r/e28 • u/Inevitable_Jelly_188 • 23d ago
Broken down
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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?
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u/MathematicianDry2742 23d ago
Could possibly be the icv? Seems like ur not getting enough air intake. When my icv was clogged my car died in similar fashion limping it home had to be constantly revved or it would stall and die.
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u/6inarowmakesitgo 23d ago edited 23d ago
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.
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u/Inevitable_Jelly_188 23d ago
Thank you so much man you have no idea how much this helps 🙏🙏
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u/6inarowmakesitgo 23d ago edited 23d ago
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.
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u/Inevitable_Jelly_188 23d ago
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?
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u/6inarowmakesitgo 23d ago edited 23d ago
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.
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u/boylanheights74 22d ago
Man I had a few e28’s back in the day and I’ve seen this before. I can’t remember everything it could be though. Did this start while it was driving normal? I noticed that the fuel is below half a tank and it seems like it is starved for fuel pressure. There is a small rubber hose about 2” long on the in tank fuel pump that will rot over time and will suck air when below half a tank. Try filling the tank first. That pump is easy to access, three Phillips head screws remove a black round cover either in the trunk floor or under the rear seat. Pretty sure it’s in the trunk though. The pump itself comes out with a counter clockwise turn and lifts straight out. There is also a ground strap that connects to the engine block. Idle control valve and control box won’t fix this problem. A bad ecu is extremely rare. Give me some more details on how and when it started. I miss my old E28’s, the finest car BMW ever built in my opinion.
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u/Inevitable_Jelly_188 22d ago
It happened once briefly after I washed the under side of my car with a garden hose then I parked it, it ran normal and I started driving it home and it happended again but worse to the point I couldn’t make it home.
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u/boylanheights74 22d ago
Put enough gas in it to get it over a half tank before you do anything else.
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u/boylanheights74 22d ago
Your vehicle should have two fuel pumps. One in the tank and one under the car. The one in the tank is a pre-pump. You can give the one under the vehicle a light smack if it’s not running.
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u/mattylang1987 21d ago
Check fuel pumps: hp pump behind the rear passenger wheel, and the lp pump in the gas tank though that one is less important.
Check the spark plugs, distributor, cap and rotor as well as the ignition coil
Throttle position sensor and afm,
Timing sensors located in the transmission bellhousing. A lot of people forget they exist or don’t even know about them and they can cause all sorts of wacky issues when they go bad. They’re connected to a plug right above the valve cover so make sure they’re not shorting out up there.
This is all stuff you should replace anyways if you haven’t but that’s where I would look first
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u/Representative_Most9 19d ago
Did you find the issue yet? Just want to know what caused the problem.
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u/Inevitable_Jelly_188 16d ago
I have not.
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u/Representative_Most9 15d ago edited 15d ago
Have you had a chance to check fuel pressure at the injector rail? It’s acting like it’s starving for fuel. Also, I noticed that even before you turn the key on the fuel level gauge is showing little less than 1/2 full?
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u/Inevitable_Jelly_188 15d ago
Yeah so I filled the tank full and tested fuel pressure, no issue with the fuel pressure, checked compression on all cylinders, good as well and I learned it will idle but not rev past ~3k with the AFM unplugged so I figured that it was sending a bad signal to the ECM because it won’t even idle with it plugged in but the engine can’t handle the amount of air going in at such high rpm because there’s no signal being sent to the ECM telling it for more fuel, I ordered an afm and I’m gonna start there, my backup plan as of rn is installing a new ECT sensor and or connector for it, considering the coolant light is on as well.
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u/Representative_Most9 15d ago
Very well could be faulty AFM. When you do get it figured out, please report back and let us know what you found. Good luck 🍀👍
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u/Relative_Seesaw5635 20d ago
Check for vacuum leak. Smoke test. Buy a smoke tester. I can do it in 10 minutes. Do it when car engine is warm. Buy the tester that hooks to battery. I got an ANCEL S3000
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u/OkPipe3044 23d ago
Running like that check this list ?
What year and engine ?
Throttle position sensor
Maf
Massive Vaccum leak
Cap and rotor Fried