Need A Ford Doctor...Bout to Tap-Out.

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YakBasser

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Ive got a '90 F-150, 4.9L Big Six that Ive been throwin $$$ at for a month now. Some days it runs perfectly fine and others stalls and chokes itself out. So far Ive cleaned all grounds, replaced Batt and Batt Cables, New O2 Sensor,New IAC Valve, New Throttle Position Sensor, New Plugs, Wires, and Rotor, New EGR Valve, New MAP Sensor, New Temp Sensor and New Intake Air Temp Sensor, Cleaned Throttle Body Intake Valves and ran a whole can of Berrymans thru the Intake. Will Sometimes run OK but at high idle, then eventually start stalling again. Sprayed around intake gasket checking for leaks and couldnt find anything. Replaced alot of vaccum lines. Brake Booster holds vaccum so I dont think its leaking.

A Lady at Autozone says theyve seen this many times and that its some kind of a timing control module thats not available aftermarket or from Ford anymore.

Am I gona hafta Shoot It????? Any help appreciated............
 

4play

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Did you check the throttle body gasket for a vacuum leak. Those were pretty bad about failure on the 4.9L because of the EGR. MAP sensor vac line new or good? is the vacuum port for MAP clean/clear? When it runs bad, are you getting black smoke like its rich? When it dies, does it restart?
 

4play

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You said you checked the intake gasket for leaks, but I was talking about the gasket at the throttle body. These engines also had problems with the fuel pressure regulator, they would either allow excessive pressure or allow fuel to be passed through the vac line on top of the regulator and into the intake. Do you have a way to measure fuel pressure? It should be 40-50psi, 40psi engine running and 50psi with key-on.
 

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