ECU Resetting?
 

Had a strange one yesterday. Car is a JDM Evo8 running 96531706. This issue has developed recently. The issue only seems to happen in 4th gear at about 6100 rpm. At this point the car bucks momentarily like when you hit fuel cut and the check engine light comes on for a few seconds. If you datalog the car when this happens the log stops at the same time that the issue happens.

I was thinking cam or crank sensor but in this case the ECU doesn't store a code for this issue even though the check light comes on. I disconnected the coolant temp sensor and it stores a code for that. This means the ECU is able to store check codes. Also I have previously had cars with cam/crank sensor issues and it doesn't cause datalogging to stop.

We changed the cam sensor anyway but it does the same thing.

I was thinking about it afterwards and the idea came to me that the only time the ECU turns on the check light without throwing a code is when it is powered up initially. So I am now thinking that the issue is that the ECU is momentarily losing power and resetting. You would expect this to be just a loose connection in the wiring harness but if that is the case why does it only happen in 4th gear above 6000rpm.

Anyone ever experience anything like this before?

I was hoping someone would have had an experience like this but it seems not.

From what I know so far I believe the issue is with the ECU itself. We are going to replace it and see. This issue has been flashed many many times (likely over 500, maybe as much as 1000) so I am wondering if that has anything to do with it.

reviving this because i am having the exact same issue. except mine has only happened like twice; both at low rpm in second gear just as i mash the throttle. Feels like fuel cut and the CEL lights up; engine dies; evoscan stops logging. After a few seconds the CEL goes away and the car restarts fine..
The ECU is also not storing the code either.
i have heard a clicking from behind the dash whilst this happens too. Sometimes it happens for a split second whilst cruising; car stutters and CEL comes on. but im guessing because its still in gear; once the CEL goes away; the car restarts itself.

im running an evo 7 ecu with tephrav7 in my evo 3.
only permanent CEL is the front generator error (normal; never had issues before).

only thing i can think of thats changed recently is i switched off the periphery bits for the EGR fault codes (P0400/P0401 etc) as it was throwing those.

(apologies for punctuation.. using the special keyboard at work which dosnt have all the keys!)

Electrical interference can cause it.

Like with a modified ignition system that's done wrong.
Or having a cellphone too close when it takes a call.

Check spark plugs.

What is happening with battery voltage at these times?

In my experience this happens for two reasons.

1. No fuel or fuel pump choking.
2. Ecu flashed with a corrupt XML.

this

non resistor plugs can cause this.