Hi guys, can you help?

Can anyone help?

I programmed P28 Mugen program for a P28 ECU.

The car fired up fine, no CEL and idle nicely at about 1000RPM, rev passed 4000RPM without problem,

left the car idling, then all of a sudden the RPM dipped and the CEL came on and idling went up to about 2000RPM and would not rev pass 4000RPM.

I tried this with a Skunk and Spoon program, same thing happened.

Anyone happen to know what this is? I can reset this by disconnecting the battery, but the process is repeated.

Thanks in advance.

 

there is a little chip to the upper left of the 28 pin chip, about 1/2 in. away it should be something like 74hcn343 (something like that), try replacing that. it is a logic chip, what that means is that it may be stuck in either latched or unlatched postition. which cause the car not to go over 4k rpm. which also means that when you disconnect your battery cable it cuts the power off to the ecu. which resets that chip.

 

Most likely it's not the 74HC373 or it would do it all the time. There is something deeper happening here, it might be a sensor problem, but it sounds like the ECU works fine.

 

sounds like a sensor problem to me.
what CEL is poping up?

not reving over 4k means you're in safe/limp home mode from the CEL.
since it does it with all three proms it's probibly not that. (unless they were programmed wrong)

BTW, the 74C373 is simply a register flip/flop used to set address lines to the PROM, if that was bad it would pop the CEL immediatly or possably not run at all.

 

Ok guys, it's kinda of Strange, when I reset the the ECU, the car fires up fine, no check light, and it revs freely. then all of a sudden the revs dipped, and it then goes into a Limp home mode.

I swapped the Logic chips and it does the same thing.

 

whats the check light

 

What specific P28 are you using? Post the exact serial written on the label (P28-XXX). We've come across similar problems with certain P28s, the car runs fine for a few miles then just quits (goes into limp mode).