85 325e No Start/Rough Idle/Misfiring

[fartingfool]

Summary: The car ran great for the longest time, then started to develop a misfire under acceleration. This progressed into being able to drive the car by feathering the throttle and it worked out for weeks as I slowly diagnosed the problem. Then while accelerating one day, I got a loud backfire in the exhaust and the car refused to start for a couple days.

I got the car home, and it started up again. The car was semi-drivable (complete lack of power, misfiring), and now after some further diagnosis and replacement parts (described below), the car refuses to start now.

I discovered that after trying to crank it over one last time, the intake boot and throttle body were full of fuel; and with this note I am at a loss and need help.

I have replaced everything short of replacing the engine, and the problem still persists.

Symptoms: Initially lack of power, misfire under power. Then backfire, stall, no start. Ran after no modification, but discovered an immediate misfire (and backfire in the exhaust) at wide open throttle to 2500rpm then let off, bang.

My crank sensor connector was broken, I tested resistance and it was within spec (minus the 100k ohms from signal wires to shield wires). I noticed that as I measured the resistance of the two signal wires (the ones you get an AC voltage from) with the engine running, my car's idle would rise as I measured the resistance. As soon as I removed the probes the idle would go down. The rise/fall was about 50-75rpm. However, on two occasions while measuring the crank sensor resistance, the idle would stay up after removing the probes and the engine ran perfectly until I shut it off. After successfully repeating that twice, I decided to replace the sensors.

After I replaced the crank and speed sensors, it ran for 30 seconds, stall, no start since.


I do have spark and fuel.


Replaced/Changed Parts: Fuel Pump, swapped DME, checked plugs/wires/ignition system, brand new Crank and Speed sensors.

Relatively (and relevant) new items on the car (<1 year): Fuel injectors (cleaned and flow tested), fuel filter, ignition coil, cap/rotor (more I can't free recall)



I'm willing to take any and all suggestions even if I've already tried them, I'm just fresh out of ideas and things to check. If you have any idea, I'm all ears.

Thanks

[fartingfool]

I went and setup a pressure gauge to the car. It's reading where it should be (2.5 bar, 37~psi) and as defined by my fuel pressure regulator. I swapped the fuel pressure regulator with a known working one. After installing all of that, maybe because the engine was able to de-flood, I got it to start. I haven't been able to replicate the flooding since and the engine seems to start semi-reliably now.

When the engine was bone stock cold, I was able to almost full throttle it right before it would cut out, idle rough, then stall. Now after it's semi-warm, it will idle poorly, then stall out.

http://www.youtube.com/embed/E3WvUX5N7Eo
The motor doesn't sound nearly that tinny/dieselish in real life.

I also checked the cold start injector, no fuel is coming out at all (I removed it from the intake, but left the fuel line and wires attached in a bucket). What conditions make this injector fire?

[bastianshaw]

my car has the EXACT same problem missfires under acceleration but it desnt sound as advanced as yours im running a JC chip are u chipped?

[fartingfool]

I was, but the problem still persists with an entirely different ecu.

I ended up checking all of my sensors at the ECU and idle control module and they all came out fine as far as the bentley and I am concerned. Right around as I was finishing up, I heard a loud squeal from the engine bay and smelled burned rubber/oil and could see smoke fuming out from my intake. I checked my accessory belts and those were fine, so..

I took off the timing cover and found these images.

The tensioner has a bit of lateral play, I can feel/hear clicking when I wobble it, but not necessarily see any. There is also a "rolling" sound inside that sound like the bearings are going out. There also appears to be little spots of melted rubber sporadically on the tensioner wheel. I'll upload some pics/videos of that when I can for other's future reference.

Opinion of the pictures and the timing? Don't forget about the youtube video of the exact problem.

I replaced the belt and tensioner and made sure the timing was EXACT, hell I rotated the motor prolly a dozen times by hand to be 100% sure I still was. Before I hooked up the waterpump/alternator/air conditioner belts, I cranked over the motor to fire it up and it worked flawlessly. I ran it for about 1-2 minutes, it responded exactly like a well-running m20 should.

I came back a few hours later with coolant, tidied up a couple loose ends like the belts and fan, fired it up and it was running like a dog again.

The problem is still there and I'm about at the point of taking it to a shop to have them diagnose the problem and go from there about the cost analysis of having them fix the issue versus me with their diagnosis.