Is "MAP" a backup for "MAF" failure? ('95 LT1) - Third Generation F-Body Message Boards

dr76 · 05-22-2008, 10:23 PM

* This is for a '95 Vette LT1 using an F-Body ECM (installed in a '76 Stingray)

Been out of the tuning/logging loop for a while, but just decided to do some logging w/ DataMaster and came up with a DTC code 48 (MAF System Fail)... MIL not illuminated, so I didn't even know.

I thought that the MAP/Speed Density "took over" if there was a MAF fault, but when I disconnect the MAF the engine dies immediately. When I disconnect the MAP/Speed density (MAF still connected), the MIL illuminates and both fans come on, but engine stays running.

If the engine stays running w/ the MAP/Speed Density disconnected, is there REALLY a MAF fault?

My TunerCat file does NOT have "Speed Density Enabled" 'checked'. If it is 'checked', does that mean it's solely running on MAP/Speed Density or that MAP will "take over" if a MAF failure occured?

'95 LT1/4L60e

Thanks

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chevyracingrox · 05-24-2008, 09:44 AM

well, my general understanding is that the MAF sends the ECU the main info for how much fuel to send. The MAP (manifold absolute pressure) acts more like the choke for fuel injection. It can be complicated, and i'll have to look up more.

chevyracingrox · 05-24-2008, 10:11 AM

ok, i looked it up in my chilton's service manual. MAP measures changes in manifold pressure(thats a given). it helps determine fuel delivery. MAF this determines the amount of air entering the engine. so the ECU needs both to run at its best.