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Misfire/rough running at cruising/idle, runs fine under boost
Posted: Mar 26, 2023 5:06 PM
by Nnobile
Hey all, trying to isolate a recent issue on my e28 m30 turbo set up. Overall car has ran great for months on my current tune and set up until driving home yesterday noticed an intermitent misfire/rough only at light throttle/highway cruising. Seems to be off at Idle as well. Underboost and any load car is pulling great with no issues/hiccups. Afr's where they should be. I was driving hard yesterday, issue showed up maybe 15-20 minutes after spirited driving. Noticed this morning car seems to be a bit more rich than it should be during cold start and then started running rough as it warmed up. Once again under boost had no issues but only under very light load. Would appreciate any input or if anyone see's anything on my datalog that i am not. only thing i noticed is my battery voltage seems a bit wonky on my data log. planning to pull plugs this week to see if I have a possible stuck open injector? Thanks greatly- Nick
Also not seeing how to upload my datalog on here?
Re: Misfire/rough running at cruising/idle, runs fine under boost
Posted: Mar 28, 2023 2:04 PM
by M. Holtmeier
You can email me your .msq and .mlg files and I'll take a look.
hturbo.service@gmail.com. Plugs are always the first thing when something seems off. Sounds like maybe a vacuum leak, or a fuel system issue. Hard to tell with stand alone. You are sure idle and cruise AFRs are the same?
Re: Misfire/rough running at cruising/idle, runs fine under boost
Posted: Mar 29, 2023 8:55 AM
by Nnobile
M. Holtmeier wrote: Mar 28, 2023 2:04 PM
You can email me your .msq and .mlg files and I'll take a look.
hturbo.service@gmail.com. Plugs are always the first thing when something seems off. Sounds like maybe a vacuum leak, or a fuel system issue. Hard to tell with stand alone. You are sure idle and cruise AFRs are the same?
Hey thanks for the reply! Will get a a copy of everything over to you tonight. Was planning to pull plugs this weekend and see what they look like. Seemed to be more rich when just at idle (11s) leading me to think potential stuck open injector and maybe its not affecting the car underboost. Also was talking to the angry ass solutions guys this past weekend at a car show, they mentioned about the collab with you for the expansion tank strut brace! Will definitely be picking one up when they become available, has been my biggest hold back from doing flipped throttle body setup!
Re: Misfire/rough running at cruising/idle, runs fine under boost
Posted: Mar 03, 2024 11:43 PM
by solarinterfere
Nnobile wrote: Mar 26, 2023 5:06 PM
Hey all, trying to isolate a recent issue on my e28 m30 turbo set up. Overall car has ran great for months on my current tune and set up until driving home yesterday noticed an intermitent misfire/rough only at light throttle/highway cruising. Seems to be off at Idle as well. Underboost and any load car is pulling great with no issues/hiccups. Afr's where they should be. I was driving hard yesterday, issue showed up maybe 15-20 minutes after spirited driving. Noticed this morning car seems to be a bit more rich than it should be during cold start and then started running rough as it warmed up. Once again under boost had no issues but only under very light load. Would appreciate any input or if anyone see's anything on my datalog that i am not. only thing i noticed is my battery voltage seems a bit wonky on my data log. planning to pull plugs this week to see if I have a possible stuck open injector? Thanks greatly- Nick
dinosaur game
Also not seeing how to upload my datalog on here?
Check for Diagnostic Trouble Codes (DTCs) using an OBD2 scan tool and note any misfire/lean/rich related codes.
Re: Misfire/rough running at cruising/idle, runs fine under boost
Posted: Mar 04, 2024 12:19 AM
by M. Holtmeier
solarinterfere wrote: Mar 03, 2024 11:43 PM
Check for Diagnostic Trouble Codes (DTCs) using an OBD2 scan tool and note any misfire/lean/rich related codes.
Exactly how would you go about doing that?
Re: Misfire/rough running at cruising/idle, runs fine under boost
Posted: Mar 04, 2024 9:12 AM
by tschultz
Are your plugs too cold for the colder weather and fouling out a bit? Just another thought if the injectors all turn out to be working properly...
Re: Misfire/rough running at cruising/idle, runs fine under boost
Posted: Mar 06, 2024 9:27 AM
by turbodan
If you have an injector stuck open it should run pretty poorly. Whichever cylinder is affected would be flooding with fuel and constantly misfiring. Never seen that though. They sometimes leak a little after shutdown or simply don't work at all. The most common failure mode for injectors in my experience has been external leakage.
I would be this misfiring is AFR related. I didn't see any mention of cruising AFR.