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1998 GMC Sierra 1/2 ton 4.3L


reyes45's Avatar
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05-07-03, 05:47 PM   #1  
1998 GMC Sierra 1/2 ton 4.3L

My truck started running rough whith check engine light on.
I scanned it with my OBDII scanner and got code P300(multiple
cylinder misfire) so I changed spark plugs, dist. cap, rotor, and
wires and it did not fix the problem. #3 plug dark with gas odor.
What else could it be? Thank you.

 
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05-08-03, 03:58 AM   #2  
Joe_F
Could have a bad coil, or commonly on the 4.3 the fuel injector poppets get clogged and it will run rough. Could also have a bad fuel pressure regulator diaphragm.

How's the fuel pressure?

 
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05-08-03, 03:27 PM   #3  
1998 GMC Sierra 1/2 ton 4.3L cylinder misfire

Fuel pressure is good. problem comes from misfire. I suspected
sparkjump in dist cap but that wasn`t the case. hink I`ll have
the ign. module and coil checked. What do you think?
Thank you for your reply!

 
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05-08-03, 03:43 PM   #4  
darrell McCoy
Joe's gotcha covered on the partial clogged fuel injector. If so GM has a decent additive. Not recommended for continous use however. Part number escapes me right now but is about 18 bucks for a bottle.

 
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05-08-03, 04:01 PM   #5  
Joe_F
Original poster: How do you know the fuel pressure's good? How was it checked?

 
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