First Post From a Long Time Z31 Owner...Engine Won't Stay Running
11-11-2012, 08:43 AM
#1
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Join Date: Nov 2012
Posts: 8
First Post From a Long Time Z31 Owner...Engine Won't Stay Running
Hi Everyone,
I've had my Z for what seems like a million years and used the old Z31.com for guidance when I rebuilt my 87NA hardtop's engine in like 2000. My car was even in the corners of the pages of Z magazine...remember that one?!
Anyway, I have never had an engine starting problem that I couldn't figure out until now. A few months ago, I drove on a short trip and parked...no problem. When I came back, it started but once I stepped on the gas, it died. Every time I crank it, it will start momentarily, and then die. If I touch the gas, it dies. But, when it runs, it sounds fine.
I towed it back home, and I haven't had the time to dig into it until now. It has a new battery and I ran a charger to make sure it was fully charged. I get spark at least to #4 because I watched the spark jump to the plenum when I laid it on there. I cleaned the CAS but I didn't notice anything. I put in a new coil but still no help. I cleaned the distributor parts just in case.
The first start of the morning, the car will run for 30-40 seconds before dying. There is new gas in the tank and without testing the actual pressure, I get a fountain of gas from my line when the pump kicks on. I even bypassed the fuel filter in case that was the problem, but no joy. Once I get the letdown after that first nice start, it won't run for more than a few seconds.
When I checked the ECU in mode 3, it only threw the code for the fuel temperature sensor. I don't think that would make it stall like this. The regulator is fine...the diaphragm is not compromised. The PCV was fine. I sprayed contact cleaner on anything I could see but aside from the wires being brittle (what do you want from a 25 year old car), nothing caught my eye. There does not seem to be any post-MAF leaking so I am left thinking that it is the CHTS.
Anyone else have any ideas for me before I go crazy? I am going to check the negative terminal of the battery to be sure it's connected and grounded but aside from that...I am open to anything you have for me. I do not want to buy sensors I do not need so hopefully someone has some insight.
Thanks a bunch and I'm glad I found a new forum!
I've had my Z for what seems like a million years and used the old Z31.com for guidance when I rebuilt my 87NA hardtop's engine in like 2000. My car was even in the corners of the pages of Z magazine...remember that one?!
Anyway, I have never had an engine starting problem that I couldn't figure out until now. A few months ago, I drove on a short trip and parked...no problem. When I came back, it started but once I stepped on the gas, it died. Every time I crank it, it will start momentarily, and then die. If I touch the gas, it dies. But, when it runs, it sounds fine.
I towed it back home, and I haven't had the time to dig into it until now. It has a new battery and I ran a charger to make sure it was fully charged. I get spark at least to #4 because I watched the spark jump to the plenum when I laid it on there. I cleaned the CAS but I didn't notice anything. I put in a new coil but still no help. I cleaned the distributor parts just in case.
The first start of the morning, the car will run for 30-40 seconds before dying. There is new gas in the tank and without testing the actual pressure, I get a fountain of gas from my line when the pump kicks on. I even bypassed the fuel filter in case that was the problem, but no joy. Once I get the letdown after that first nice start, it won't run for more than a few seconds.
When I checked the ECU in mode 3, it only threw the code for the fuel temperature sensor. I don't think that would make it stall like this. The regulator is fine...the diaphragm is not compromised. The PCV was fine. I sprayed contact cleaner on anything I could see but aside from the wires being brittle (what do you want from a 25 year old car), nothing caught my eye. There does not seem to be any post-MAF leaking so I am left thinking that it is the CHTS.
Anyone else have any ideas for me before I go crazy? I am going to check the negative terminal of the battery to be sure it's connected and grounded but aside from that...I am open to anything you have for me. I do not want to buy sensors I do not need so hopefully someone has some insight.
Thanks a bunch and I'm glad I found a new forum!
11-11-2012, 10:03 AM
#2
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Join Date: Nov 2012
Posts: 8
I checked and cleaned the fuse panel...
and looked in the trunk to make sure the fuel pump is ok. I have not checked voltage back there yet but I'll get to it. I'm beginning to think it's the fuel pressure regulator. Could that make this start and die so fast? 
11-11-2012, 03:11 PM
#3
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Join Date: Nov 2012
Posts: 8
More info...
Later this afternoon, I took off the intake post MAF and disconnected the lines going into it so I could clean out the butterfly. It started right up...and ran understandably rough. If I block the vacuum hoses that should have been attached to the intake, it dies again. That at least tells me that fuel pressure is not an issue and neither is anything related to ignition such as CAS and such.
The idle-up solenoid (I have an NA) had corroded wires leading up to the valves so I removed it, cleaned out the port that extends into the intake manifold and soldered the wires back together...all that could do short of buy a new one which certainly isn't possible on a Sunday afternoon.
When all was said and done, it didn't matter if the idle up solenoid harness was connected or not...it still ran. if the hose attaching the solenoid to the intake was not connected, the car ran. When it was connected, the car would not start or stay running. SO, even though it never threw a code, I'm thinking it is the MAF since the only way it will run is it I introduce air PAST the MAF but since it can't be metered for, as I increase the throttle, the car dies because it can't properly change the mixture because the MAF does not sense the increase in air coming into the intake.
C'mon...what do you think? I haven't pulled the MAF to meter it to see if it's bad but I think I'll grab one online just in case.
The idle-up solenoid (I have an NA) had corroded wires leading up to the valves so I removed it, cleaned out the port that extends into the intake manifold and soldered the wires back together...all that could do short of buy a new one which certainly isn't possible on a Sunday afternoon.
When all was said and done, it didn't matter if the idle up solenoid harness was connected or not...it still ran. if the hose attaching the solenoid to the intake was not connected, the car ran. When it was connected, the car would not start or stay running. SO, even though it never threw a code, I'm thinking it is the MAF since the only way it will run is it I introduce air PAST the MAF but since it can't be metered for, as I increase the throttle, the car dies because it can't properly change the mixture because the MAF does not sense the increase in air coming into the intake.
C'mon...what do you think? I haven't pulled the MAF to meter it to see if it's bad but I think I'll grab one online just in case.
02-08-2013, 09:50 PM
#9
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Join Date: Dec 2012
Location: The Emerald City from the Wizard of Oz! Dope it out.
Posts: 8
I just went through the exact same problem Even had a MAF code on the ECU. I chose to not believe it. I found a busted hose on the idle up solenoid. Since it is on the down stream side of the MAF, The idle up solenoid was sucking atmos. The ECU was getting wrong info about how much air was entering the throttle body and therefore sending bad info about how much fuel to pump. Temp fix on the hose, I can't find a real idle up solenoid hose for my 85 na z31, and it runs great again.
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