7.4 MPI, MEFI 3 odd timing problem
10-10-2021, 01:16 AM
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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 ?
10-10-2021, 04:14 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.
10-11-2021, 09:51 AM
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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.
10-14-2021, 12:00 AM
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10-14-2021, 06:56 AM
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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
10-14-2021, 09:10 AM
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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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