M42club.com - Home of the BMW E30/E36 318i/iS

DISCUSSION => Engine + Driveline => Topic started by: kurtf114 on August 15, 2010, 02:04:44 PM

Title: Severe Misfire
Post by: kurtf114 on August 15, 2010, 02:04:44 PM

A couple of weeks ago while driving, my 318 started to run terrible. It had no power, smelled terrible, and sounded like a Subaru STi.
After looking at it, Cylinder #2 and #4 are completely not firing. We checked the wires, and plugs and they're working fine, except every cylinder gets spark expect for cylinder #4. My coil pack was looking pretty haggard so I went out and bought a new one. Still no difference, and cylinder #4 was still not getting spark.
I checked the injectors also and they're also working.

Any ideas of what this problem is/ what I could check?
Its a 95, and the motor only has about 80k.

Thanks for any help

Title: Severe Misfire
Post by: KenC on August 15, 2010, 04:17:31 PM

Swap in a good DME and recheck.

Title: Severe Misfire
Post by: DesktopDave on August 16, 2010, 09:13:45 AM

Don't mean to be a jerk about this, but you do have the coils & wires correct, right?  Coil harness 1 goes  to coil 1 which goes to cylinder 1, right?  Wired 1-2-3-4 from rad to  firewall?

Ken is right about the DME too.  The early e36 had a problem with plugged water drains in the passenger-side plenum.  Pull the little elephant trunk & see if it's clogged.  If you had a recent storm or power wash the plenum floods the DME and makes it unhappy...  Pull the DME and check it - the case shouldn't have any evidence of water at all.

Run a stomp test too.  They're cheap & might be helpful.  Check the cam & crank position sensors next...cam must be about 1200 ohms, crank 600 or so.

Then test the other components one by one.  Coils are hard to test, but you've swapped them already.

Title: Severe Misfire
Post by: kurtf114 on August 16, 2010, 09:59:18 PM

Yeah, the firing order is all correct.

I actually pulled the DME today and there was no sign of water.
I will check the camshaft and crankshaft sensor tomorrow.

thanks

Title: Severe Misfire
Post by: xsjado on August 20, 2010, 02:36:59 PM

same thing happened today to me while driving my e30(e36m42)...suddenly just  sounded like 3cyls firing...goona check it out tomorow,hopefully it nothing expensive

Title: Severe Misfire
Post by: DesktopDave on August 20, 2010, 10:04:08 PM

Each of those coils is grounded by a big transistor in the DME.  It's unlikely, but possible that one or more transistor has overheated and failed due to wiring shorts or a bad coil.  In that case the transistors and coils both die a mutual death...adding a new coil will not fix the problem, and may even damage the new part.

Did you get any results from a stomp test?  It's easy & free.  That might help pinpoint what the DME thinks is happening.

Title: Severe Misfire
Post by: xsjado on August 21, 2010, 02:10:30 AM

i have spark i have fuel...now for compression test....OMG ..expensive...should port the head if everything needs to come out....