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ZZDaryl, Chevy Technician
Category: Chevy
Satisfied Customers: 12547
Experience:  28 year experience, Master Mechanic
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2002 chevy: eng light only comes on at 1800..2000rpm

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2002 chevy 2500hd 4x4 auto, 6.0 eng... I have a p300 code multi cly misfire. ck eng light only comes on at 1800-2000rpm and above. I can't feel the miss. I did tune up, sprayed around intake with starter fuild no rpm change, engine doesn't idle or run rough. tested fuel rail reg and not leaking. even with fuel reg plugged off pressure around 60psi still ck light comes on. buddies snapon scanner says 4 clys misfiring the most and not in firing order or next to each other. only 69k on truck. the only thing I know to do next is to move a couple injectors around to see if same injector misfires... I blogged it and there a lots of p300 codes on this engine and some guys have changed everything including intake,fuel pump, sensors, and still has same probelm. I thought if gm mechanic out there they may have seen this before. Only getting about 7mpg but has 411 rearend.
A crankshaft relearn procedure will usually fix this problem, I am not sure if the scan tool you have can do that if not a Tech II scan tool will be needed.
Customer: replied 5 years ago.

If i had to take to dealer which here is 110 bucks an hour how long does this take to do ? also what causes this to happen ? does it do any good if I disconnect battery would that make system relearn itself.. have you seen this before ? I know if I take to dealer and isn't the problem i'm at their mercy with high labor rate . thanks, guy

I have seen this a 100 times at least, it does not always fix the problem but most of the time it does especially with the given symptoms. It only takes about 10 minutes, for the process, I would check you local repair shops many of them have the Tech II and will do it much cheaper than a dealer. Disconnection the battery will do not good it actually is the cause of the problem.
Customer: replied 5 years ago.
ok I've had this truck since light started coming on and never disconnected battery yet... what would be my next step to tell them to do if this doesn't fix it ?
The fuel injector are also common to get dirty and cause a little misfire so if all other bases (plugs, wires, ect) have been changed I would get a professional injection cleaning done.

Below is a pic from a data base of common problems maybe it looks familiar,



Customer: replied 5 years ago.
thanks, XXXXX XXXXX diesel engines using a scanner can do injector pop off test or even cly kill test and listening to engine you can hear the difference but this engine isn't running rough enough to kill clyers. can tech2 scanner check each injector pressure or pop off ? just trying to get as much info as I can because when I take it somewhere if they don't know what to do next I have some answers. guy
Customer: replied 5 years ago.

when i take it to shop if they do relearn doesn't fix then injection cleaning doesn't fix what is my third to tell them ? will a computer modual do this in case they say I need one and I know how much they cost ?

Yes they can do a injector test with the Tech II scan tool. I would do a compression test if the other tests show nothing I would also do a fuel sample to be sure the fuel is not contaminated.

Customer: replied 5 years ago.
ok thanks, I've run a couple of tanks of fuel so not fuel...I can do compression test no smoke out tail pipe so a dry test be good enough ?
I would do a complete compression test on all cylinders, running, not running, wet, and dry. There should not be much difference from one cylinder to another.
ZZDaryl, Chevy Technician
Category: Chevy
Satisfied Customers: 12547
Experience: 28 year experience, Master Mechanic
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