Hey all, looking for some advice from the wise.

2006 Mini S, have a random stumble which originally i took as a misfire. However after monitoring things via INPA it seems to be having fuel adapting issues. When the stumble happens the fuel trim either jumps way up, or way down (at idle speed). Further INPA is constantly going from active to inactive on the Rich Fuel Mix light (at idle).

Has anyone seen this issue, steps to correct it or advice? Obviously 02s are the main culprit at this point, and fuel pump/filter planned on being changed before these shenanigans. Also understanding it could be a vacuum leak or map sensor issue, but before throwing parts at it!

No engine codes, no faults on ISTA

Thanks for any advice

 

Run a bottle of injector cleaner in the next couple of fill ups to see if that makes a difference. A clogged injector may be causing problems. Also, a vacuum leak would cause a lean mixture, not a rich mixture. Check your SC boots. They often twist/fold on the underside during install and allow an air leak. Otherwise, go old school and create a thick mix of dish soap and water and pour it on the areas that may have an air leak to ID the problem. If these don't work don't discount an O2 sensor problem. You have two (upstream and downstream) O2 sensors that modulate fuel/air delivery.

 

hard to say without codes...

I'd think the O2 sensors are a good place to start. other sensors are involved here. tmap and map is what im thinking

 

Thanks Lads, yes codes would be nice wouldn't it!

I have been searching for vacuum leaks as they would account for the leaning out as you say. Unable to locate any yet, I'll have to toss into service mode and check the charge pipe area.

I like the injector cleaning idea, definitely could play a role. Unfortunately wasn't able to remove my injectors off the intake due to being a rust belt car. Thankfully have a spare intake so I may work at getting those out and swap things around.

 

Update, found the culprit. Supercharger charge pipe gasket.

After attempt and attempt to find a solution for this issue, smoke tests you name it. I said screw it and lets drive it until it gets worse, that did not take long! Maybe did about 100km since posting about this, took the car out for a "sunday" cruise and it started misfiring about half a block from home. I was excited, because everything ignition related was brand new and it could only mean the issue was more prevalent. Read the misfire code and it was P0302 which is an odd cylinder to misfire on these engines unless you have catastrophic internal engine issues (which i had just rebuilt). Also happily had p1498 i was waiting for....

Brought the car home, inspected everything vacuum related, nothing stood out. Went half way into service mode (enough to move the rad forward and inspect the charge pipe while the car was running.) Sure enough the gasket supercharger side was gone and visually noticeable with smoke tests.

Hope this info may be helpful to someone, as forums without an answer are poop.
Cheers all

 

Good to hear you found it!

 

Yes, that green gasket is a PITA to install properly -- really dumb BMW design. It helps to remove the throttle body before attempting to install the charge tube - promotes a better seal.