E30 Rough Running, Engine Mystery

[Danny 86 325es]

I'm the proud original owner of a 1986 325es, which I'm currently fixing up in preparation for handing it over to my 16 year old son, who's promised me he's going to keep it stock and not do anything too wild with the wheels or paint job. Before handing my baby over, I had some repairs made by my mechanic brother-in-law (BIL). Before the repairs, my car ran great ... no problem starting, no misfiring, smooth acceleration, etc. Then, I asked BIL to repair some long-standing nits with the car: (a) slow oil leak from upper and lower engine gaskets; (b) replace radiator and related cooling system components; (c) switch over AC system from R12 to R134; (d) replace clutch assembly; (e) replace odometer gears; (f) replace instrument cluster SI Board (which I got from Pelican, but which didn't fit, but that's another story).

BIL said that since he would be taking the engine out, we might as well change various belts and hoses. This included the timing belt (he also got a new rotor cap, new coil, new wires, new sparkplugs). I said great, let's do it.

The problem is that after taking everything apart, replacing old parts with new parts, and putting everything together, the car is now a ***** to start, and when it does start, it's running very rough, like it's not firing on all cylinders, or that the timing is off. BIL was stumped, and brought in some of his other mechanic buddies to troubleshoot this problem. Here's what they did:

1. Double and triple-checked that timing alignment on the cam/rotor to make sure the lines lined up at TDC;
2. Checked the spark plugs -- the new ones had 4 prongs and had a weak spark, so they went back to the single prong plugs and made sure the gap spacing was to spec;
3. Replaced the rotor button;
4. Replaced the rotor cap;
5. Replaced the coil;
6. Checked for vacuum leaks;
7. Checked the sparkplug wires for any breaks;
8. Took apart the spark plug wire harness to double check that the right numbered wire was connected to the right number cylinder (1 thru 6 from front to back);
9. Did the ""dollar bill"" test at the exhaust to make sure there was no ""suction"" from faulty valves or whatever;

Everything checked out. Timing was aligned. There was fuel. There air. There was spark for all the plugs(much stronger after the coil replacement).

Here's the mystery: The engine does not start when the spark plug wires are connected to the rotor cap in the cylinder # sequence stated in the Manual -- 1, 5, 3,6,4,2 (this is also the sequence that BIL found on the All Data system). The engine also does not start when the wires are connected to the rotor cap in the sequence printed on the Bosch rotor cap cover which, I think went as follows -- 2,4,6,3,5,1. Rather, the engine starts and runs roughly when the wires are connected to the rotor an together different sequence, which I can't remember right now.

Any idea as to what's causing this weird situation and how to fix it? BIL did some more digging and discovered that some of the wires in harness connecting the computer to the fuel injectors had burnt through their plastic casing. He thinks that when they disconnected the harness wires from the fuel injectors in order to remove the engine, the physical act of moving the harness out of the way may have caused the burnt wires to touch each other, thereby causing the weird cylinder, spark plug, rotor cap connection/firing sequence. So now he's in the process of manually trying to repair each wire by soldering the burnt areas and re-sealing with some sort of shrink wrap.

Anyway, just wondered if you concur with BIL's diagnosis or whether they may be some other lurking problem that he hasn't thought of. Thanks!

[Danny 86 325es]

Update from BIL - He fixed about a dozen wires from the engine harness and hooked everything back up to the fuel injectors and other parts of the engine.

Good News: The car starts immediately and idles smoothly.
Bad News: When he presses the gas pedal, nothing happens ... the engine remains smoothly at idle and nothing else.

Anybody out there know what's going on with the engine?

[87 BMW 325]

Hey, sorry to hear about your troubles. I fixed my rough idle, rough through all RPMs, and rough start-up by doing this one simple thing. It was caused by my FUEL AIR FLOW METER (13-62-1-466-357 : $515). Pretty expensive. The good news is it didn't cost me a thing!!! I repaired mine and I'm sure you could too. I have posted a link that someone else made for you to view, but you don't have to go thru all of the details. (When you get the black plastic cover off, just push with your fingers on the metal "clip" to bend it a little and you are ready to go!)

All of this will make sense when you see the video. Basically, there is a metal piece that moves every time you push the gas petal down. It tells the car how much fuel to mix with the air to make the car run right. This metal piece wears groves in the sensor and all you have to do is move it a little to get it out of the old warn grooves to a spot that is like brand new. Check it out here -----> http://youtu.be/-11J8XawQtc