c63amgpower

Gents, need some advice . I recently had redone my exhaust and software tuning . We tested it and ran with pump gas and everything was looking good. No issues . We had a drag event so I did as I usually do. Filled up with a race mix on the morning whilst going to the track . 10 km on running , my engine light flickers yellow and the car started misfiring and also idling high and then low. We plugged in the dashdaq diagnostics when I got to the track and it showed misfire on cylinder 8. We cleared the code and car was perfect for 1 run and thereafter the engine light back on and now misfire on cylinder 6,7 and 8. I ran the fuel out and filled up with normal pump gas and after a few km , the misfiring again. I don't know if it was the fuel since that was the only thing changed, however why didn't the problem now go away when I put normal pump gas. I ran race mixed fuel before and had no problem . Any ideas or suggestion .

mthis

What was the code.

c63amgpower

Sorry , Did not check code, was using a friends dashdaq. It said misfiring on cylinders .

Merc63

Lead in fuel??

Pull plugs.

Probably time for new plugs and primary o2 sensors.

Car runs closed loop 24/7. Your o2s are probably shot from the exhaust work and race fuel.

c63amgpower

Thanks , will check the plugs . Is there a way to confirm if your o2 sensors are shot and if it is the upstream or downstream sensor .

NS_C63

Upstream sensors. Downstream don't affect your setup.

Merc63

Yaypu get misfires lol. Plugs will be discoloured probably on affected side.

Critter

Well you have done 3 things, exhaust, software tune and then changed the fuel.
Pull the plugs probably original and should show signs lean, rich, gap not right, burnt tip.


Go back to the tune and look for the answer there.

c63amgpower

Thanks N_S , by any chance do you remember the code that came up on your Dashdaq.

abcut973

Probably P0300 range. That is the usual OBDII code for misfires.

NS_C63

Beginning operation: Read Codes (Read Codes)
Time: Sat Aug 23 08:16:23 2014
Reading Codes:

Mil Status is ON

1 DTCs

P0308: Cylinder 8 Misfire Detected

0 Pending DTCs

End of operation.
Time: Sat Aug 23 08:16:23 2014

NS_C63

And then again later for cylinders 6, 7 and 8

alpha26

Possible causes

- Faulty spark plug
- Clogged or faulty fuel injector
- Faulty ignition coil
- Fuel injector harness is open or shorted
- Fuel injector circuit poor electrical connection
- Ignition coil harness is open or shorted
- Ignition coil circuit poor electrical connection
- Insufficient cylinder compression
- Incorrect fuel pressure
- Intake air leak

http://engine-codes.com/p0308.html

jng204

I have the same issue of misfires on cylinders 6, 7 and 8. Car drove perfect to work and then started it up and instantly had the bad idle and drove bad.

I took it straight to the dealer and got service B performed at 77K miles and had them check on what is causing the bad idle/limp mode. The tech said compression is good, swapped coils and that did nothing.

He also unplugged the MAF sensor on the driver side (left) and I did as well and the car idles and drives like normal. I swapped MAF's and still get the misfire on 6, 7 and 8 so that rules out the MAF.

Should I try new spark plugs? Not sure if I need to change O2's since I did not get any faults regarding this and I have a Eurocharged tune ignoring the readings.

Thx

2010 E63 with the following MODs:
- ROW air box
- Eurocharged V5 tune
- MBH LT Headers with X-pipe and cat deletes

Jasonoff

A tune doesn't ignore your primary O2 sensors. They're a critical component and by the sounds of it the likely culprit.

jng204

Thanks. Spark plugs have been ordered since they are overdue anyway. Will post to see if this is one of the fixes.

Do you happen to know the primary 02 sensor part numbers for both sides? Made by bosch I assume.

jng204

Found the Primary O2 info. Bosch 17019

hachiroku

my front passenger side o2 sensor was causing me lots of misfires...I also was getting a o2 sensor error. after changing both, car felt great and picked up all lost power.

Mr. Lin

mine did the same thing.
just did plugs as well @ 73k
seems to be a common problem.