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7.4 MPI, MEFI 3 odd timing problem

Old 10-10-2021, 02:16 AM
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Default 7.4 MPI, MEFI 3 odd timing problem

On my 7.4 454 MPI with MEFI 3 , I hooked up a Fox Marine gateway and discovered an odd timing issue. At WOT above 3000 rpm, I seem to read only 17 degrees of timing advance. The total timing should be 32-34 degrees, so if I subtract the base timing of 8 degrees I should be reading 24 degrees advance through the ECM, not 17. I have no codes, no warnings etc. While monitoring the timing as I am accelerating, I never see it above 17 degrees, and it is not detecting any knock. I am going to recheck the base timing but I suspect it is ok, so I am not sure where to go next. The engine seems to start and run fine, although I am down about 3-5 mph from ideal top speed. Any suggestions on next steps ?
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Old 10-10-2021, 05:14 PM
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Idk why your only showing 17 but base timing of 8 degrees only make your tables correct. Ie, if you set base to 8 w a tool, the ecu commands 28, you should have 28. If you set ypur base to 10, it commands 28, w a gun you'd see 30. If ypu set ot to 6, it commands 28, it shoukd show 26 with a gun.
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Old 10-10-2021, 10:36 PM
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The problem is that the ECU is only commanding 17. The ECU is stock, not been reflashed.
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Old 10-11-2021, 08:38 AM
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Need to see if is throwing a code 44.
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Old 10-11-2021, 10:51 AM
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Originally Posted by dogturd21 View Post
The problem is that the ECU is only commanding 17. The ECU is stock, not been reflashed.
i inderstand that, i dont have answer as to why your timings stuck at only 17 but as far as "base timing at 8 degrees", it only makes the comnanded timing correct , it doesn't add or subtract from it.
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Old 10-14-2021, 01:00 AM
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Originally Posted by AllDodge View Post
Need to see if is throwing a code 44.
So far I have not seen any engine codes, but I will check again. Does this match your understanding of MEFI code 44 ?
" code 44 - cannot detect knock activity " .
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Old 10-14-2021, 07:56 AM
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Originally Posted by dogturd21 View Post
So far I have not seen any engine codes, but I will check again. Does this match your understanding of MEFI code 44 ?
" code 44 - cannot detect knock activity " .
Correct, the MEFi 3 tries to test the knock sensor on first throttle up after re-start. It advances the timing fully to make it knock. If it doesn't see it, it retards timing a bit. This can happen from using 93 octane instead of 87 gas. Mine was doing that running 89, so I went in a turned it off using MEFIBurn
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Old 10-14-2021, 10:10 AM
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Originally Posted by AllDodge View Post
Correct, the MEFi 3 tries to test the knock sensor on first throttle up after re-start. It advances the timing fully to make it knock. If it doesn't see it, it retards timing a bit. This can happen from using 93 octane instead of 87 gas. Mine was doing that running 89, so I went in a turned it off using MEFIBurn
What setting on a mefi3 does THAT? I thought it was only mefi1's with knock module, thanks, smitty
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Old 10-14-2021, 10:37 AM
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Originally Posted by articfriends View Post
What setting on a mefi3 does THAT? I thought it was only mefi1's with knock module, thanks, smitty
I don't see a 1 doing that only the 2 and 3






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Old 10-14-2021, 11:44 AM
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MEFI 1 had that problem early on, and Mercury fixed it shortly there after.
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