'89 GMC Sierra 4.3 Engine "Misfiring"

Nov 07, 2005 4 Replies
M

I posted a while back same issue. Sometimes it runs great and sometimes the engine "misses." Last time I noted that I had relatively new plugs, wires, cap, but had just changed thermostat to 150. This group recommended going back to 195, so I did, no change. Put new plugs in - no change. Strange thing is it isn't consistant. One day fine, next day terrible. When it's bad, if I keep the revs up it's not so bad (5sp manual). Could it be fuel filter? Coil? Faulty wires?



Thanks in advance,



MZ


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0

My dads 2001 S-10 got to running really bad like that. Come to find out the catalytic convertor was stopped up. Installed new one, runs like a champ. Just giving you another avenue to research.

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