misfire, idling & under load, but not decelerating

[MysterE30]

Ahhhh!! I am having pretty much the exact problem! I don't know what to do. I just replaced the fuel pump and filter they weren't the problem. New plugs did nothing. I'm thinking gunked injectors, maybe fuel pressure regulator? Any other ideas???

[quikveedb2]

i hate to revive this thread from the grave, but i'm still trying to resolve this issue. the car has not seen much action since i've been too busy working, but the few times i have driven it the problem has been getting worse. that car runs better cold than hot, which is weird, and the "misfire" seems to be getting worse as well, i.e. missing on 2 instead of just 1 cylinder as the car warms up. it is also worse when it is damp or raining. i finally got a multimeter so i can start checking electrical stuff, where should i start?

[jlevie]

The DME runs a richer mixture on a cold engine. That could compensate for an intake leak, fuel system problem, or problem with the AFM that becomes significant once the engine is up to temperature.

I'd have the intake smoke tested as a diagnostic for an intake leak and I'd run the suite of fuel system tests documented in the Bentley for starters.

[quikveedb2]

cool, thanks, i'll start there.

[slo325i]

Maybe timing belt skipped?

[quikveedb2]

yeah but it runs great when cold, a skipped timing belt would run crappy consistently, no?

[Alphamale]

You may want to take a look @ the connections of the engine harness plug underneath the manifold. Take it apart and see if there are any shorts/water/derbis..etc. Clean that stuff up.

[transatlantic0207]

I thought I'd revive an old thread instead of starting another...so fuck off search nazi's!

Quik, what was the result of your findings?
I am having the same problem, no check engine light yet but WOT in any gears will misfire a bit then smooth out....it's getting progressively worse and I have no idea what to do next...I am waiting for a new AFM though so after that i'll update

[quikveedb2]

i've been all over the place with this fix, but i've been following this thread:
http://r3vlimited.com/board/showthread.php?t=144867
and the breakdown of the fusion between the front & back of the harmonic balancer seems to be the culprit, as 2-3 others with similar issues have fixed the misfire by either replacing or reattaching the 2 parts of the balancer. it seems the front, toothed part can move if the rubber connection breaks down (as seems to be becoming more common with age) and thereby causing the dme to get an incorrect reading on engine position, thereby timing the ignition event incorrectly. i'm gonna replace a few other parts i mentioned in the other thread tomorrow, and try to reattach the 2 parts of the balancer or at least check for proper alignment & eliminate it as a factor. this issue has been progressing slowly for the past 3-4 months for me.

[transatlantic0207]

I've been following the same thread and I posted in it...I thought I fixed it by fixing a major vaccum leak with the charcoal cansiter purge valve not being connected but it reared its ugly head again this afternoon

[transatlantic0207]

I have an extra dme (yellow 380) I'll try..its from a newer car, so we'll see how it that works out!

[quikveedb2]

yeah let me know how that works out for sure! i'll post updates as soon as i get around to messing with the balancer.

[quikveedb2]

never mind the balancer, i finally fucking fixed it! there was a crack in the bottom of my distributor cap and i'm thinking i was getting some arcing from one of the poles in the cap to the mounting bolt nearby as that's where the crack ran, roughly. the old rotor tested high for resistance as did the coil for primary resistance. replaced all 3, and she runs like an absloute champ. at least i know i've got a good strong spark now (and a shit ton of new parts in my motor.) i do have a bit of loping at idle, but whatever, i'll tackle that next.

words cannot describe how relieved i am to be rid of that damn misfire! i'm gonna go try & get a speeding ticket!