I'm the new owner of a 1995 940 with 150,000 miles and it's also my first car so I don't really know what I'm doing yet. This is also my first post so hi.
It has a B230FD with the EGR stuff (annoying because the PCV box looks clogged (covered in gunk) and I'd need to take the EGR valve off to get to it i think.) And M47 transmission.

It's been misfiring at low RPM and sometimes dying at idle, and I'm hoping anyone with a little more than my zero experience might be able to point me in the right direction.
Feels like its on 3 or maybe even 2 cylinders (exact same interval between power pulses) until the revs get up (2000ish) then suddenly it has full power again, so I've been trying to figure out why. Seems to run on all four when I start it up, and usually fires up immediately (sometimes it really struggles though).

So far I've only changed the sparkplugs as they had some gunk on the end when I checked, went for a drive and was fine for 5 minutes then the misfires returned.
I've listened to the injectors with a screwdriver and they all seem to be working the exact same, but they look very dirty (mostly black on the yellow injectors) so not sure if they might be clogged somewhat.
Intake manifold and throttle body look very dirty inside so going to take those off and clean them I think, will let me get to the PCV box easier also. (because oil seems to be leaking from the valve cover so think I should probably clean the PCV out)

Also noticed that I can see into the distributor through a little gap and see it sparking, is this normal?? Surely that would just let water in very easy, but I took it off and it seems undamaged and looks identical to a replacement (its a bosch one).
I've attached a picture of it.

I've read lots of different posts about other people with similar issues, so here are the main things I'm suspecting.
- Too much or too little fuel (my FPR vacuum hose smells like fuel)
- Vacuum leak somewhere, I haven't checked properly yet as I don't really know how to.
- Crank position sensor, haven't looked at mine yet going to do that soon apparently the insulation just falls apart.

- I don't think it's a spark issue I've checked all the leads with the new plugs.

I've driven it a few thousand miles since I got it a few months ago and these issues appeared fairly suddenly, started with it forgetting how to idle when stopping in neutral a few weeks ago and has been getting progressively worse since then.

Anyway thanks for reading and if you have any insight I would greatly appreciate it. I love this car and want to get it back on its feet.
Happy to provide more info if needed :)

 

Update
Took the distributor off and the contacts had lumps on them they'd corroded that bad, so sanded them clean until I can get a new one and that seemed to have solved my issue.

I know now I should have probably checked that first, but whatever, I learned a lot by fiddling with everything else

dirty

need a new one but will do for now

Still confused on if I should be able to see into the distributor as I can't find any info about that.

 

Goldenblock here! Senior Member
I'm glad your car made improvements
If you need any good tested used parts
Hit me on Atlanta Craigslist
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Have a lot of Bosch Cap and rotors too.

 

I had a similar misfiring/low power condition with my own B230 in an 87 740 version and found that the distributor mount was loose. After cleaning the cap and tightening, It seemed to resolve the misfire condition and developed better power.

 

yes you can use emory cloth or fine sand paper to clean the rotor and cap contacts. My suggestion is if the car is new to you also check the date codes on the wires - if over 5 years go new wires/plugs/cap/rotor. Also inspect the connections to the coil and battery posts. clean and tighten as well. As to plugs, go OEM - older engines with single coil ignitions can't really use newer plug types so stick with copper core and make sure they are properly gapped and the correct part# for your engine.