ECU failure

[edavidson]

FYI - this may not be news to some of the veteran e30 folks, but to the others, especially those like me who are new to this series and the e30, hope this might help someone.

On Saturday my ECU failed. I didn’t know it at the time, so I spent about 2 hours going through the Bentley manual trying to diagnose/fix a bizarre idle problem - fluctuating between 500 and 2000 rpms - rapidly and constantly without relenting.

Finally found a tech post at www.pelicanparts.com that nailed the issue. I swapped the old ECU - a Motronic 1.1 ("153") with a used Motronic 1.3 (lots of parts numbers, but mine was a "173") and I’m running again with no error codes. Apparently the Motronic 1.1 is a less than desirable ECU and the 1.3 is the recommended replacement and easy to find since they used them in a lot of the x25 i cars.

Thanks to Sean Thompson for his help in diagnosing the problem.

Ed

[nasaregistrar]

rumor has that there are a bunch of 153 ECU’s that have some possible cold solder joints on the PC boards and the solder joints crack and fail. I have heard of them being resoldered and "fixing" the problem.
Also it is recommended to disconnect ANY ECU from the harness prior to welding on the car…Even a little bit

[nasaregistrar]

one other failure that will strand you is the Motronic relay…it is the white one, next to the 2 orange ones mountee under the black cover in front of the main fuse block under the hood on the drivers side. If this relay fails, no power to the ecu and the car …she no start.

[sdais]

nasaregistrar wrote:

one other failure that will strand you is the Motronic relay…it is the white one, next to the 2 orange ones mountee under the black cover in front of the main fuse block under the hood on the drivers side. If this relay fails, no power to the ecu and the car …she no start.

I imagine these would probably be good spares to throw in the toolbox - thanks for the tip. My list keeps growing…

I also hadn’t heard of the issue with some of the ECUs. I’ll have to remember that one.

[nasaregistrar]

sdais wrote:

[quote]nasaregistrar wrote:

one other failure that will strand you is the Motronic relay…it is the white one, next to the 2 orange ones mountee under the black cover in front of the main fuse block under the hood on the drivers side. If this relay fails, no power to the ecu and the car …she no start.

I imagine these would probably be good spares to throw in the toolbox - thanks for the tip. My list keeps growing…

I also hadn’t heard of the issue with some of the ECUs. I’ll have to remember that one.[/quote]
The orange ones are 02 sensor heater and fuel pump relays. They are interchangeable.