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Misfire

Teddyb

Teddyb

New member
Ok I have a 2000 Buick Regal GS and she developed a bad misfire on cylinder 3. Im in school so the first thing I did was check the plugs. The plugs were ok I adjusted the gaps and reinstalled them. I still have the skip on cylinder 3 history shows its been misfiring 52k times and counting. So I checked the coils and icm. They all checked out to be good. So I check the injectors and there find I put a noid light on the electrical connector and they all check out. So now its getting frustrating I have 2k miles on this engine stock engine had piece of the piston missing on cylinder 4 mainly and a few others but not as bad as cylinder 4. So I recently did a compression test on her and the lowest reading was 172 p.s.i. to the highest 185 p.s.i. and all between these numbers seemed to be excellent. We got the engine from a 98 Buick Riveara supercharged. New head gaskets, head bolts intake the whole nine yards. And after all that its still misfiring. Oh I just put a set of wires on her to no avail. If you all have an other suggestion please and I mean please feel free to respond im all ears you all helped me with my transmission so I have the upmost respect and confidence in you all thanx in advance.
 


try swapping plug wires yet? and try switching the injector as well, and switch the spark plug as well see if the misfire moves with the swapping around of the parts.

the plug could have a hairline crack in the porcelain also. sometimes hard to see.
 
I'm seeing more and more misfire threads... Wish I could offer some help but it seems you tried everything I would have suggested. Please let us know when/if you find the problem.
 
the noid light only lets you know if the PCM is sending signal to the injector. do a power balance test by unplugging and plugging back in your injectors. note the rpm drop

if no rpm drop you have found your problem injector. repeat same process with plug wires, or attach a spark tester
 


if you had really swap plugs around wouldn't you have seen that the first time around?

the next maybe bad part is, i've yet to see a gap close by its self, you may have a chipped piston, and it tagged the plug on its way out the valve.
 
Are you running 91+ octane in that thing? Seems odd that you blew up #4 on the old motor, and now most likely chipped #3 on this one. Something's not right here. Stock pulley size on the SC?
 
Ok im goin to school for automotive and my trusted classmate and I were in a rush to put the plugs badck in so I can go home and he told me today that he may have put the plug In while it was closed because he told me he dropped the plug. So he bought me a set of platinum ac delcos to put in it. Number 3 cylinder had a memory misfire of 32k but after the plugs I installed the snap on ethos and its reading no misefire on 1, 2, 3, 5, 6 but 4 has a very slight misfire maybe 8 to 10 misses in a 30 second period. So I hope I can iron this thing out cuz the chipped piston is scary to me.
 


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