Car ran fine. Started it up and now won't idle. Sounds like it's running on three cylinders.. Then idle goes up to 1500rpm. Runs fine. Idle returns to normal.. Runs like crap again. Can ROMs randomly go bad? Laptop doesn't "see" ecu any more in ecuflash.

Any ideas?

 

ROMs don't go bad.

At this point, I think we need some more detail on exactly what "running like crap" means... but to take a shot in the dark:


(1) If it both drives and idles like crap, you might want to start by checking for boost leaks.

(2) If it drives perfectly, but the RPMs ramps up and down at idle, you might want to check your base idle set screw; make sure it hasn't fallen out. Other culprits for bad idle can be the idle control valve.

 

What have you changed in the rom and did this occur after a flash? I would say start there...........

 

What these two said.

Other than that... is your MAF Plugged in? Is there a post tb boost leak? air leak anywhere (BOV return etc etc)?

 

Flash a stock base map on your car and if its still running like crap then its def. not the ECU. I've been told that if you flash the EVO ECU too much it could "lock you out" I thinks BS (I've never found anything about here).

I had similar issues and my TPS was bad. Down load the Scantech tool (OBD II code reader for PC) and see what the sensor output is.

 

The non-volatile memory in the ecu has a limited number of writes before chances for errors go up significantly (I think it is somewhere in the area of 100 according to specifications). To write the memory you must clear the whole block and then write what you want changed to 1's. Eventually the memory will not take the write and/or the clear and will be "stuck". That said, no one has really reported this problem so far and if the check that happens after the write is OK then you have not had a failed write.

 

Most commercially available flash products are guaranteed to withstand around 100,000 write-erase-cycles (though it depends somewhat on the type of flash & file system algorithms) ... I'm pretty sure that's sufficient to cover even the most avid ECU flasher (i.e. you could flash your ECU 30 times a day, every single day, for 10 years).