Misfire on cylinder 1

[MrScrublord]

Hey guys, I’ve had a misfire on cylinder 1 and only that cylinder for some months now. I physically can’t tell when it misfires, only rarely when I’m idling and it does the rpm’s will fluctuate oddly and I’ll feel it. It’s very random too, could happen once a day or ten times a day. The CEL is constantly on, the traction control light will come on and the CEL will flash sometimes with it. So far I’ve ruled out the spark plugs, coil packs, fuel injectors and the tune. I’m running a stage 2 tune from the Open Flash tuner which is slightly modified to bump the idle rpm’s up slightly. I’m worried it may be something to do with the wiring for some part of the ignition process. I’ve had a lot of issues with the wiring in the engine harness in the past which is now fixed, had to creat a few jumpers to fix some fried wires, but none of which had anything to do with cylinder 1. I’m completely stumped right now and don’t even know how I’d go about testing any of the wiring for the fuel injectors or coil packs since if something is fried, it would be a more consistent misfire? I don’t have much control over recreating the misfire either because it appears to be completely random.

[humfrz]

What code does your car show?

Erase the CEL and see if it comes back.

Switch the #1 coil pack.

[blsfrs]

What happened that you had to fix "fried wires"?

[MrScrublord]

Originally Posted by blsfrs

What happened that you had to fix "fried wires"?

I put in a couple hefty subwoofers that required me to replace the stock battery connectors with larger ones that can hold more wiring. I removed the negative terminal which(unbeknownst to me at the time) contains the battery current sensor and decided to ground the small wires going into it. It ended up killing my ECU, throttle body and fried wiring going to the throttle body, MAF and Accelerator pedal. Had a dealership replace the ECU and flash it for me and I decided to fix it the rest of the way since they were trying to scam me out of a lot more money. After fixing that mess I had a good period of time with no problems which makes me think this isn’t directly related to that incident?

[MrScrublord]

Originally Posted by humfrz

What code does your car show?

Erase the CEL and see if it comes back.

Switch the #1 coil pack.

Currently the codes on my car P0301 for the misfire and only a couple days ago I had C1201 pop up for the ABS system, I don’t have an ABS dash light on though. I’ve cleared the codes many times before and P0301 always comes back and has always been a permanent code since this problem began. After working on the spark plugs, the permanent code is gone, which makes me feel like I fixed something.
The last thing I did was check the spark plugs, the one in cylinder one was a different model than the other 3 and was gapped way too small. I fixed the gap and then swapped it around to cylinder 2 to see if it was the spark plug, so far no. I plan on replacing the spark plugs soon anyways.
I have P0134(front O2 sensor no activity) disabled from popping up, couldn’t fix it and read on a bunch of forums that it’s common if you have catless headers and it’s ok to disable.
P0140(rear O2 sensor no activity) popped up last week when I swapped tunes to see if my tune was causing it. I’ve found that to be common whenever I change tunes and it disappears in a day or two.

[Ignore Your Doctor]

sounds like either coil pack going bad or DI ecu. if you have a friend with a brz swap the DI ecu and see if you have the same CEL

[humfrz]

Originally Posted by MrScrublord

Currently the codes on my car P0301 for the misfire and only a couple days ago I had C1201 pop up for the ABS system, I don’t have an ABS dash light on though. I’ve cleared the codes many times before and P0301 always comes back and has always been a permanent code since this problem began. After working on the spark plugs, the permanent code is gone, which makes me feel like I fixed something.
The last thing I did was check the spark plugs, the one in cylinder one was a different model than the other 3 and was gapped way too small. I fixed the gap and then swapped it around to cylinder 2 to see if it was the spark plug, so far no. I plan on replacing the spark plugs soon anyways.
I have P0134(front O2 sensor no activity) disabled from popping up, couldn’t fix it and read on a bunch of forums that it’s common if you have catless headers and it’s ok to disable.
P0140(rear O2 sensor no activity) popped up last week when I swapped tunes to see if my tune was causing it. I’ve found that to be common whenever I change tunes and it disappears in a day or two.

There ya go fer starters -

[blsfrs]

Have you checked for a vacuum leak?