Help Random Misfires 1999 323i E46

[bkpiper00]

I need help... I originally had emission codes that the shop thought was causing the random misfires P0420 & P430. The misfire codes were P0301, 304,305,306.

I installed new cats (headers) and O2 sensors and the emission codes are gone but the misfires still exist. They are random in the sense that you can reset the codes and drive it for 15 minutes and the they will show up and sometimes on different cylinders.

This is what we have done and ruled out.

Plugs are new, connector boots are new, Fuel pressure checks out. New oil and filter (BMW 5w30 full synthetic)new air filter as well.

I am stumped and out about $1800 so far.

Any help would be much appreciated.

Bryan

[zibby]

You need a set of new ignition coils.Buy OEM do not go for cheaper "no name" brands.
Misfire is on 4 of 6 cylinders ,but change all 6 of them

[DesertMotorWorks]

Originally Posted by bkpiper00

I need help... I originally had emission codes that the shop thought was causing the random misfires P0420 & P430. The misfire codes were P0301, 304,305,306.

I installed new cats (headers) and O2 sensors and the emission codes are gone but the misfires still exist. They are random in the sense that you can reset the codes and drive it for 15 minutes and the they will show up and sometimes on different cylinders.

This is what we have done and ruled out.

Plugs are new, connector boots are new, Fuel pressure checks out. New oil and filter (BMW 5w30 full synthetic)new air filter as well.

I am stumped and out about $1800 so far.

Any help would be much appreciated.

Bryan

Bryan -

Vacuum leaks are very common and can cause all kinds of hell. When dealing with misfires, a smoke-test for vacuum leaks should have been the first diagnostic procedure done (after scanning for codes). Sounds like whoever did the repairs was simply throwing parts at the problem, instead of diagnosis the problem properly.

[bkpiper00]

what about the misfires changing? I cna reset the codes and drive it and run the codes again and then I may get 1,2,3,4. Its happen twice so far. I have even replaced the #1 coil and switched it bto see if the bad coil moves with it. sometimes it does and sometimes it doesnt.

I just drove it and now I have o2 codes and fuel trim bank codes P0170 & P0173, P1188, P1189 and misfires in 1,2 3,4 not 5 and 6 now.

[DesertMotorWorks]

Originally Posted by bkpiper00

what about the misfires changing? I cna reset the codes and drive it and run the codes again and then I may get 1,2,3,4. Its happen twice so far. I have even replaced the #1 coil and switched it bto see if the bad coil moves with it. sometimes it does and sometimes it doesnt.

I just drove it and now I have o2 codes and fuel trim bank codes P0170 & P0173, P1188, P1189 and misfires in 1,2 3,4 not 5 and 6 now.

All those symptoms are very indicative of a vacuum leak.

[bkpiper00]

how do you do a smoke test? Can I do it or do I have o get a shop to do it?

If so any directions as to how?

[DesertMotorWorks]

Well, the least expensive way will be for you to take it to a shop...unless you want to dish out the dough to buy a smoke machine...www.redlinedetection.com - EVAP Smoke Machine, Smoke Pro Total Tech, Smoke Pro Diagnostic Automotive Leak tester finds vacuum and EVAP leaks Runs on baby oil Smoke Pro

[yalova77]

hey guys i have the same issues about misfiring.just did the plugs and i still have p0153 bank 2,sensor 1.i also add coolent once a week,and oil also 2-3 quart a month or so.mec. was suspecting blown head but still not sure.next i ll change the o2 and see what happens but u guys r being great help,thnx a looooot.