Trying to figure out this misfire/stumble
09-16-2018, 07:33 PM
#1
Launching!
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Trying to figure out this misfire/stumble Figure I'd post here for a little insight. 02 Z28 cam and full bolt ons 6 speed. Car started stumbling real bad. Like to the point where it's pretty much not drivable. Like I press the pedal to the floor and nothing. A bunch of popping and missing. If I baby the gas it will still misfire a little but I can at least drive a bit. Only code is P0151 for passenger front o2. Replaced plugs and wires, replaced the o2 sensor's replaced the fuel filter. Checked and wrapped up the wiring from the PCM to the passenger o2, and the crank sensor. And nothing only thing left would be the coils and injectors on that side and to replace the actual crank sensor but I haven't gotten any misfire codes. Pulled the plugs after a couple days and they were black. I should also add that it takes a while to crank the car over. Like 5 to 10 seconds of cranking. Any insight?
09-16-2018, 08:42 PM
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ModSquad
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I’d throw a fuel pressure gauge on it to check, as well.
09-17-2018, 12:12 PM
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Long Crank could be a leaking injector, this would cause a misfire and long crank times, the O2 reads the misfire as a lean condition, fattens up the fuel curve on that side and then you have a crappy running engine and black plugs. First make sure the O2 is reading correctly and replace both banks at the same time with GM O2 sensors, no aftermarket crap, Then check injectors, install a fuel pressure gauge and see if fuel drops off to zero when you shut it off, let it sit for awhile, crank it while you watch gauge, see how long fuel pressure takes to get to specs.
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09-18-2018, 11:41 AM
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I came across a ground that I believe to be in the wrong spot. There is a braided ground strap that goes from the passenger front coil mounting bracket bolt to the body. Every other LS1 I've looked at has no ground strap there. It goes from the coil bracket bolt by the alternator then goes to the body of the car. I believe this strap is supposed to go from the block to the body on the passenger side. I chased this strap and noticed it was torn and hanging by a thread in a spot. Is this strap in the wrong spot? Would the fact that its hanging by a thread and in the wrong spot cause me serious issues?
