A buddy has a '02 502 mpi engine that just went "full rich" Runs so fat,fouls plugs instantly.Will the efi temp sensor cause this? Thanks BOB

Yes I would replace the water temp sensor.

Thanks,Tyler. BOB

The ECT sensor may be the cause, but you want to check for trouble codes before you start replacing things. You can check with just a paperclip and 12 volt LED. Also, just FYI, the last production year for the 502MPI was 2000.

Dave

Sounds like its in enrichment mode. Usually the temp sender.

Make sure the map sensor is plugged in or not damaged. This will show up at idle.

Thanks guys,checked the map.I have a spare efi sensor,easy enough to change.I go from there.
Dave,don't know? It's a powerQuest('01 not a '02 like I thought)definately is a 502 mpi ??? BOB

Merc made both the 502 Mag and 496 in 2001, they rolled one out while they closed down the 502.

Well,renewing the temp sensor didn't fix it? Got no codes and the fuel is fresh.Unpluged the map and the sensor and the scan tool picked up on that so it is working.Thanks for your help.I'll fill y'all in when I figure it out. BOB

Did you check the fuel pressure?? You may have a regulator problem.