying. Put the plenum back on it and go to start it, Nothing. Found the starter had crapped out. So off the plenum comes again 3rd time in 3 weeks, get down to the starter and low and behold, a mouse created a home. Plugged the drain chewed on the purple starter wire and managed to kill the starter with his lil rat bladder. Got the starter in put the car back together (which im getting pretty good at if i dont say so myself). Hit the key it fires up, running nice and smooth, sweet thought i fixed it. NO (car god smacks me in the face). Pretty sure I got it down to a ignition miss, anybody have any tricks to finding a miss? Pulled plugs all look good like its running great. Regapped and reinstalled but the miss is still there. If anybody has any suggestions or ideas I'm all ears. Car is a 92 with 24000 on the clock OEM AC Delco plugs, driven not beaten.

07-19-2013	#2
Schrade Join Date: Dec 2012 Location: NC Posts: 1,786	Re: 92 Z NIGHTMARE No codes? No Closed Loop codes? Short of that, can you post a datalog scan? __________________ I'm getting my snappics / threads removed blindly as fast as I can, to get in compliance with copyright / license TOS on the boards here (lots of FSM pages and other copyright / license violations on my part; sorry guys). And thanks to all the guys who didn't whine when I posted those FSM copyrighted / licensed stuff in my threads... ( :thumbsup: [b]and to think I complied with a mod's request to delete a pic of him in a Challenge Car in NCM Museum, so he wouldn't get in hot water)[/b] Thanks to several guys here for sending parts FREE; BearlyFlying, WeGone, Geezer, GoldCylon, and more there, TonyD, mike100, fletchusmc... 1990 #2794; 4L60e Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless, Power Effects 3" [IMG]https://lh5.googleusercontent.com/-GHpfzty7DVU/UQn-0Ru2xAI/AAAAAAAAA14/08mz1p4QLD4/s445/Screenshot-5.png[/IMG]

07-19-2013	#3
Jim Nolan Join Date: Jan 2007 Location: Florida Posts: 241	Re: 92 Z NIGHTMARE If I saw a mouse had made a home under the plenum I would have checked all the wiring and the plug wires. Those buggers are noted for chewing through wiring shields to make their nest. It maybe grounding out from a bare wire. 24k tells me it sits a lot even if an garage the mice can get to it, personal experience.

07-19-2013	#4
Vettetech1 Join Date: Jul 2013 Location: Toledo Posts: 17	Re: 92 Z NIGHTMARE No codes, seems to be going through o2 loops like it should. Yeah checked all wiring didn't find anything but the starter wire chewed on. Found moister in cylinder 8 plug well dried it up, seemed to take care of the miss. Now its got a hesitation sag when you jump on it. both in neutral and when driving down the road. If you ease through the throttle seems to be OK. Something to ponder through the weekend its almost 4 and 100+ in the shop i am out for the day. Thanks for your thoughts and suggestions not real familiar with the LT5's.

07-19-2013	#5
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,704	Re: 92 Z NIGHTMARE Did you say you checked the fuel system? Pumps, strainers, fuel filter by passenger front? __________________ [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

07-19-2013	#6
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,193	Re: 92 Z NIGHTMARE 2ndry map sensor under the ECM? verify secondaries are opening, you can see them inside the plenum..... __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359

07-19-2013	#8
rhipsher Join Date: Aug 2008 Location: Houston 90 Red ZR-1 Posts: 2,320	Re: 92 Z NIGHTMARE This is what I'd do if my Z started to act up like the above described. I'd force it to throw an SES which in turn will store a code. If its stumbling when you get on it than you need to really get on it. I can almost assure you that when you hit somewhere around 7k the SES light will appear in the information center and will turn off when you back off of the throttle. And there's your code. I was also going to suggest checking to see if your MAP sensor hose is plugged in. It sounds like a stupid thing to overlook but I think we've all done it at one time or another. That will cause terrible idle and run like crap. Once it's plugged back in it will purr like a kitten. But the code will tell you where to look.

07-19-2013	#9
Blue Flame Restorations Join Date: Feb 2010 Location: Pendleton, IN Posts: 3,904	Re: 92 Z NIGHTMARE I had an intermittemt miss that turned out to be a weak fuel pump. replaced both pumps and problem went away. You need codes to appear __________________ 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

07-20-2013	#10
Vettetech1 Join Date: Jul 2013 Location: Toledo Posts: 17	Re: 92 Z NIGHTMARE I had a knock code throw at one point. That's what brought me to this forum. But I haven't been able to get it to come back. The vacuum hose to the map sensor on the back of the plenum is new. The only worry spot I just thought about is the elbow that connects the two Pcv valves to the vacuum tube. Come to think about it they seemed pretty sloppy, it's got hose clamps on the bottom side. Any way to seal the top better without buying a new elbow. That could be part of the off idle stumble/hesitation. Been a long hot week maybe next week on a fresh brain will help. I'm sure it's something dumb.