BMW E36 M52 Motec M400 X Motronic 413

Hi guys. I recently had a customer come in with an M52 block (from what it looks like based on the manifold piping size its a 320i) running a Dbilas ITB system. The engine bay is a mess as far as the wiring goes and the car is unstable at idle and at the low range rpm band. The owner is pretty clueless as whether any of the internals have been modified. The car does not sound like its running high cams but its very unstable as previously mentioned. Attached are a couple of pictures of the engine bay.

Im assuming the white protrusion in the intake plenum is the MAP sensor.

This car is running 2 ECUs; the stock Motronic 413 ECU AND a MoTec M400 ECU. No one knows who tuned the car and installed the 2 ECUs as it has passed through many owners. This current owner is looking to keep the car for the next 10 years at least and wants long term reliability and intends to use it as a daily driver and the off track day. He wants to solve the issue of unstable idling and low rpm driving.

I advised him to work ground up and make sure his engine internals are in proper working order and condition before proceeding with any further tuning. It seems to me that this idling issue is something to do with the tune but I do not have much experience with standalone ECUs. I want to use this opportunity to fix it for him and gain some xp myself.

Would it make sense to remove the MoTec and run with the stock ECU for the time being while we focus on rebuilding his engine (Im guessing the previous tuner must have meddled with the Motronic via EEPROM so does anyone over here have any experience with that? Its been ages since my colleague has used any sort of EEPROM programmer so it would basically be starting from scratch in that aspect as well)? Once the engine is rebuilt and the wiring is neatened up I suggested we begin the switch from factory to standalone ECU.

Is this a good idea? Im looking for some advice as to whats the best way to proceed with this project.

More likely the poor running is something fundamental such as the ITB's not synced. You will be far better to stick with the M400 as it is easy to understand, openly configurable and has logging etc.

Thanks for replying Adam. By "not synced" do you mean they are mechanically out of sync with one another or does it have something to do with the throttle position sensor? Is it a problem that the its running both a MAP sensor and TPS ?

By "not synced" I mean balanced airflow. ITB's are very sensitive when near closed, a small mechanical difference will make a big difference in airflow between cylinders and they run like crap if not near perfect. I see yours has a homemade throttle linkage hence my suspicion. Easiest to check with a "synchrometer", but you can do it with a stethoscope or similar also.

Thanks for the answer Adam. Do you have any reference (like a link or video) where I can educate myself as to how this can be checked using a stethoscope?

You'd be best to buy a carb balancer to do the job. There's a bunch of different styles but here's a link to an example - https://www.ebay.com/itm/Dual-Carburetor-Synchronizer-Synchrometer-Airflow-Meter-Weber-Carb-Sync-Tool-/173869307112

I'd second Adam's suggestion - ditch the stock ECU and utilise the M400. Even given its age it's still a very capable ECU that will do everything you need and more. I'd also suggest some basic mechanical health check on the engine such as compression and leak down to get a picture of what condition the engine is in. Beyond this you need to start considering the tune and in particular the air fuel ratio and ignition timing at idle.

Alright, we haven't inspected the ECU as yet but there is a chance its locked. I guess if that's the case, then its pretty clear cut that we have to ditch that ecu because it doesn't make financial sense sending it to and fro Australia.

Do you have any experience with BMW E36s with and without the Vanos? Are you aware if a standalone ECU is capable of running this cars Air conditioning and locking system? From what we know, it is not possible, that is why I reckon the previous tuner kept the factory ECU and used the MoTec as a piggyback but I cant seem to find evidence of this anywhere on the net.