1999 GMC Sierra, Running problem

PCHEFSONYA

MEMBER
1999 GMC SIERRA
178,000 MILES

This is a 1999 K1500 4.8 liter. This truck was towed in after sitting for over a year. The Fuel Pump was bad, so installed new pump and truck would run but it ran rough. Found corroded wires on Cylinder 1 and 3, installed new wires and plugs, ran better but still running rough. I hooked it to Snap-On scanner and got a Code PO300, misfire. Checked data screen on scanner and got a Cylinder 5 and Cylinder 7 misfire. Performed compression test and cylinders checked Okay. Performed spark test and had spark to 5 and 7 cylinder. I also performed a fuel injection cleaning and it didn’t change 5 and 7 misfire. Any ideas what I should try next?

Monday, January 2nd, 2012 AT 11:32 PM

3 Replies

RIVERMIKERAT

MECHANIC
6,110 POSTS

ENGINE ADJUSTMENTS -1999 GMC Sierra 1500
Page 1 of 1
Adjusting Camshaft Retard Offset

1.
Turn ignition off. Slightly loosen distributor hold-down bolt. Start engine. Increase engine speed to more than 1000 RPM.
Using scan tool, monitor Cam Retard Offset. To adjust for a negative reading, rotate distributor counterclockwise. To adjust for a positive reading, rotate distributor clockwise.
Continue to adjust as necessary until zero degrees plus or minus 2 degrees is attained. Turn ignition off. Tighten distributor hold-down bolt to 25 ft. Lbs. (34 N.M). Start engine. Increase
engine speed to more than 1000 RPM. Using scan tool, verify camshaft retard offset adjustment.

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Monday, January 2nd, 2012 AT 11:40 PM

PCHEFSONYA

MEMBER
31 POSTS

This truck is Distributor less. It has individual coil packs for each cylinder. I tried switching pack 3 and 5 but it didn't change the miss in the engine. Any ideas?

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Tuesday, January 3rd, 2012 AT 3:13 PM

RIVERMIKERAT