M52 swap finally up and running...got a couple questions

[Nick325is]

After much work and issue after issue I've finally gotten my m52 swap completed. After 200 miles of driving it I've got a couple questions.

Here is the setup to help with my questions.

-90 325is
-obd1 m52 with treehouse connector
-s52 head and cams
-3.5hfm
-supersprint rep headers
-413 ecu with TRM chip for above mods
-getrag 260 with clutchmasters stage 1 clutch kit and JB racing 8lb flywheel
-original e30 starter

When I start the car the starter seems to stay engaged for a millisecond after the car starts. I disconnected the fuel relay and just cranked the car to make sure that the teeth of the starter were engaging the flywheel correctly. When I just crank the car the starter does not make this noise. Also, if I just bump the starter enough to barely start the car the starter does not stick.

I've never had a lightweight flywheel before...not sure if this is a symptom of this or not. I just don't want to tear up my starter or flywheel.

Secondly, everyonce and awhile the car will just cut off while it is running. The only way to resolve this issue is to bump the ecu and then the car will start right back up with no issue.

Could my ecu be bad or is there possiblty another reason it could be doing this?

I really appreciate any help that you guys can give. This section has been a huge help in getting my swap done!

Thanks,

Nick

[hoveringuy]

You may have a bad starter. I'm not an ASME guy but the bendix is supposed to pull the shaft in when it gets accelerated by the motor.

When is the car shutting down? Is it when you are cruising or at idle? After a long decceleration ? Randomly when you hit bumps?

[Nick325is]

It will usually shut down during a decel, such as when going over railroad tracks or down a hill. A quick tap on the ecu will then turn the car back on.

[Uber E30]

Well your second problem has to be either the chip, ECU, or harness. I would start by cleaning all the connections of the ECU, harness, and chip with some rubbing alcohol and then reseat everything nice and snug. If you continue to have the same problem you need to eliminate the three one by one. Start by replacing only the ECU, then chip, and hopefully it doesnt have to go to harness =P

[hoveringuy]

I think it's the tune.... he has an 8lb flywheel! My guess is it shuts down after decelerating in gear, right after you push the clutch in.

If the ECU had a bad connection the engine would stutter or shut down randomly, not just during decel.

[Uber E30]

but smacking the ECU wouldnt have anything to do with the flywheel... thats indicative of a bad connection

[Mstngcobr761]

but smacking the ECU wouldnt have anything to do with the flywheel... thats indicative of a bad connection

+1....check grounds and connections...and everything else this guy stated above

[hoveringuy]

but smacking the ECU wouldnt have anything to do with the flywheel... thats indicative of a bad connection

But a bad ECU wouldn't do in only on decel.... it would do it randomly or going over bumps. Plus, sometimes smacking it would make the car die.

[Uber E30]

A bad ECU will do whatever it pleases TBH

[Nick325is]

Quick update:

Just went to start the car in the driveway. Cranked it a few times and nothing. Hit the ecu and then tried again at it started right up?

TRM was supposed to have burned the chip for the 8lb flywheel. Whenever it shuts off I have to hit the ecu to turn it back on.

Time to get a new ecu I suppose.
-Nick

[Wh33lhop]

I recall something about the DOHC ECUs requiring a case ground. I haven't looked into it yet, you may want to.

[Mstngcobr761]

Quick update:

Just went to start the car in the driveway. Cranked it a few times and nothing. Hit the ecu and then tried again at it started right up?

TRM was supposed to have burned the chip for the 8lb flywheel. Whenever it shuts off I have to hit the ecu to turn it back on.

Time to get a new ecu I suppose.
-Nick

sounds like you have some bad connection internally in the ecu on the board in there...try to see if you can borrow someones working ECU and try it out

[Nick325is]

I recall something about the DOHC ECUs requiring a case ground. I haven't looked into it yet, you may want to.

I was wondering this myself. I messed around with the car a bit this am and if i even remotely move the ecu at all while the car is running it causes the car to have a very very loopy idle. It will sit there and rev to 3 grand then back to 1 and back again.

Does anyone have a working 413 red label ecu I can buy?

Thanks for your help thus far.

-Nick

[etxxz]

i have the same starting problem. feels like the starter just spins freely then, when you turn off the key, it may or may not make a locking noise (maybe aligned or engaged teeth) and there it starts usually, but sometimes it also slips off the flywheel and spins freely once again. happened like 6 times last night in two trips.

i have put a rebuilt starter right when i did the swap... no problem. a couple months later it starts. i'm on a 16lb chromoly flywheel. bimmerforum guys suggest a bad starter.

[Nick325is]

I've done some research and here are a couple updates on my ecu issues.

I was driving around today and the car was running great. While driving slowly in a parking lot all of a sudden the car bucked and the CEL came on. I pushed the clutch in and the r3vs were alternating between 1.5k and 2.5k. It finally settled down to an idle of about 1200 which is def higher than normal.

I tried doing the stomp test tonight and experienced a couple interesting things. I turned the key to run and I had no CEL. After noticing this I tapped the ecu and the CEL came on, however, the stomp test did not work for me. Is the ECU entirely at fault for this?

I have a treehouse harness that has the additional wires for ABS 12V and the oil level sensor. However, there is no connection for the two wires sitting unconnected by the ecu. Do I need to have this connected?

Hopefully someone can shed some light on this as I work 70 hours a week and don't really have time to trouble shoot like I would like to.

Thanks,
Nick