Also interesting, ran mefi4 on my blower motor and various other projects plus ran and tuned quite a few mefi3s now, must be in flags and schalars table, i do turn most the code crap off anything modified, will have to open up a bin file when i get back to shop and see what i can find, Smitty

[QUOTE=articfriends;4486161]Yes by the bulletin date and more specifically the serial numbers mentioned within the bulletin. Merc altered the test later to preclude this as being an issue.

[QUOTE=Trash;4486193]Ever heard of it on a mefi 3 or four?, I know on passenger car when you first start them if the KNOCK sensor is shorted out or has an open circuit with no resistance whatsoever it could throw a code but I've never heard of a mefi 3 or four testing actual knock upon start up based on octane and then deciding to go to a limp default mode?

I was a bit in error for MEFI 3 and 4, it shows up for 2, 3 and 4. Was not part of MEFI 1

So I just left the engine shop and this motor has already been rebuilt once before. Also a roller cam was added at the first rebuild. Bearings are not horrible and Pistons have light scuffing on the skirts. Probably only needs a honing and new Pistons/rings and head job. Probably only needed to replace head gaskets. I should have pulled the heads before sending it off but oh well I'll have a fresh engine again. If I knew more about having the ECM programmed and wanted to buy some good exhaust I would try to wake it up a little bit but just staying stock.

[QUOTE=articfriends;4486264]I have not. This is the only bulletin I've seen regarding this issue. I ran into it way back in 1994 when these motors first came out.

[QUOTE=Trash;4486527]I called bob at mefiburn and he told me that indeed there IS this possibility on some, not all, mefi3's and 4s, he said. The essiest way to ensure it never happens Is to un-check the flag for code44, knock sensor will still work IF it sees knock but wont do no unexpected things do to a start up table.

[QUOTE=articfriends;4488323]Thanks for passing that info on!

I looked at several tunes I have, looks like most the stuff Tyler crockett has done has #44 unchecked, a stock hp 500 does have it checked but there are other things in the tune that will affect wether it "test" knock sensor and what it does IF it doesnt see knock on intital startup, some you can see with std mefi burn, some you need mefi pro to see,seems strange that merc had a bulletin saying it was a concern on early mefi1s but not a concern later, Bob wasnt specific as to what had it and didnt have it ie maybe stock ramjet 502 does but not mercruiser fwiw, Smitty

IF I dyno my stock hp500 efis this winter I will check timing at a certain map/rpm then disconnect the knock sensor and see if total timing is reduced somewhere and post my results, will be after January probably though, Smitty