Re: Service engine light??


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Posted by towbeast (130.36.62.224) on 13:33:26 02/22/13

In Reply to: Re: Service engine light?? posted by OnBelay

I had a random misfire on my 99 K3500 pick-up. My son set me up with a laptop, $100 professional program and a cord to connect to the car. It shows the misfires occurring. Turns out cylinder #8 was the only one misfiring. Why it throws the random misfire code when one cylinder was the only one having a problem is beyond me. But a new wire and plug fixed it. The wires and plugs had less than 15K miles on them.
Have used that laptop/wire/program to diagnose several problems on our cars: TPS, speed sensor, vacuum leak to name a few. Comes in real handy.

Towbeast



: : '99 GMC Sub,K2500,454,3/4 ton, 4wd,auto trans, ac, nearly 200K on the girl.
: :
: : SES light comes on occasionally. Stays on for a few days then goes off. A buddy put a scan tool on it and got a "random misfire" code.
: :
: : It happens when its cold for here. Say 20 or below (I know that's not cold).
: :
: : Any thoughts or experience on what might cause it to throw the code?
: :
: : Thanks
: : Guy
:
: Sorry to give you the smarta$$ answer, but....
:
: I'm pretty sure you have a random misfire.
:
: Check, in this order:
:
: plugs
:
: wires
:
: coil
:
: My best guess would be a plug that is slightly fouled or has a crack.
:
: You don't really give enough specific. "Occasional" to some might be every six months, and to to others might be every 6th time you start the engine.
:
: A true scan tool (not just a code reader) will give you access to a misfire counter, so that you can check the history and hopefully find which cylinder.
:
: So, it becomes a question of "how bad do you want it to stop?"




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