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I have a '91 1LE Z28 that is an original, un-molested low miles collector car that I don't drive very often. I'm the 3rd owner of the car and it only has 37,XXX miles on it. Today I decided to get it out and take it for a drive this morning to go get some breakfast. Drove it about 14 miles to where I was going and parked it. Went in, ate breakfast and then headed back home with it. I made it about 2 miles on the trip back and the motherfucker just quit running at highway speed. (Ask me if I was mad) Anyway, did some troubleshooting when I finally got it home (had it towed) and ruled out fuel and spark...and the VATS - albeit tentatively. I can't figure out wtf is wrong with it. Has great fuel pressure, I swapped out the ign. module...checked the VATS system and it seems to be working ok. (This car has a resistor key) It'll start and run just briefly and then it just stumbles and stalls. Occasionally it will make an initial stumble and then pick back up again, but then it'll stumble again and stall. It acts just like it runs out of fuel...like the injector pulse is stopping. If the VATS was malfunctioning I would expect a security light when it stalls but this is not the case. Any of you meatheads ever run across this issue in an older GM product before? The car has an LB9 TPI 305 in it.
 

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If it were a GTO throwing a P0601 code with those symptoms I'd tell you to reflash the PCM, BCM, & PIM, but since it's not I got nuthin.

I know this'll show up more as a starting problem than a running problem, but does it have enough fuel pressure?
 

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move the eff over
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If the Camaro is stupid, I'm a certified moron I guess. :)

Sounds like an electrical problem. Like something heating up and creating too much resistance. Does that thing have a single coil ? I'm old enough to remember those cars, but too old to recall what kind of ignition system they had, lol.
 

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Discussion Starter #7
If it were a GTO throwing a P0601 code with those symptoms I'd tell you to reflash the PCM, BCM, & PIM, but since it's not I got nuthin.

I know this'll show up more as a starting problem than a running problem, but does it have enough fuel pressure?
Fuel pressure is right on spec, supposed to be 41-47 psi, it's at 45 with 0 static leak off. It was running perfectly prior to today.

Running then not running? Fluxuates with rpm?

Sounds like vacuum leak. Can't help much more then that, I only go back to LTx motors.
Nope, there's no fluxuation - it won't fucking RUN.

If the Camaro is stupid, I'm a certified moron I guess. :)

Sounds like an electrical problem. Like something heating up and creating too much resistance. Does that thing have a single coil ? I'm old enough to remember those cars, but too old to recall what kind of ignition system they had, lol.
It has a single coil that is mounted on a bracket next to the distributor. The coil looks good...in my past experience you can always tell when a coil has failed - there's telltale signs. And, in all my years turnin wrenches and troubleshooting problems, I bet I have only come across maybe 3 failed coils in my lifetime. Its just not a common problem. I did swap out the ignition module with a known good one, same issue. I swear I think it has something to do with the VATS, but the indications wouldn't suggest it (judging by the behavior of the "security" light).

I'll figure it out sooner or later. If not I'll just drop a 454 in it with a giant Holley on it and hack all the wiring back with a big pair of toenail clippers - that's what everyone else does, right?
 

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The Entenmann's Shim-Sham
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Check the voltage output on the throttle position sensor? I'd also check the IAC.
 

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It could be VATS not reading the key. You can just get the ohm reading off your key and then solder the needed resistors inline under the dash. I forget what wire you splice the resistors into, but there are plenty of write-ups online. I did it on my cousin's 88 GTA when his wouldn't start and everything checked out mechanically. It fired right up after a quick trip to Radioshack.
 

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Discussion Starter #11

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Discussion Starter #12
It could be VATS not reading the key. You can just get the ohm reading off your key and then solder the needed resistors inline under the dash. I forget what wire you splice the resistors into, but there are plenty of write-ups online. I did it on my cousin's 88 GTA when his wouldn't start and everything checked out mechanically. It fired right up after a quick trip to Radioshack.
Well, according to the light on the dash there isn't an issue with the VATS system reading the key. If there were, the "security" light would come on when it stalled. That light is functioning like its supposed to. Furthermore, if it wasn't reading the key it wouldn't even allow me to engage the starter. I have checked the key, it's an 1870 ohm resistor key. I will admit though that I am still not 100% sure it's not related to VATS. It acts just like the injector pulse goes away when it quits running. Its not flooding at all and it always starts right up with subsequent tries, it just won't stay running.
 

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Discussion Starter #13
Also on my list of suspects is the magnetic pickup in the distributor. They will cause weird symptoms when they fail also.
 

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The Entenmann's Shim-Sham
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If I remember correctly, the security light never illuminated on my cousin's car when it was having issues with VATS, but he was unable to engage the starter at all when it wasn't reading the key.
 

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I had a similar issue in an 85 Cavalier with a throttle body. Problem ended up being a bad PCM. Dunno if that helps or not.
 

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Discussion Starter #16
If I remember correctly, the security light never illuminated on my cousin's car when it was having issues with VATS, but he was unable to engage the starter at all when it wasn't reading the key.
Yep, that is correct. If it is working properly you won't get anything when you turn the key. VATS is supposed to disable the starter solenoid relay, the ignition coil and the injector pulse on these cars.

I had a similar issue in an 85 Cavalier with a throttle body. Problem ended up being a bad PCM. Dunno if that helps or not.
VATS didn't start until '86 on the Corvette and followed in '87 on several other GM models. It very could be a bad ECM.
 

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I...I...I got Nothin
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With an '86 Trans Am, '82 Berlinetta, 86 IROC under my belt I can safely tell you that the entire computer module had to be replaced in all three cars...well, except for the Berlinetta Not much computer management on a carbureted V6.

The computer completely failed and an entirely new module had to be installed.
 

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Discussion Starter #18
I've probably owned more of these cars than most people in the country...and I never had to replace any ECMs. HOWEVER - it's been a very longtime ago that I owned most of em. lol...
 

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Possibly unrelated, but possibly related... Had the same issue many moons ago on my 1988 Chevy S10 Blazer with the 4.3L Vortec V6. One day it started running like ass, and cut out during driving. It would start, but sputter for a bit and stall. Trying to drive was a no go because it wouldn't stay running long enough. Tried taking it in a doing a full tune up (plugs, wires, ignition and fuel system checks, fuel/air filters, etc). Traced it back to a completely clogged catalytic converter. Replaced that with a brand new one, and the thing ran like a champ until I got rid of it.

I am no expert though. :dunno:
 

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1LE
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I don't think it's the VATS. We only had them cause a "no start" when the little white wires on the ignition cylinder finally snap, never caused a stall issue.

I think you are on the right track with the distributor pick up, and don't overlook the ECM. I've been told the solder on the old ECM's can start to deteriorate and cause issues.

If you didn't just drive it for 15 miles I would have thought gas quality since the car sits.


Once you have it running can you tell what stops?
I mean do you lose spark or injector?
It should be easy to tell you can see the injector/spray gumout to keep it running. Or does a spark tester stop firing as the engine dies. If you lose both I would look to the dist pick up.

But you probably know all this.


What's the ECM coolant sensor read? Failed sensor or wiring usually give you a -34° coolant reading and very rich fuel ration command.


Best of luck to you.
 
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