Consistent problem at higher speeds under hard acceleration, in 2nd or 3rd gear(auto trans): My tach tops out at about 4750 rpm, past that it drops way low swings wildly up and down, engine rpms seem to stay at upper range not sagging with tach, but definely don't go higher. Am I experiencing an ECU based rev limit? Saw mention of a rotor based rev limiter in my forum search but have no clue about that. Could it be a combo of ECU rev limit and funky tach/cable? Are the tachs generally accurate? If it's all working properly, does anyone have experience futzing with changing the rev limit resistor in the ECU? Thinking I'd buy a spare ECU for monkeying with.
You see there's this mountain road with limited passing space and I need to feel more secure and not have the engine give up when I need it most.
TIA and Happy 2016!
1981 528i auto trans, California car
Rev Limits
Rev Limits
1981 Sapphire blue automatic
Hit 200k mi. on Fathers Day 2016!
250k October 2020
Family owned since new
Route 150 between Ojai and Santa Barbara
Hit 200k mi. on Fathers Day 2016!
250k October 2020
Family owned since new
Route 150 between Ojai and Santa Barbara
- John in Simi Valley
- Site Admin
- Posts: 274
- Joined: Thu Dec 20, 2007 10:24 pm
- Location: Formally Simi Valley, Ca.
Ignition Control Module
You are describing symptoms of a defective Ignition Control Module.
It's the small aluminum electronic box located in the engine compartment on the right side. Two screws fasten it in front of the right wheel well.
BMW P/N 12141267459
Rmfd control unit transistoriz.ignition
My parts bin is fresh out of these, otherwise I'd mail you one for testing.
Early BMWs from 1975 through 1983 (I think) had these, so 3,5,6 & 7 series L-Jet ignition used them. It's part of the distributor ignition circuit.
It's the small aluminum electronic box located in the engine compartment on the right side. Two screws fasten it in front of the right wheel well.
BMW P/N 12141267459
Rmfd control unit transistoriz.ignition
My parts bin is fresh out of these, otherwise I'd mail you one for testing.
Early BMWs from 1975 through 1983 (I think) had these, so 3,5,6 & 7 series L-Jet ignition used them. It's part of the distributor ignition circuit.
John Savage
1980 528i 5-Speed
FirstFives COTM Editor
1980 528i 5-Speed
FirstFives COTM Editor
There is a built in rev limiter in the ECU, it limits fuel over 6400-6600 range, clearly not what you're getting if your tach is anywhere near correct. I did recently have a problem where the tach was way off, almost double, and at higher revs would bounce up and down, but the car ran fine and didn't cut out.
The module John referenced was used on E12 528is and 633/733s thru 81, but not 3 series or 3.0 engines. I think I have a couple if that seems to be the problem. In the recent past I've seen them for sale at not bad at all prices and just stupid expensive prices. The latter seems to be the current pricing.
The module John referenced was used on E12 528is and 633/733s thru 81, but not 3 series or 3.0 engines. I think I have a couple if that seems to be the problem. In the recent past I've seen them for sale at not bad at all prices and just stupid expensive prices. The latter seems to be the current pricing.
Mike W.
1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
They do, but the price is still just slightly less incredible.RonDwyer wrote:The price on them on Real OEM is incredible. I wonder if Programa rebuilds them?
Mike W.
1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
Re: Rev Limits
Programa still repairs these as of today for $95 plus shipping. The rebuilt OEM units are being sold by them for $655. Yikes. Mine evidently died but had a spare (hat tip Lock). I'm going to repair my original while I still can. Used ones on eBay are north of $100.
(oo=00=oo) Eric
1981 528i Manual
1981 528i Manual
Re: Rev Limits
What's the failure rate on these ICM's? Should I get a spare for our race car?
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