88 528e Auto Trans

[Electron]

My first German car, a 1988 528e equipped with auto trans. It has 188354 miles on it at the time I bought it from a friend of mine, who bought it in1989. He didn’t want to sell it to me because of the fact it has some problems. I said to him, problems…I have been driving American and Japanese vehicles for 37 yrs. err let me rephrase that, I have been working on American and Japanese vehicles for 37 yrs.
Two months I worked on him to sell this car to me, as he poked around and bought this part and that, trying to fix it. Well it’s mine now, and here I am asking for help. The main problem (aside from the water leak in the trunk and a few burnt out bulbs) is a problem with how it runs, or fails to run properly after it reaches operating temp.
Here are the symptoms, runs fine cold, but after reaching operating temp.it cuts out at exactly 2000 RPM. (Almost like a rev limiter)This symptom occurs at any road speed or engine load. Runs fine under 2000 RPM, but soon has the tach hits 2000 RPM …WHAA…BOG…WHAA…BOG…WHAA…BOG If I mash the accelerator to the floor it seems like the engine returns to idle and the trans drops into neutral, let off the gas then every thing is fine. As long if I keep it below 2000 RPM.
I think this car has a lot of life left init, but below 2000 RPM, that’s not much of a life for me. Any guidance you can provide is greatly appreciated.

Here’s another E28 with same problem , but I couldn’t find the any posts about what he did to fix it.

I have an '82 528e that I have been wrestling with for several weeks now and
am in need of ideas. I presently have the car at a very reputable BMW repair
only shop in Augusta, GA and they are also stumped.
The symptoms: Starts fine, idles fine, runs great up to 2000 rpm, then cuts
out and has basically no power. Gas mileage is awful.
What we have examined so far: Fuel pressure and flow rate - OK. Coil, plugs,
wires, condensor, rotor - Checked all OK. Air mass flow meter - put in good
one to test - No improvement. Motronic brain - put in a good one to test - no
improvement. Fuel injectors - put in good ones to try - no improvement.
Vacuum leaks - None. Catalytic convertor - checked but not stopped up. O2
sensor - Checked OK. Speed sensor and TDC sensor - checked OK, but could be
going bad at higher rpm; will replace next and then try. Throttle switch -
checked OK.
HELP! What else could be the problem? I have pretty much run out of options.
Andy Sparks
Thomson, GA
'82 528e

[njtech]

have you checked anything yet? You should always start by eliminating the basics, plugs, wires, cap, rotor, fuel and air filters, vacuum leaks. How is the fuel pressure/flow? Is the coil dying when it gets hot? Then move on to things like the maf, tps, ref sensors and such. HTH

Steve

[Electron]

Njtech, thank you for the reply. I bought all the tune up stuff, but I want to nail down this problem 1st before any maintenance work is performed. It’s not a random misfire, but like the engine computer is commanding a fail safe mode, or limp home mode at exactly 2000 RPM. My best tool at this point is information. This is what I have in my tool box so far;
Mr. Sparks made a post in another forum back in 1998 stating he has his 82 528 in a BMW dealer with the same symptoms as my 88 528. Here are the things that Mr. Sparks tried to fix his car.

What we have examined so far: Fuel pressure and flow rate - OK. Coil, plugs,
wires, condensor, rotor - Checked all OK. Air mass flow meter - put in good
one to test - No improvement. Motronic brain - put in a good one to test - no
improvement. Fuel injectors - put in good ones to try - no improvement.
Vacuum leaks - None. Catalytic convertor - checked but not stopped up. O2
sensor - Checked OK. Speed sensor and TDC sensor - checked OK, but could be
going bad at higher rpm; will replace next and then try. Throttle switch -
checked OK.

So what did Andy Sparks do to fix his car? I couldn’t find any reply, or any fallow up that supplied any clue to what he did to fix it. The question is what engine management event takes place at exactly 2000 RPM?

[e30fanm3]

disconnect the idle control valve and see if that helps

[Hoppy's535i]

528 redlines at 5k.

im willing to bet your having fuel flow problems. could be the pump?

run the car with the hood open, and give it a little gas via throttle body. go slow. and listen to see if the engine slowly fails or fails all at once. slowly = fuel pump or line
all at once = computor

[CiscoKid]

it is probablly the torque converter.

I believe that at 2000, the torque converter is completely out, and it sending all engine power to the wheels.

[Electron]

Thank you to everyone who responded,
I think I got figured it out. Friday I cut out of work early, to wash my new car. I let it idle while I washed it (10 min.) when I drove home; the 2000 rpm shut down problem was present for the 8 mile trip. In my garage I performed an experiment. Measured the crank sensor temperature while the engine fails to go past 2000 RPM. 118 degrees f. cooled the sensor down with ice cubes to 70 then the engine ran past 2000 RPM with no problem.
Repeated the test. Same results. I have a crank sensor on order, when I confirm the failure of the sensor as my cause, (the engine cuts out @ 2000 RPM) I will post it here.

Bryan

[Electron]

fixed it! The crank sensor was not the problem; turns out the TPS (throttle position sensor) would fail to switch from idle position. Under hood temperature was critical in the TPS failure. With the engine at operating temp. & with the hood open TPS worked good. Close the hood, five minutes later TPS failure.



I hope this helps someone out.



Bryan

['89 635 csi]

Thanks for letting us know!

[bryan1970]

hmmm thast interesting i would have never really thought temperature would have that much affect on a sensor like that. thats good knowledge to know thanks for posting the fix.

[Electron]

Bryan1970,

I was thinking the same thing, so why throw away a perfectly bad part. I cracked open the failed TPS & found in was in an oil bath. There is a micro switch for idle position & a points type switch for WOT. I speculate there was some sort of molecular action going on in the micro switch. When the temperature reached a threshold point… womp there it is, conductivity. I don’t claim to be a scientist, so who knows. All I know is my BMW runs great now.

Bryan

[bryan1970]

well i'm glad you figured it out becasue if i would have had something like that at work i would have been stumped after checking the basics. used