1999 GMC Jimmy Do I have a blown motor

Tiny
PARMAN440
  • MEMBER
  • 1999 GMC JIMMY
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 135,000 MILES
I was on my way to work and my Jimmy all of a sudden lost power.
It idles rough. I had a guy tell me that I may burned a hole in a piston.
I used my QBII code reader and got a p0300
Which is a random misfire on all cylinders.
I guess what my question really is.
If I had a hole in the piston of one of the cylinders
wouldn't that cylinder be the one that comes up with a problem.
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have the same problem?
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Wednesday, January 6th, 2010 AT 5:15 PM

5 Replies

Tiny
MERLIN2021
  • EXPERT
More common problem would be the fuel pump, you didnt just gas up did you? Test fuel pump pressure. you need 60+ psi...

http://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Compression test would reveal the hole in piston thereoy, and so would a lot of gas in the oil!
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Wednesday, January 6th, 2010 AT 5:31 PM
Tiny
PARMAN440
  • MEMBER
I just had the fuel pump replaced last winter.
Yes I did just fuel up but tank is not full.
I wondered if I may have jumped timing
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Wednesday, January 6th, 2010 AT 5:36 PM
Tiny
MERLIN2021
  • EXPERT
If it sounds like a deisel engine you may have jumped time, but a compression test will show weak cylinder(s). Is the service engine light on? If yes, Autozone reads them for free, post all codes found here. I asked about the gas because GM pumps anre cooled by the fuel in the tank, and if you drive around with 1/4 and less a lot then fuel it, and run into performance problems after fueling, the pump is the usual suspect, just because you cahnged it last year dosent mean it's not on the way out now!
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Thursday, January 7th, 2010 AT 1:26 PM
Tiny
PARMAN440
  • MEMBER
Thas is what I have been thinking it is, the timing thing. Just by the way it runs. I am planning on doing a compression test this weekend, just to rule out what another guy said it could be. He said I had burned a hole in a piston.
The only code I got from the QBDII tester was a P0300. A random misfire on all cylinders.
Once I do the compression test, is there a simple way to check the timing. I was told I could take the distributor cap off and rotate the cam counter clockwise then back and watch the rotor while I am doing to see if it moves freely or there is hesitation.
Does that sound right?
And yes I agree that just because I replaced the fuel pump module last year, it does not mean it could not gone bad again.
I try not to ever let the tank go below a quarter.
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Thursday, January 7th, 2010 AT 6:04 PM
Tiny
MERLIN2021
  • EXPERT
Put #1 piston at TDC, then look at the timing mark on the crank pulley, it should be at the pointer.
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Friday, January 8th, 2010 AT 2:46 PM

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