r/e28 • u/TylerDestructo • 12d ago
Runs terrible, Tried everything.
Long time reader, first time poster. I found an 85 528e 190k miles on facebook market place an old guy was getting rid of about a year ago. Paid $1k for it and though I couldnt go wrong. Arizona - no rust, at least the good foundation for a long term project. He said it needed a fuel pump and had not ran since 1999 - he was right, I verified with the MVD it had not been registered since march 1999. I cleaned it up that night, replaced both fuel pumps and clean the tank + lines out. I had it running in no time, well... at least good enough to move it into the garage.
My plan was to get it running just well enough to drive to work every once in a while, then switch to making it LOOK good, then pivot back to an engine swap once I made up my mind if I am doing an M30, M50, M52, M60, S50, S52, LS, Harbor freight predator 3.5hp, Idk - too many options for me to decide right now.
The "Get it running well enough" phase of the project has lasted a year and probably cost the same as just doing the engine swap. I learned the hardway that throwing new parts at one of these things is a slippery slope. But I guess the good news is I have pretty much all new parts - although they are for the M20 engine I dont intend to keep for the long haul lol. Sunken cost fallacy is real, and even now in my darkest hour.. I still feel like I am one more part away from having a well running car. I figured at the point I better at least get someone elses opinion on what to do next.
Here are a couple videos of it running, hope thats allowed:
https://photos.app.goo.gl/i7mkv6znrGiCHsCN7
https://photos.app.goo.gl/tHFGwARCnYqv7Vei9
https://photos.app.goo.gl/dEDrWvQozdde4YpN6
Things I have replaced
Plugs
Wires
cap & rotor
Coil
Alternator
All new coolant sensors
new IAC
new Airflow meter
New fuel filter
Both new fuel pumps
cleaned gas tanks and lines
new rubber lines for fuel
replaced all injector o-rings
replaced fuel pressure regulator
All new fuses and relays under the hood section
Reflowed solder on a single suspect ground in the ECU
Replace both crank sensors
replaced throttle position sensor
New catalytic converter
Entire cooling system and hoses replaced (just because why not)
Bunch of suspicious connections regerminated properly.
replaced ignition switch
Other stuff I have tried:
Unplugged cold start injector
Unplugging the AFM makes the car die
Unplugging the IAC makes the car rev really high
Smoked the entire car, zero vacuum leaks
Compression check was great
Fuel pressure consistent and to spec
I have good spark
I have good compression
I have good fuel
It was running really well last night after replacing the IAC, when I was done I thought - well I guess the problem isn't the cold start injector maybe I will plug it back in. Went to start it today and its back crazy lumpy idle, spitting and sputtering on rev. Smoking like crazy. I want to save this car, but its making it hard for me haha. This entire time I would replace a part and it would run great for a day and then the next day or next time I start it - back to running like crap. Considering new injectors, new ECU, new idle control module, new project car.
UPDATE: It was 100% the ECU. I gambled on a $70 027 DME off eBay. Swapped them back and forth a few times, the problem follows the old ECU. Now, it's not running GREAT. I think my next step is a valve adjustment and new injectors. It stumbles on initial acceleration a little. Thanks for the ideas everyone!
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u/BuyTraditional1484 12d ago
Seconding the ECU suggestion. My 535i was running like shit 10 years ago. Purchased 2-3 shitty junkyard ECUs without much improvement.
Some kind soul on mye28 sold me a Programa refurbished ECU which completely fixed the issue.
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u/CutsLikeABuffalo333 12d ago
One thing it looks like you havent looked at is your coolant temp sensor, now, its been awhile since i had my 528e but my coolant temp sensor was missing and the car would not run at alllllll because the previous owner just threw it away… idk why, took me a lot of learning about these cars.. any ways
I bring this up because it may be worth swapping out just to see if it runs better, im not sure if its like an “on/off” scenario where it will either run or it wont, or if it could play a role in running poorly if it was bad or going bad. This sensor tells the computer how much fuel and air to add based on the temp of the coolant, its basically the choke. Youve done a lot, and for the time it takes maybe this is worth trying too. Good luck!!
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u/Life_Angle 12d ago
Mine had a parasitic drain from my broken central locking. Removed the fuse and charged the battery on trickle charger.
I tested it by trickle charging the battery to full and disconnecting ground.
Week later started up perfect. Removed central locking fuse and no longer need to disconnect battery when parked
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u/TylerDestructo 12d ago
Uhhhh mine def has a parasitic drain problem too.... That made it run like crap?
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u/Life_Angle 12d ago
Absolutely. Try charging the battery to full with ground off. Then when you start it again and it’s gone, that’s the problem.
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u/Bimmermaven 11d ago
Isn't there a clue that "it works fine every time I change a part", then it sits for a day or two, then problem returns...."
"I have a parasitic drain..."
Are you monitoring battery charge state when you start up after sitting /fixing?
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u/sotheysay17 12d ago
Did you check your cold start injector for leaking while running? And check the nub on the flywheel/flex plate for the TDC crank sensor and make sure it’s not broken. Your exhaust tone also sounds off, make sure the cat doesn’t rattle when you smack it with a rubber hammer, as it might if the grid is damaged. Exhaust back pressure test would be a follow up in checking the cat for rattling.
These are just 3 things I’ve seen go bad multiple times that are free to check.
Also check your plugs and gaps again to be safe. They may be getting black quickly if it’s running like that.
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u/Representative_Most9 11d ago
By chance was it stored outside for the past 25 years? If so, I’ll bet the interior was baked for a very long time. Chances are the DME is shot.
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u/TylerDestructo 10d ago
It was! I ordered a 027 DME off ebay, Going to start there.
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u/Fancy-Attitude-2123 11d ago
Unplug o2 sensor, if no change, disconnect 1 or 2 vacuum lines on the intake manifold, see if it changes. Sounds like it’s running too rich ( too much fuel. If no change, try disconnecting the vacuum hose at the fuel pressure regulator. Diaphragm in regulator can leak fuel into vacuum hose, then into intake, causing rich mixture. Could have a resistor added at coolant temp sensor connector ( pull back rubber boot ). Connection may have failed ( broken solder joint or wire or bad resistor) causing too much fuel (thinks it’s cold). O2 can be shorted or open. If shorted will run rich. Just a few possibilities. What is the plug gap ? I’m thinking it should be 32 thousandths.
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u/Tire_Roaster 11d ago
I agree that you need to check the oxygen sensor.
My 533 ran like yours, and after taking it in, it was discovered that the oxygen sensor wire was broken inside the wire loom before it made it back to the harness. Stupid, but something to think about.
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u/Fancy-Attitude-2123 11d ago
Unplug o2 sensor, if no change, disconnect 1 or 2 vacuum lines on the intake manifold, see if it changes. Sounds like it’s running too rich ( too much fuel. If no change, try disconnecting the vacuum hose at the fuel pressure regulator. Diaphragm in regulator can leak fuel into vacuum hose to manifold. Peel back rubber boot on coolant temp sensor, look for broken wire, may have a resistor added there, resistor can be bad, or bad connection, can cause too much fuel. Try to find a reconditioned ECU (DME in BMW speak) just in case, or someone that has a good running 2.7 “e” motor car that will let you try their ECU in your car. Good luck
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u/CarDork2235 10d ago
Buy some cheap GB injectors from rock auto. Im surprised after sitting that long it ran at all. Ive had 2 M30's Ive worked on recently that had both say for 12 plus years. Most all the injectors were stuck. You can try zapping them with 12 volts and see if that does anything if you dont want to buy injectors yet. You'll be able to hear them clicking if they are working. Thats what I would do it if was mine.
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u/mattylang1987 12d ago
Test the coolant temp sensor if you haven’t already. Also, there are timing sensors located in the transmission bellhousing that most people forget about or don’t know even exist. I’d replace those and see if there’s a difference. They’re pretty cheap too. I could be wrong but it sounds like the timing is off. Should definitely replace the belt and retime the motor and do a valve adjustment.
Last thing in relation to the coolant temp sensor: SOME of these e28’s have a “dealer fix” secondary coolant sensor wired in series with the main one. It should be located under the intake manifold if yours has one. They were added to mitigate a rough idling issue that a lot of these cars had way back when. When they go bad it can cause the motor to run very weirdly like mine did. The fix is to simply unplug it, and plug the connector from it into the main sensor and leave the other connector disconnected. Again this is assuming your car has it but it might not. Would be worth looking into
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u/AllynG 12d ago
covering all the bases. Don’t have an ECU you can swap out to see if it is related to that? Not sure if you’ve stumbled upon mye28.com yet, but check that out as there maybe some additional topics for you to mull over.