ETA to Non-ETA Swap

[Downeaster1]

Greetings all, and thank you in advance for putting up with my noobish questions.

I recently bought an 1986 325e off of Craigslist as a project. I did the timing belt, water pump, some ignition components, etc this past weekend to bring it up to speed.

When I picked up the car and drove it home, it liked to idle at around 1500-2000 rpm constantly with little to no fluctuation. When doing the timing belt, I noticed a VIN sticker under the intake manifold. I ran the VIN, and it came from a 1989 production 525i M20. Seems to me the engine may be swapped.

The chassis is a 01/1986 and the engine is a 06/1989. Being new to E30's, I'm not entirely sure with the Motronic version and how compatible the engine is in the chassis. It (to me) looks as though the DME, air meter, and everything else is specific to the eta engine, and appears to be original to the chassis.

The engine runs strong and accelerates without any issues. The only issue I'm having is that it idles very high. Any insight would be much appreciated.

[packratbimmer]

Let us know what the tachometer revs to and the number on the ECU. Is there a small module, square in shape, to the left of the ECU?

[Kershaw]

Check/replace the cold temp sensor.

[Downeaster1]

Let us know what the tachometer revs to and the number on the ECU. Is there a small module, square in shape, to the left of the ECU?

It revs to abou 5k rpm, and yes, there is a small black module. It's tucked up into the ceiling of the glovebox. Is this the idle module that everyone is talking about? I haven't removed it yet, but I'll check that tomorrow morning (I've read that it is black with a red face?).

Check/replace the cold temp sensor.

Just ordered all the temp sensors. Will be here first thing in the morning also.
I should note that embarrassingly enough, I'm a Level 1 BMW Technician and have access to Progman/GT1 if need be, but these cars are before my time as I learned everything practically on the M54 and up.

BMW's repair and diagnostic test plans listed in ISTA are sparse at best, and don't give much insight. This forum is much more thorough.

[packratbimmer]

Yes, the little black box is the idle module

[jeffnhiscars]

[QUOTE=Kershaw;4689675]Check/replace the cold temp sensor.[/QUOTE

Probably a good idea to do a leak test after figuring out just what engine and components he has before replacing anything.

[Downeaster1]

Yes, the little black box is the idle module

That's a bingo.
Swapped in a brand new one, all is good with the world. Thank you to everyone for the help.

[jeffnhiscars]

Good call. Never had an idle module that I know of.

I'll be quiet now :)

[Downeaster1]

Good call. Never had an idle module that I know of.

I'll be quiet now :)

haha no I appreciate the insight man!

[packratbimmer]

The idle modules are only on the M10 318i and the 325e/528e AFAIK. The newer dated ones are usually green. Did yours have a date on it? Just curious.

[Downeaster1]

The idle modules are only on the M10 318i and the 325e/528e AFAIK. The newer dated ones are usually green. Did yours have a date on it? Just curious.

It did. May 1st, 1985.

[packratbimmer]

I think the modules were actually a recall item that far back.

[Steve Corbett]

When I picked up my 84 325E it had a hellacious idle surge, 700-2000. I was able to get the car for half the asking price. Swapped in a different idle control module and fixed it in 5 minutes. Definitely a easy quick fix on the Eta's