1993 GMC Sierra 4.3L drivability problem

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wrench - 02 Jan 2006 02:20 GMT

Recently it began backfiring thru the TBI under load (going up a grade).
Sometimes it's severe, sometimes it pops just once. Cap and rotor were changed
but no no change in the symptom. Drives fine while cruising, idles fine, no SES
light or codes.

Any pointers out there?

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benick - 17 Jan 2006 02:13 GMT

> Recently it began backfiring thru the TBI under load (going up a grade).
> Sometimes it's severe, sometimes it pops just once. Cap and rotor were
[quoted text clipped - 11 lines]
>haven't had the 600 plus to do it yet.Still haven't recovered from
>Christmas yet...LOL Good luck.

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pkurtz2 - 24 Jan 2006 04:47 GMT

>> Recently it began backfiring thru the TBI under load (going up a grade).
>> Sometimes it's severe, sometimes it pops just once. Cap and rotor were
[quoted text clipped - 11 lines]
>>haven't had the 600 plus to do it yet.Still haven't recovered from
>>Christmas yet...LOL Good luck.

This sounds like a timing issue. When you go up a grade, or have a loss of
power, it sounds like your timing isnt retarding enough. I cant remember
though whether you have vacuum advance on those vehicles anymore or not.. If
you have it, check for a vacuum leak. If you dont have it, the check your
crankshaft sensor.

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