Severe misfire. NEED HELP

[derpderpe30]

Thanks for looking at my thread. I have an 85 325e that ive had for about a year and a half now. Ill start out with what ive replaced...
Both fuel pumps
Distributor cap and rotor
tps
ignition coil
checked vacuum leaks
crank sensor
cleaned iac
timing belt and tensioner
fuel pressure regulator

The car has been great, however for the past 6 months developed a very intermittent misfire. At first it wasn't too bad, just come up once a week or so, but in the past 2 months it has been so severe that I cant even drive the car without it stalling out. The problem is that it will run like its on 3 cylinders and then out of nowhere run perfectly fine for around 5 min almost like clockwork, then it will start to choke itself out again. I'm a mechanic myself, but with work and other commitments its hard for me to find time to diagnose this myself and I need my car back. If anyone has any kind of feedback please comment. I want my e30 back!!!!!!

[TobyB]

Take apart the big connectors and check for corrosion.

Check the smaller of the big wires coming off the battery CAREFULLY
to make sure it's not loose, corroded or broken.

Check the big ground from the block to the body.

hth

t

[e30onBBSs]

haven't replaced the plugs? Look at them at least and see if they are bad. One time on our mini the metal piece of the plug that the spark hits broke off and made a horrid misfire after 3k

I would also check the spark plug wires' resistances

[EatsHondas]

Have a look at C191, the round connector underneath the intake manifold. The fuel injectors' wiring runs through there. Running on 3 cylinders intermittently could mean one of the two injector banks are cutting out.

[betsy325e]

I had a similar problem to the one you described. My TPS connector was sort of half-on the TPS. Never had it fully stall out, though. The intermittent nature would suggest it's something silly like a bad connection.

As suggested above, check the wiring at the connections and check your grounds, especially G103 (on intake manifold behind diag. port).

Does it do it long enough to get out while it's running like a beast and have a peek under the hood?

[betsy325e]

C101 is mounted on the firewall.

C191 would be located under the manifold and would have fuel injection wiring running through it. However, OP has an 85 325e, so he ain't got that.

Let's not add fictional bits to this man's already difficult troubleshooting haha.

*just tryin to keep the cognitive load down.

[master quon]

In my experience, when the issue is sporadic like that, it's usually electrical. When i first started working on cars, i changed the distributor cap and rotor. I accidentally broke one of the ignition wires when pulling it off the distributor cap. I didn't notice it, and it ran fine for a while then had the same issue as you. The gap where it broke got wider and the electricity wouldn't jump the gap any more.

I also recommend doing small cleaning work like cleaning sensors and grime, wiping down wires, throttle body, etc. I sometimes find doing small stuff like that can help you find what you're looking for (and sometimes cause more issues by accidentally breaking things haha). But you're reconnecting plugs, something could be loose, and you get a visual of whatever is wrong. Plus clean engine bay! That's always good.