Slight misfire at idle

[danhex0]

spun a bearing 2023, engine was built in 2024 with new coils plugs and injectors and ran perfect for around 6-7k miles. Recently started getting p0300 p0301 p0302 and p0303 codes and I can feel a shake at cold start. When it warms up it’s not as noticeable but I can feel it in the seat and the rpms wiggle around 4-500 rpm however when I drive it’s completely normal and I have zero power loss. I disconnected my dinan ecu and went back to stock but nothing changed.

Any knowledge what to check next?

[eflo82]

Looks like you have a bank 1 issue, what are you using for diagnostics? You really need to get ista if you don’t already have it.

You can try swapping map sensors then O2 sensors to see if the faults switch to the other bank.

[danhex0]

I’m using the Carly and a foxwell scanner both showed the same codes, I’ve swapped the maf sensors before and nothing changed. There’s no codes for maf and they are completely dry and clean, ill try swapping the o2 sensors. Do I swap downstream, upstream or both?

[eflo82]

Originally Posted by danhex0

I’m using the Carly and a foxwell scanner both showed the same codes, I’ve swapped the maf sensors before and nothing changed. There’s no codes for maf and they are completely dry and clean, ill try swapping the o2 sensors. Do I swap downstream, upstream or both?

Only the upstream O2 sensors. The downstream are for cat monitoring.

[eflo82]

Could also be a throttle body issue but those are much harder to access/ diagnose. I would try spraying starting fluid around intake components while the car is idling to look for a vacuum leak. Check out some YouTube videos on how to find a vacuum leak.

[danhex0]

Originally Posted by eflo82

Could also be a throttle body issue but those are much harder to access/ diagnose. I would try spraying starting around intake components while the car is idling to look for a vacuum leak. Check out some YouTube videos on how to find a vacuum leak.

I found a crack in the intake hose between the maf and turbo in guessing that’s definitely the problem

[eflo82]

Nice find! Agree, that’s more than likely your problem.

[danhex0]

Originally Posted by eflo82

Nice find! Agree, that’s more than likely your problem.

I replaced that cracked intake peice and there’s no more check engine light or code for any engine misfires but the rpms still wiggle slightly and I can feel inconsistent vibrations in the seat like it’s still misfiring. I have one code for the coolant outlet temp sensor but I don’t see how that would cause this problem. Only thing I can think of since th code isn’t coming back is to drive it around and have it reset ecu adaptations.

[danhex0]

Originally Posted by danhex0

I replaced that cracked intake peice and there’s no more check engine light or code for any engine misfires but the rpms still wiggle slightly and I can feel inconsistent vibrations in the seat like it’s still misfiring. I have one code for the coolant outlet temp sensor but I don’t see how that would cause this problem. Only thing I can think of since th code isn’t coming back is to drive it around and have it reset ecu adaptations.

Update: it’s misfiring again same bank one issue

[danhex0]

Originally Posted by danhex0

Update: it’s misfiring again same bank one issue

Update again: I swapped a coil from bank 2 over to 1, no change, checked spark plugs and they look normal, o2 sensors, normal, all plugs coils and injectors replaced ~7k miles ago, only thing I can think is there’s a small vacuum leak somewhere on bank one. What’s the best way to smoke test?

[Maxixt]

Check ,maby hpfp is loosing pressure when engine off, normaly when you turn off engine , in first 15 sec pressure in rail will rise than hold for rather ling time , if you turn off engine and rail pressure drops every second , replace hpfp.