Rev Limiter on ECM or Safe Mode
 

On a MEFI3 ECM, how does the ECM determine the load and RPM to limit over reving? Does it use the throttle position and RPM?

If so, is it possible that the Dyno is putting too much or too little load on my engine at the higher RPMs and the ECM is detecting the throttle setting relative to RPM and going into safe mode?

I have exhusted every test in the manual and nothing has worked. I have traced all the discreet system wires and they all ohm out good. I have removed, tested or replaced all senders and sensors. Is it possible that the engine is fine and the method of running it up to speed and load is causing the ECM to go into safe/limp mode?

Or am I just SCREWED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!?????????? ????

I don't want to be negative here. But from what I have read on this board I thought the computer stored the over rev code?

Thats not negative, thats correct. Except my ECM goes into safe mode and when I hook up the scan tool, I don't get any codes.

I've tried this with 2 ECMs, same results.

Kirk, bring it up. If we can't fix it or determine what's wrong with it so you can fix it, I won't charge you.

Rod

Thats an offer hard to refuse considering your frustration.

Kirk, that is the best offer you are going to get, and not that far away either. Rod that is a great offer, especially when it is not a stock type setup. I am really interested in the cause of this. It just don't make sense, but then again when the problem is found, it will make sense. Good luck!

I agree, Rod is a great guy and has helped me alot already. I just don't want to overlook a simple issue before going that route.

How do most Dyno Shops run up EFI Supercharged engines? Do they run them up under load and hold RPM? Is it possible that the engine is fine but the dyno is causing the ECM to go into safe mode due to the throttle position vs load?

If anyone familiar with the recommended run up on a dyno could answer this, I may have found my problem.

Kirk, The only way to do a valid dyno test throughout the range is to run it up under load.

No, throttle position has nothing to do with the load sensed, examples from both sides. Its very easy to run a non loaded engine to its rev limiter, like in neutral and conversely, if it were load sensitive with respect to throttle position you'd never be able to get it on plane because it would have full load long before you ever got on plane.



Rod