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Old 09-24-2021, 12:54 PM
RDahler RDahler is offline
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Join Date: Feb 2016
Boat: Mastercraft Prostar 190 1988 351 sold, x25 2013 6.0, Protour 190 Lt1 1994
Location: Southeast
Posts: 117
I see a lot of good recommendations on here. The only for sure way to know what the ECM is seeing from the sensors and what commands it is sending to the Engine is by connecting a Diacom and looking at the data to figure out were the problem is. Here is a Diacom screen shot of my LT1 running to give you a look at what I am talking about.
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Old 09-24-2021, 01:53 PM
ValveCoverGasket's Avatar
ValveCoverGasket ValveCoverGasket is offline
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Join Date: Aug 2016
Boat: '04 X9
Location: pnw
Posts: 672
Originally Posted by 88 PS190 View Post
Several of the sensors can be well out of range and throw no codes.

Basically if your engine thinks it is 0 degrees when it is 100 degrees its going to run really rich, but since 0 degrees is a value the computer is OK with that will never throw a code.

If a value is incorrect but inside range no codes ever.
in range failures - at least in my experience - are more rare. not impossible but id say unlikely

and that still doesnt account for his large cylinder to cylinder variation.
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Old 09-26-2021, 03:13 PM
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1redTA 1redTA is offline
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Join Date: Aug 2009
Boat: 1981 MasterCraft 351W slot
Location: Pace, FL
Posts: 1,710
check the valve springs on the affected cylinders
1981 MasterCraft
19' Skier 351W PowerSlot
Long gone is the Trans AM waiting for another
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