Car runs, then stalls

hulakai

Registered User
1992 Auto, sat for the winter, was running when parked. Now when I start it cold, it will run fine for a few minutes then die and won't restart until it's cold again.

Yesterday I connected a scanner and did the KOER and cylinder balance tests. Passed everything. I mention the cylinder balance test because of this:

The scanner wants the car to run at 2000 rpm for two minutes before starting the KOER test. I was afraid it wouldn't run long enough for this but it did. So the scanner took over and ran all the tests with failures including the WOT throttle test. THEN I ran the cylinder balance test for the heck of it which takes another minute or two. It was the longest I had seen the car run since last year, about 5 minutes or more total I'd say, BUT as soon as I exited out of the program on the scanner, the engine died. It was almost as if the scanner had been controlling the ECU for the entire test and when it disconnected the ECU couldn't run the engine by itself.

So I'm suspecting the ECU...bad capacitors or whatever after 26 years and so it's just crashing when it warms up, therefore no codes.

Anyone agree/disagree or seen this before? The car is mint otherwise and has never been messed with under the hood. I wondered about the DIS but wouldn't there be a code in the ECU if that was causing the stall/no start?

Any help is much appreciated

Kevin

p.s. I have a working ECU from an 89 XR7 Auto. I'm sure the programming for a 1992 is a little different, but would that ECU work well enough in my 92 to prove/disprove my theory?
 
I'd first look at the sensors that come on line when the ECU goes closed loop; sounds like one's producing a signal far enough off that the ECU can't make any kind of guess how to keep it running.

Those include the O2 sensors, the IAT sensor, the ECT, and I'm sure others that the real tuners in here will chime in with.

Also, I forgot at first - be sure to check what they're MONITORING ... they may be producing a perfectly accurate signal that's so far off what the ECU can handle, after all! Also, does it not stay running if you keep the throttle open? Maybe poll for codes anyway (there are several that won't light the CEL due to not being emissions bad per se.)

RwP
 
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I'd first look at the sensors that come on line when the ECU goes closed loop; sounds like one's producing a signal far enough off that the ECU can't make any kind of guess how to keep it running.

Those include the O2 sensors, the IAT sensor, the ECT, and I'm sure others that the real tuners in here will chime in with.

Also, I forgot at first - be sure to check what they're MONITORING ... they may be producing a perfectly accurate signal that's so far off what the ECU can handle, after all! Also, does it not stay running if you keep the throttle open? Maybe poll for codes anyway (there are several that won't light the CEL due to not being emissions bad per se.)

RwP


Thanks for the quick reply.

Wouldn't a bad sensor or 'out of range' reading have been caught during the KOER test? I'm using a pro OTC scanner with the Pathfinder cartridge (guided troubleshooting) that the previous owner was nice enough to include with the car. I'm not relying on the CEL (which is not lit by the way).

The car will not stay running after a few minutes (it varies from 1-10 minutes) no matter what's happening....idling, throttle up, in gear, out of gear, and usually it will die long before the temp comes up.
 
Can ANYONE tell me if my 92 will run with an 89 computer (both auto)? It doesn't have to run perfect, I just need to see if it will STAY running on another ECU that I have sitting here.

K
 
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