Blown auto ECU help!
 

Some history...'93 automatic FD, 110K on the odometer. I just rebuilt my FD's engine due to a blown apex seal. I fixed a boost leak and after a couple of full throttle runs, it broke. So after rebuilding the engine, I dropped it back in on Sunday and the engine kept flooding. I figured it was because the engine had not broken itself in yet so I made every attempt to get it started. Finally it ran, after smoking a bit, but even after reaching operating temps and running a while it would still flood and not start.

Then yesterday, I came home from work and tried to start the car. It started on its own and held idle. Then out of nowhere, after jumpering the TEN pin, the engine started running smooth and basically ran like it did before the seal blew. I was relieved and left the car alone till this afternoon.

It started flooding again. The ECU was also setting the CEL, even yesterday when it ran fine. I tried numerous times to check the code, but all it would do is turn the light off for 3 seconds and then it would come back on solid without showing any codes. So I troubleshot the ground & power wiring to the ECU as well as the 1I ECU pin (the diagnostic TEN pin), which had continuity. Just for S&Gs, I took the cover off the ECU and discovered a burnt surface-mount component and blackened resistor, that conveinently enough went to the 1I pin of the ECU. I'm thinking someone down the line had connected the TEN pin to a voltage source instead of a ground. :( The bummer is, I know there's more damage to the ECU cause the CEL shuts off for 3 seconds when the TEN pin is jumpered, and just stays on when the wire is removed, so the circuit is still functioning somehow. Also yesterday, the car started to run fine after I tried jumpering the pin to see if the idle would change or the CEL would blink. So I'm assuming my ECU is done considering the car runs normal and like crap within minutes.

So my question is, a friend has a spare FD ECU, but its for a manual. Can I use this ECU to get the car running and driving around?

I do think you need the auto ECU. They shouldn't be hard or expensive to come across - post up a wanted ad and you'll probably find one before the day is over.

Take your time with it and do it right.

Dale

pm'd you about ecu

PM'd you back Adam...

I hear what you're saying Dale, I'm just paranoid about the wiring. Even if I can't drive the car around, I'd love to hear the thing idle smooth just to know that it was only the ECU. The way things are going, I wouldn't be surprised if the wiring harness has an intermittent short along with the ECU being damaged. :(

You can imagine the frustration, this is my first REW rebuild, and the second time I've touched a FD's rats nest. Before that it was a nice simple S5 in my old FC with an E6K...no surprises there. I can't wait to get a standalone on this car, I hate stock Mazda wiring & ECUs.

I have an auto ecu working great. Asking 30US+shipping if you are interested. it is an N3A2
send me a pm.

Should be pretty simple to test if that one input wire is a problem - get out your meter, and check for continuity to ground or 12v. If it's totally open circuit (which, from what you're saying, it should be) you should be OK.

I know you're dying to hear your car running good again, but one thing I stress when people do a rebuild or motor swap is *patience*. Take your time, do it right, and you won't have to do it over again.

Dale

The wire goes to the TEN pin on the diagnostic connector so its usually left alone. I'm more concerned with damage done to a brittle engine harness just by removing it to rebuild the engine. :)

I understand the patience bit, but my issue is my daily driver is also down, and I'm sharing my girlfriend's car with her. I'm a consultant so sometimes I can't make it by 5 to pick her up and that can cause problems. My daily driver is a '99 Prelude SH and has a blown clutch, which is $450 for an ACT street clutch and over 10 hours of labor due to the ATTS module my model has. :( So the RX is my best choice right now until I can get the Prelude done in a couple weeks.