Mysterious misfire
 

Hi guys,I have an 2005 x5 that has a bad misfire under any kind of load. For the longest time it wouldn't even throw a code. I replaced plugs and coils. Originally I replaced the coils with bremi ones. The problem continued. I finally took it to bmw they said its because I didn't have factory Bosch coils and wanted to sell me more new coils. I said no and took it back. I returned the bremi coils and replaced them with Bosch coils from our parts supplier other than bmw. I'm not sure if there is a difference in the Bosch coils from bmw and the Bosch from other parts places or not but the car still has the same issue. It finally came up with a multicylinder misfire cylinders 1 2 and 7. We have also replaced pcv valves. Not really sure where to go now I have read about problems with the eccentric shafts in those but don't wanna just start throwing parts at it. Anyone have any suggestions?

diagnosing problem is of paramount importance... to properly diagnose engine misfire, I would recommend connecting the car to diagnostic equipment or a computer running some software... you can do at a dealer at enormous cost, or indy for some savings, or yourself at a cost of a $40 for OBD cable and BMW-specific software and an WinXP laptop...

even if the engine does not throw codes, the GT1 or INPA can monitor live engine data and you can spot rough cylinders... it can also tell you what causing the misfire, but in most cases you would not be so lucky...

when using the coils i would suggest using either the OE coild from a dealer (too expensive) or OEM coils, in this case BOSCH... the BOSCH part must be identical to the BOSCH part of the OE coil - since you don't have a signature identifying your ride, i can only speculate that you have a V8, either 4.4 or 4.8... in this case, a BOSCH part # 0221504464 should be the one... for a plug, you can go with the BOSCH or NGK - both are OE suppliers... I went with NGK Iridium Ix Spark Plug (ZFR6FIX-11) from advanced auto parts, they are about $7 a pop, with a $25 coupon it cost me about $35...

since you have the cyls 1, 2 and 7 misfiring, have you tried to swap the coils and plugs around to see if the issue will follow?


Oh... and welcome to the forum... it seems that we got several newcomers onboard in last few days, and we did not have a chance to extend our welcome...

:)

Sorry. Yes it is a 4.4. As for the coils we have had three different sets in there and it runs the same with them all. We have had the original bosch, a set of bremi's and a new set of Bosch. I haven't swapped them and re scanned but it takes quite a while for it to even throw the misfire code.

if you have changed the coils and not the plugs, the problem might be in the plugs or the wiring to the coils - the wiring might be shorting... do you get the worsening condition when the car is under a load - say going full throttle uphill? in other words, regular driving, misfire, no codes, uphill under load - codes, and check engine light...
before going into the more sophisticated issues, as the shafts or whatnot, you should completely rule out simpler issues, like oil in the plugs, or shorting wire harnesses, or other electromechanical issues... Have you had a chance to reset the codes and see if they comeback? if you are doing this kind of work yourself, you definitely need INPA software package, sold by a dude from romania - many of us have bought it...

Could also be a bad injector. You need to isolate which cylinder is miss firing and go from there.

I have changed the plugs as well. It only does it under load it seems worse at lower speeds maybe 20 to 30 percent throttle but it does continue all the way through full throttle. It has never thrown a check engine light. I have taken it to a BMW specialty shop they couldn't get any codes from it. I hooked several other scanners up to it and it had no codes. I took it to BMW they were able to get a misfire code on two cylinders I don't remember what cylinders it was. They didn't want to go any further until I spent almost $1,000 with them replacing the coils and plugs I had just replaced because I didn't buy them from BMW although they are the Bosch coils. I have been driving it for a while. Still never throw. A check engine light. We recently just got a new snap on modis ultra scanner. I hooked it up and it is showing multi cylinder misfire. It shows cylinder 1 2 and 7. It also has a code 2a17 dmtl system error. I have been told possibly mass airflow sensor. Eccentric shafts, PVC system problems. We did also replace PVC valves. Not really sure where to go from here don't wanna just start throwing parts at it. I cleared the codes and drove it for a couple weeks Hooked it back up and it's not showing any new codes it seems to take quite a whole for it to throw the misfire codes although the misfire never stops.

Start with the basic, do a compression test on all the cylinder to see what condition they are in. If any of the cylinders are low compare with the other, do a leak down test to determine why the cylinder is low. Hissing noise in the exhaust is probably an exhaust valve, hissing noise in the intake manifold is probably an intake valve and hissing noise in the oil pan (remove the dip stick to listen for this one) is probably your rings.

One other thing I forgot to mention is that it seems to run good when it is cold if you start it up cold and drive away for the first few minutes it runs good.

^strange problem indeed. Did you clean the MAF?