[Spoolin1]

Hey guys,

Hopefully someone can help me out here. I've been having cylinder 6 misfires on Cobb 1+ tune for a long time and it keeps getting worse. Can't even give it too much throttle now while driving or it'll misfire bad. What I did to try and fix things are... replaced all coils, replaced all injectors, replaced all spark plugs with the ZGR6STE2 Bosch's and have now just done the walnut blast and it's still misfiring in cylinder 6 and now I'm getting fuel pump plausibility. What's the deal here? I can't figure out this issue and the BMW master mechanic has no clue either at this point. He suspects the tune so I changed the Cobb tune to the factory like 0 tune and it's still doing it. The mechanic doesn't think it's the fuel pump since it's been changed within the last 20k miles and typically he states that a true fuel pump issue would have other cyclinders causing issues, not just cylinder 6. The car only has 43000 miles and is an 07. Could the Cobb have hurt one of the DME drivers?

Can anyone help?

[mike@x-ph.com]

i have seen DMEs going bad. Not Cobb related seen it on stock as well.
Also do a pressure test and see how cylinder 6 is doing.

[mojobmw_e90]

U try swapping the coils around and see if it follows?

[Spoolin1]

We haven't swapped coils since they are brand new and from BMW, same with injectors but now that I have removed the Cobb altogether, I'm getting cylinder 4 and 6 misfires. You can't even drive the car now and give it any gas in a high gear with a load on the engine or it'll start misfiring bad. Fuel pump plausibility keeps popping up now too so maybe it is the pump. Just weird its mostly cylinder 6 though. Its actually gotten worse now that I had the valves walnut blasted.

[///Mposter]

Did he code your injectors correctly? Did he use new seals or reuse old ones on the injectors?
If you look at your logs if you have ever done any, what are your pressures for HPFP and LPFP?

[Spoolin1]

Yeah, the injectors were coded correctly when they were put in by BMW. I haven't logged the fuel pressure yet but will. I know fuel pump plausibility is coming up occasionally but wouldn't that cause more than just cylinder 6 issues? I've only seen cylinder 4 come up once no with 6 being all the time. I can't even give it much gas driving now even on the stock tune. Is the HPFP the one that fails most often? It was changed before. Could there be an issue with the LPFP? Is it known to fail also?

[gabylonfive]

Check your low pressure fuel sensor. I had a similar issue and replaced that sensor to resolve it.

[///Mposter]

The thing is , if you have had a misfire badly in cylinder 6 and you didn't take it out and clean it then swap coils , then you have just left it fouled and with a different coil . The outcome would be the same. You must clean it off , make sure the coil is seated all the way down in its groove , then log on stock map. Look at HPFP and make sure that when the throttle is 100% , your HPFP value should not be less than 10. If it is then look at LPFP and if that value is in the 50's then you have a problem with LPFP supply. If the LPFP reading is 137 psi then your sensor is bad and is running max all the time.

[Spoolin1]

Originally Posted by ///Mposter

The thing is , if you have had a misfire badly in cylinder 6 and you didn't take it out and clean it then swap coils , then you have just left it fouled and with a different coil . The outcome would be the same. You must clean it off , make sure the coil is seated all the way down in its groove , then log on stock map. Look at HPFP and make sure that when the throttle is 100% , your HPFP value should not be less than 10. If it is then look at LPFP and if that value is in the 50's then you have a problem with LPFP supply. If the LPFP reading is 137 psi then your sensor is bad and is running max all the time.

Thanks. I'll check everything, clean cylinder 6 spark plug and check and swap coils. Then I'll do a log and post up what I find out. The fuel pressure sensor was replaced about a year ago so hopefully it's not that again.

[924er]

Originally Posted by Spoolin1

Thanks. I'll check everything, clean cylinder 6 spark plug and check and swap coils. Then I'll do a log and post up what I find out. The fuel pressure sensor was replaced about a year ago so hopefully it's not that again.

Yes it wouldn't hurt to swap. Sometimes new parts can be defective.

Now log your HPFP psi along with LPFP.
Cyl 6 is the last one to get fuel so it may be fuel related. I know this issue is going to have an obvious fix.

Honestly with e85 a LPFP psi of 50 is okay as long as the HPFP is holding up. I've been running in the 50s for a while now.

[msjt]

Make sure that the plate for the injectors isn't installed upside down. I had consistent misfires under anything more than light throttle until that was fixed.

[Spoolin1]

Originally Posted by msjt

Make sure that the plate for the injectors isn't installed upside down. I had consistent misfires under anything more than light throttle until that was fixed.

That's good to know man because what you describe is exactly what it's doing. Anything more than light throttle and it misfires. Although, on occasions, it would pull good and hard with no issues before the walnut blast and now it's just undriveable. I haven't had the time to do the checks and logs yet but will soon and report back.

[boostaholic786]

the cobb didnt have anything to do with it. you need to log just to see how your fueling looks but first, try and swap coils to see if it misfires on the cylinder you put cylinder 6 coilpack. also, make sure everything was put back together right after you got your walnut shell blasting done...since you all of a sudden had more issues after the blasting

[hotwired78]

i had similar issues. ///Mposter is correct. Need to clean everything off and reset the car's ECU to relearn. Sometimes new parts aren't always perfect, and that cylinder could've fouled your new components as well.

[Spoolin1]

Well, the issue ended up being a faulty new #6 injector and BMW ended up replacing it free of charge since I just had them all replaced less than 6 months ago. Let me tell you also that after the first walnut blast with only 43k only the clock, the stock tune feels much stronger. Can't wait to reflash the Cobb stage 1+ back in it now.

[FRMTL2_335i]

Miles on car? Stock clutch kit?

[Spoolin1]

43k and it's an auto.