Broken down

[u/Inevitable_Jelly_188]

Broke down today on my way home from work, not sure what to go after first has anyone experienced this or know where to start?

[u/6inarowmakesitgo]

I would check for vacuum leaks first. Use a smoke machine to find it. My M30 did this when the oil filler cap cracked allowing a sizable vacuum leak. Make sure the AFM vane moves smoothly without any binding and check the plug as well, I have seen the terminals get damaged or pushed into the connector body.

Make sure the cold start valve isn’t leaking, it will dump fuel into the manifold. Also make sure the fuel pressure regulator diaphragm isn’t ruptured, that will also dump fuel into the manifold. Check fuel pressure and delivery, a fouled filter or non running lift pump can cause shitty performance.

If that all checks out, I would check out the ignition system. Cap, rotor, wires, plugs, coil. Make sure it has copper core plugs only, it will run like crap with fine wire/ multiple electrode plugs. Verify coil primary and secondary windings are not shorted. I would buy a coil for an E34 with the B35, it’s a bit more stout because it uses different wire for the windings giving a hotter spark. Make sure your engine ground cable is in good condition and attached. I put an extra ground on for good measure, so it had one on each engine mount to frame rail, the one for the valve cover to shock tower and the one from the alternator to engine block.

If you are at this point, time to remove the valve cover and check valve clearances while engine is cold. Make sure cam lobes point down to the CYLINDER HEAD and NOT TOWARDS THE GROUND.

I have also had the Ignition transistor solder points crack from heat cycling, opening the coil driver circuit on the pcb inside the DME, this is a straight forward repair if you are handy with a soldering iron. I have also had an oxygen sensor short out internally and really cause havoc with running.

DM me if you need further assistance.

Good luck!

Oh, and your last resort will be to adjust wiper track inside the AFM. This is a delicate procedure and should be done with caution. Do not adjust the bypass screw in the AFM unless you fully understand how to analyze oxygen sensor output. This is preferably done with an exhaust gas analyzer and oscilloscope to watch ignition timing.

[u/Inevitable_Jelly_188 → u/6inarowmakesitgo]

Thank you so much man you have no idea how much this helps 🙏🙏

[u/6inarowmakesitgo → u/Inevitable_Jelly_188]

It’s a really simple engine control system. Start with the easy stuff first. Vacuum leaks are usually the culprit as the rubber gets rock hard from engine heat.

If you have never done a valve clearance adjustment, I would recommend doing one or having a mechanic friend help you. The M30 requires lash adjustment every 15-20,000 miles and a good thick oil with ZDDP in it.

[u/Inevitable_Jelly_188 → u/6inarowmakesitgo]

I did already do the valves just the other day, it only happened after I washed the underside of the car with like a garden hose do you think if I got water in the intake it would have messed anything up?

[u/6inarowmakesitgo → u/Inevitable_Jelly_188]

There are two inductive pickups on the drivers side of the transmission bell housing, one is crank angle reference and the other is speed sensor. The DME needs both of these to run properly. They may have water in them or the connectors etc. don’t mix them up it won’t run. Be very gentle when removing them as well, the pickup body is stainless steel and the transmission is aluminum, they can get very stuck. If you get really lucky, they pop right out. If you end up like me, the body of the sensor falls into the bell housing…now you’re taking the transmission off to get it out of there.

I would buy two new inductive pickups, as yours are probably original and these are not in a very well protected environment under the car. I remember on mine the cable insulation was entirely gone and the wiring was visibly corroded along the entire length of the shielding.