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OMC Cobra surging at 2000rpm

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Voyager Mark

New member
First some history on this four winds:Ford 351 5.8l MPFI
Boat losing power at top end and acceleration, cause was pick-up tube screen blocked.
Test on water w/ shop tank ok, boat tank no changed out H2O seperator and found/cleaned pickup screen. Test ran on water working fine.
Boat comes back ran all day fishing but ideling back to dock at 2000rpm motor would surge and die, start back up ok but surge and die at 2000rpm, higher or idel OK. Fuel line preasure dropping under 20.
Found crud in vapor seprerator, vent valve on top vapor seperator clogged close. cleaned complete fuel system,replaced vent value and seat, checked/cleaned injectors but looked ok. Now the motor does not die and the fuel rail preasure stays in spec but the motor still surges at 2000 rpm (rail preasure goes up and down a few lbs. Found carbon build up in IAC cleaned and replaced screen and gaskets, still surges at 2000rpm but when I disconect the TP senson the surge goes away. A dead spot in the TP senson may cause the problem and I will check that next.
Anyone have a similar problem?
Voyager Mark
 
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Just checked the TP sensor, no dead spot, will check incoming voltages and test the map sensor. Still no inputs from all you experts??????????????
Voyager Mark
Just checked voltage to TP and MAP senson has no voltage, will check output from ECM
 
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Well my test setup was bad and I do have voltage (5v)to TP sensor and the voltage change seams constant and in spec. TP sensor is OK
Map sensor voltage is 5 volts and output is 2.5 volts but no change in voltage with rpm change. Disconnect map sensor vacuum hose and hook up mini vac to map sensor, no voltage change when vacuum is applied. Check vacuum wile motor is running and vacuum is as expected. Must be a bad map sensor, better be at $265 for a new map sensor.
Thanks for all the help?
 
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