jamesdking
Newbie
This sounds a lot like the threads I’ve been reading but I’m lost and defeated…
98 Yukon 5.7 vortec 200,000 miles
p0300 and rough misfire under load or on hills at highway speed. Won’t accelerate past 2000rpm when it starts happening. Makes living in the mountains tough
parts replaced in order:
Plugs
Wires
Fuel filter (had black gas in it)
ICM
Rotor and Cap ( timing light was erratic when placed on any wire)
Distributor
Rotor and cap again
Replaced cat
Spider MPFI (modern)
Intake gasket (upper)
Wires and plugs checked again
Sprayed down with brake clean looking for vac leak
Cap and Rotor again!
Fuel Pump (cut a hole in floor) tank looked plastic and clean through the opening anyway.
runs better than it ever has. Until you get to a hill. Still throws a code p0300 or sometimes a specific cylinder 0305 and 0304 but always accompanied by 0300.
fuel pressure at idle 51
Fuel pressure at koeo 55
Seems low and didn’t change with new pump even a little bit.
Thoughts:
Fuel filter plugged again from **** in the lines
Multiple bad replacement parts
Timing is set to damn near 0 CPM
Haven’t touched cam or crank sensor
Haven’t cleaned MAF yet
Is it time to compression test for stuck valves or floating?
All 8 plugs looked like this after 6 months of this problem.
98 Yukon 5.7 vortec 200,000 miles
p0300 and rough misfire under load or on hills at highway speed. Won’t accelerate past 2000rpm when it starts happening. Makes living in the mountains tough
parts replaced in order:
Plugs
Wires
Fuel filter (had black gas in it)
ICM
Rotor and Cap ( timing light was erratic when placed on any wire)
Distributor
Rotor and cap again
Replaced cat
Spider MPFI (modern)
Intake gasket (upper)
Wires and plugs checked again
Sprayed down with brake clean looking for vac leak
Cap and Rotor again!
Fuel Pump (cut a hole in floor) tank looked plastic and clean through the opening anyway.
runs better than it ever has. Until you get to a hill. Still throws a code p0300 or sometimes a specific cylinder 0305 and 0304 but always accompanied by 0300.
fuel pressure at idle 51
Fuel pressure at koeo 55
Seems low and didn’t change with new pump even a little bit.
Thoughts:
Fuel filter plugged again from **** in the lines
Multiple bad replacement parts
Timing is set to damn near 0 CPM
Haven’t touched cam or crank sensor
Haven’t cleaned MAF yet
Is it time to compression test for stuck valves or floating?
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All 8 plugs looked like this after 6 months of this problem.
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