View Full Version : Missfiring on all cylinders.

06-27-2003, 04:38 PM
Hey Guys here is a puzzle for you that I’m currently dealing with.
I have a 97 M3 with 150K on it. I just had the vacuum pump, and an 02 sensor replaced along with a clutch fan - all done at Chucks (Thanks guys!). However it is the fourth day now and I still have a rough idle and missfiring on all cylinders and a faulted mixture (Chuck checked the codes on his computer). The idle is rough from 700 to about 1.5 rpm and occasionally rough idle continues up to 2~2.5. The check engine light is also on.

My guess is a vacuum leak - anyone else any ideas? I'm going to take a look at the plugs to see if there is anything funny with them.

06-27-2003, 04:49 PM
1 thing that could cuz missfiring is that, your wires coming out of the distribuer are messed up! and they don't go to the right sparkplug!.. go to a good mechanic they'll fix it for you in a minute!... there was this guy who could do that just by listening to the engine sound!

06-27-2003, 08:55 PM
i had this problem on my dads 7 series...

what it was...the catalitic converters contence had broken up and got stuck in the pipes causing too much back pressure and causing the cylinders to miss fire...

check it out...toss it up on a lift and hit the converters...if you hear a rattle you might have a winner


06-27-2003, 09:18 PM
thx guys! - anyone else?

06-28-2003, 12:12 AM
I openned up my 2 of the 6 plugs this is what they both looked like. I only posted one. should i have them swapped out for new ones? is the brownish tan normal?

Thanks for all your help

06-28-2003, 02:34 AM
are you using bosch platinum 4's? I heard problems with those and E36.. they get too hot or something.\

if you dont figure the problem out, you can take the car to Chucks auto, and ask for Charlie, tell him you are from maxbimmer. He can help you out.

06-28-2003, 02:55 AM

yes those are the ones. Actually my car has been in and out of there the past 4 days ... so tomorrow i'm going back to pick up the plugs and see what they do for me (but i have a sneeky suspusion that is a vacuum leak some where) If the plugs fix it great!!!

About the type of plugs - chuck is ordering them for me and he says they are specific to the m3. I'm going to pick them up tomorrow.

I'm sure they will be the same.

06-28-2003, 03:09 PM
Thanks for all the of help guys. I have managed to change all my spark plugs with bosch platinum 4s. I had my computer reset (of course with a little help from chuck again!!!, Thank you Thank you) and was able to get my car out and did a mixture of city and highway driving with slow and hard acceleration (to see if i could induce any misfiring like before) thus far everything seems okay (no codes no check engine light)

I still plan on doing the vacuum leak test. A friend of mine who has a garage has a smoke out machine - he said basically what you do is you take disconnect a hose tied to the cars vacuum system plug up one end and insert the machine nozzle in the other. The machine begins to fill the engine up with smoke (while it is off of course). If you see any smoke - then there is your leak.

I have attached a closer shot of my plug - they were pretty much due!

Thanks again all and have a great weekend!

The Sly
06-28-2003, 10:13 PM
WOW first time i hear of the smoke test...

One easy way to find out if you have a vacuum leak anywhere is .......
Use a propane torch little tank with a small hose, with the engine running
you crack open the propane and run it along the vacuum hoses and intake everywhere...if the engine revs up, then the propane is being sucked in via the leak and this make the engine rev up...

Now you just look closer to find the bad leak....on a hose or intake boot....