P0305 - please help with diagnostics (98 TransAm)
01-25-2015, 03:18 PM
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P0305 - please help with diagnostics (98 TransAm) P0305 - Cylinder #5 misfire detected
I have no history with this car. I just did a motor swap on it, bought the car with a popped motor. Bought a used motor with supposedly 70k miles on it.
I wish I could provide some history with it, but I can't.
swapped the motor out with the 99 Ls1, at first wouldn't start at all, for a few days, after diagnosing that, found it was bad gas, so now the motor runs.
took the car for a 1st drive, runs ok, but kind of chugs at idle, doesn't seem to be at a loss for power under acceleration or anything.
Driver side of motor knocks kind of loud, and with a steady, knock knock knock... beat, at idle... subsides almost completely after the motor warms. it's also very cold here in wisconsin, and i'm attributing this sound to the common LS1 cold start piston slap that I've heard a TON in lots of F-bodies and trucks with 5.3s
I have a tablet with the Torque Pro app, and although I've only put about a mile or two on the car since the swap, the car is showing a fault p0305, and a pending fault of P0141 (bank 1 o2 sensor position 2) - the voltage seems off in that sensor according to my Torque App
Strangely I've got no SES light on the dash... JUST FOUND OUT THE LIGHT DOESN'T COME ON EVEN ON INITIAL "KEY ON" POSITION. so I don't know what to do there either.
I pulled a spark plug WHICH ARE BRAND NEW BOSCH IRIDIUM 9602 - I had a complete set new, just lying around from a different LS1 project. Anyway, the plug for #5 looked just fine to me... so I don't know what to do there
I've done nothing yet, so please advise on how to diagnose, in what order, and what to look for. I do a lot of my own work so I'm not new in the garage.
my guess is:
swap a coil, reset computer, drive it and wait to see if the code moves to a different cylinder,
and do that also later, with the plug, and then the wire, and then the injector from cylinder #5 and see if I can get the code to move.
it not, then what? to I look to something in the valvetrain?
Thx in advance.
I have no history with this car. I just did a motor swap on it, bought the car with a popped motor. Bought a used motor with supposedly 70k miles on it.
I wish I could provide some history with it, but I can't.
swapped the motor out with the 99 Ls1, at first wouldn't start at all, for a few days, after diagnosing that, found it was bad gas, so now the motor runs.
took the car for a 1st drive, runs ok, but kind of chugs at idle, doesn't seem to be at a loss for power under acceleration or anything.
Driver side of motor knocks kind of loud, and with a steady, knock knock knock... beat, at idle... subsides almost completely after the motor warms. it's also very cold here in wisconsin, and i'm attributing this sound to the common LS1 cold start piston slap that I've heard a TON in lots of F-bodies and trucks with 5.3s
I have a tablet with the Torque Pro app, and although I've only put about a mile or two on the car since the swap, the car is showing a fault p0305, and a pending fault of P0141 (bank 1 o2 sensor position 2) - the voltage seems off in that sensor according to my Torque App
Strangely I've got no SES light on the dash... JUST FOUND OUT THE LIGHT DOESN'T COME ON EVEN ON INITIAL "KEY ON" POSITION. so I don't know what to do there either.
I pulled a spark plug WHICH ARE BRAND NEW BOSCH IRIDIUM 9602 - I had a complete set new, just lying around from a different LS1 project. Anyway, the plug for #5 looked just fine to me... so I don't know what to do there
I've done nothing yet, so please advise on how to diagnose, in what order, and what to look for. I do a lot of my own work so I'm not new in the garage.
my guess is:
swap a coil, reset computer, drive it and wait to see if the code moves to a different cylinder,
and do that also later, with the plug, and then the wire, and then the injector from cylinder #5 and see if I can get the code to move.
it not, then what? to I look to something in the valvetrain?
Thx in advance.
Last edited by dbusch22; 01-25-2015 at 03:31 PM.
01-25-2015, 07:18 PM
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If you have done a swap and think you have potentially broken a wire, you can always check for continuity on the PCM side to Injector 5.
If the engine has been sitting then it could be a stuck injector. You could try tapping the injector with a screw driver. I realize that sounds odd but you never know and it could free it...If that doesn't work you could always run power just to that injector and see if you can hear it clicking. According to WitchHunter Performance, they suggest using a 9V battery so you won't overheat the injector. I'm not a professional, this is just a suggestion.
If the engine has been sitting then it could be a stuck injector. You could try tapping the injector with a screw driver. I realize that sounds odd but you never know and it could free it...If that doesn't work you could always run power just to that injector and see if you can hear it clicking. According to WitchHunter Performance, they suggest using a 9V battery so you won't overheat the injector. I'm not a professional, this is just a suggestion.
01-29-2015, 07:41 PM
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So here's what i did.. went out, checked fuses, nothing there. Drained pressure off the rail after pulling the fuel pump fuse. Pulled #5 plug it, looked fine to me. Had someone crank the engine over, spark looked a little weak, pulled #7 plug out, spark looked the same, put #5 plug on #7 wire, still. ... same result.. so, put everything back together,the way it was. Fire it up, no miss. I've cleared out the computer, and am monitoring the system, i do not see any pending faults. I don't understand, but it seems to be"fixed" for now. Maybe just poor connection on the plug wires?