E46 Rough Idle and stalling fixed.
Hey all,
BLUF: 1 Bad coil made it seem like the car was falling apart.
I thought that I'd post a quick fix for you all. My wife's car is a 2003 325ci (coupe, not convertible) with an automatic. The other day it started to run really rough at idle and would stall when shifting from Reverse to Drive and when starting from a stop. My first thoughts were Idle control valve, Vacuum leaks and Vanos. I was completely wrong on all counts. I tore apart the complete intake track looking for vacuum leaks, found none and put it all back together. Ran the same. Then I got smart and hooked up my INPA setup. There we about 20 codes. Cleared those out and got back about 5. There wasn't a single code that really tipped me off, most were O2 sensor codes and enrichment and catalytic converter codes. Then I looked into the "rough" display and noticed that cylinder 6 was running way rough. I swapped the coil from Cylinder 6 to cylinder 1 (these are paired cylinders in the I-6 orientation). The Rough running numbers followed the coil. Bingo Bad coil. Next morning I went to the LKQ, bought 6 used coils, swapped it out. Cleared the codes, cleared the adaptions and it ran beautifully.
Total cost of parts.... $11. $9 for the one coil I needed and $2 entrance fee. I also picked up a bunch of stuff that I didn't strictly need, but wanted.
Moral of the story: Always go for the most likely and cheapest solution first and troubleshoot to determine the problem before jumping to conclusions and throwing parts at it.
This thread is useless without pics of dead coils.
Last edited by mynameisBMW; 10-29-2018 at 09:57 PM.
Reason: added bluf.
- E36 328i black - Steel adjustable rear lower control arms, Bridgestone RE-11
- E46 325ci white
Bookmarks