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Runs great, then stumbles & dies at random...??

Old 10-28-2006, 03:28 AM
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Runs great, then stumbles & dies at random...??

Any ideas here on what could be my issue?

I have a 92 Z28 that I just picked up a while back. My problem is strange.... I can start the car, drive around for a bit, then the tach starts jumping around, the engine runs terrible, then eventually dies and won;t restart for roughly 30 minutes. I am thinking the distributer is bad, but am unsure. I have just replaced the module in the distributer with a new one, new cap & rotor, new plugs and wires, etc... Does this sound like a dist. problem? I am lead to believe so for the simple fact that the tach goes crazy as soon as it starts running bad. This car runs GREAT until this issue..Like I said though, when it happens, it won't restart unless you let it set for about 30 or so minutes, then it fires right up and purs like a kitten again.

The timing is set at 6 degrees base, no modifications to the car that I am aware of... 108,000 on the odometer, no codes are being set, etc..

Any help would be greatly appreciated !

Jason
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Old 10-28-2006, 02:34 PM
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Car: '88 IROC-Z / '91 Z28 / '91 GTA
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I had something very similar.. the car would start to surge and stumble, then die... and not restart for about a half hour. Turned out to be a bad fuel pump with a very plugged screen. Replaced the fuel pump and assembly in the tank, ran like a champ after that.

Good luck.
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Old 10-28-2006, 03:13 PM
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had the same problem this summer, turned out to be a fule pump also
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Old 10-29-2006, 02:38 AM
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But the tach jumping is definitely an ignition problem. You might be burning a plug wire, if you've already covered the other problems. Or, could even be fuse, or even ECU related.

I would have suspected the ignition module firstly. Did you use the heat sink compound?

Might be pickup coil in the distributor, though. Do you have 2 cars now? Swap distributors and see.
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Old 10-29-2006, 03:04 PM
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Originally Posted by RednGold86Z View Post
But the tach jumping is definitely an ignition problem. You might be burning a plug wire, if you've already covered the other problems. Or, could even be fuse, or even ECU related.

I would have suspected the ignition module firstly. Did you use the heat sink compound?

Might be pickup coil in the distributor, though. Do you have 2 cars now? Swap distributors and see.


The tach leads me to believe it is ignition related too. I just got another distibuter for it yesterday and hope to get to it today. The module is new and I did use the gel stuff it came with. Wires are new, plugs, everything I can think of... hOPEFULLY THE DISTIBUTER CLEARS UP THE PROBLEM.

jASON
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Old 10-29-2006, 09:44 PM
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OK...I swapped out the distributer for another, seems better, but after idleing in the driveway for about 20 minutes, it sort of stumbled for about 10 seconds or so, then cleaned up and ran another 5 or so before doing it again. The tach is not jumping like before, but it still started running bad for a bit. Near the intake, it sounded like air being sucked in back by the rear of the engine while the rough running was occuring....checked for vaccum leaks by spraying carb cleaner all over around the intake and came up with nothing. Next thing I think I will try is hooking up a fuel pressure gauge and watching that...maybe it will fluctuate as it stumbles? I am not understanding this stinkin' car.

Another thing, when it stumbles, the exhaust fumes are pretty bad, also after revving the engine...

Jason
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Old 10-30-2006, 08:05 PM
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check your injectors with an ohm meter, warm should be around 14.5,12.5 is almost dead. mine were cool except two that ohmed at about 7.5 and 6. I believe bad injectors can make the car run rich and die out. my ......good luck...ps i also had a cap that wasnt on right and burnt wire that made it run rich and very bad.
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Old 10-30-2006, 08:49 PM
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Well...I was through with messing around with it and dropped it off at a buddys repair shop, it ran fine all day while hooked up to the scanner and after they put a new cat on it (old one was punched out), the car passed smog just fine. It does not run rich, just with no cat it smelled like it. The car actually runs a little on the lean side they said. Who knows, maybe it will be a good car now..?

Jason
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Old 11-01-2006, 09:37 AM
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You scared it.
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Old 11-01-2006, 01:43 PM
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Would the VSS also make the tach jump ? Sure the speedo does ...but they can mess with the cars ability to run .
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Old 11-01-2006, 06:17 PM
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OK...the car still does it, but now the tach does not jump around, only fluctuates as the RPM's do...It smells as though it is flooding out and smells as such when the problem occurs. I am going to check all of the vaccum hoses around the MAP sensor and replace the coolant sensor....The search goes on.


Jason
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Old 11-01-2006, 10:33 PM
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its gotta be a bad fuel pump i had this problem towards the end of last yr before i put it in away for winter and at the beginnig of this year....i had the exact same symptoms. last year i changeed 2 cats because it sounded like the car was stiffeling... rpms would jump and then the exhaust would smell funny so i changed the cat twice ,,,, this year i put all new plugs and a msd iginiton coil and fuel filter guess wut ........ same shet so i finally changed the fuel pump and bam all the problems stopped.....u need t ocheck fuel pressure but not wen shes idiling perfect wen she starts to stumble then u slap the gauge on an see wut psi shes at

Last edited by pearl_iroc; 11-01-2006 at 10:39 PM.
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Old 11-02-2006, 11:37 AM
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im not sure if youve got tpi or tbi , but maybe bad diphram on the regulator.
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Old 11-02-2006, 08:41 PM
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Changed out the MAP sensor last night, no problems today....did not drive too much, but more than normal..

I am hoping that was it.

Jason
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Old 12-23-2018, 02:49 AM
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Re: Runs great, then stumbles & dies at random...??

Originally Posted by ROCITUP View Post
im not sure if youve got tpi or tbi , but maybe bad diphram on the regulator.
hey my car is doing same thing but after i jiggles some wires by the bat it sometimes clears it up but then all of a sudden it will do it again it seems likes its running out of gas and tach is jumping up and down and no matter how much i rev it up it just goes blah and dies and then i try to start it and it starts but seems like its running on five cylindernders please help
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Old 12-23-2018, 04:45 AM
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Re: Runs great, then stumbles & dies at random...??

Originally Posted by D's89IROCZ View Post
Would the VSS also make the tach jump ? Sure the speedo does ...but they can mess with the cars ability to run .
what is the vss and is there a regulator on tbi models
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Old 12-25-2018, 11:44 AM
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Re: Runs great, then stumbles & dies at random...??

Originally Posted by Earl Wright View Post
what is the vss and is there a regulator on tbi models
vehicle speed sensor, if your asking about a fuel pressure regulator itís in the Throttlebody next to the injectors.
kinda a old thread maybe start a new one with your issues.
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