Re: 502 MPI idle speed
 

just some added insight, i remember now that the last two clicks of the morse throttle control does not change the rpms, so i don't think it's a cable. I would like to try the idle screw adjustment, i will just move a little, and put back if no change is noticed.

Re: 502 MPI idle speed
 

This is good stuff to know, but i wanted to be able to exhaust my chances of fixing it in house before taking it to a shop

Re: 502 MPI idle speed
 

I can understand that. However, you really have no chance of fixing the problem by adjusting the throttle plate stop screws. You are treating a symptom, not the problem. I would recommend trying it if I thought on any level that it would help.

Not trying to bum you out, but you will need a scan tool to properly diagnose and repair this problem.

Dave

Re: 502 MPI idle speed
 

Well, i found something else out from the previous owner. I did know that the engine was modified, but to what extent i did not know. He told me that the pistons have been replaced with i believe to be JE pistons? It apparently has a different cam and crane roller rockers, so apparently has a full roller valve train now. He also told me that the rev limiter was increased to 5300 and that it had a Tyler Crocket program now?? He does not know if he has any of the paperwork for the engine rebuild, got destroyed during a divorse. So it may be hard for me to get any further details. But he is telling me that i should leave the idle alone. Not sure what to do at this point...........

Re: 502 MPI idle speed
 

You may be in luck. Tyler is a member here and can probably tell you exactly what was done to it and whether he turns the idle up. It may have to have a higher idle to prevent water reversion with the different cam.
You could either PM him through the board or go to:

http://www.crockettmarineengines.com/contact.html

Re: 502 MPI idle speed
 

problem is, i don't know who did the actual engine work, i think just the computer was sent to him. Hopefully the previous owner can shine some light on it, but it doesn't look good.

Re: 502 MPI idle speed
 

I thought we were talking about a stock engine, but my posts above still apply. Did I mention needing a scan tool? :rolleyes:

Dave

Re: 502 MPI idle speed
 

so are you saying that with the above mentioned upgrades, 600 would still be the appropriate rpm??

Re: 502 MPI idle speed
 

It is not very likely that someone has changed the idle. Still, the way to find out is to follow Dave´s proposed actions; throttle cable, IAC, vacuum leaks. If it still idles too high it may be the throttleplates or TPS out of adjustment or that someone has in fact programmed it to idle at 750-800.

Re: 502 MPI idle speed
 

If it has a cam with more tendency for reversion then a higher idle speed would be called for to prevent it from pulling water into the cylinders at idle. Tyler may have done that when he reprogrammed it.