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1996 4.9 Runs Real Rough

  #1  
Old 10-20-2018, 05:57 PM
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1996 4.9 Runs Real Rough

Bought this '96 F-150 a week ago running rough. Has the 4.9L six with 5 speed. Read computer and got a bunch of O2 sensor codes and a crankshaft position sensor code. PO had .been 'working' on the truck and the EGR valve has been removed and a plate put in it's place and the tube welded shut. Several vacuum lines are laying loose but don't feel any vacuum being pulled while running. Ordered a new distributor, A1 Cardone, with cap and rotor on ebay for $55 and put it in, runs a little better. Bumped crank around to the timing mark and set distributor at 1, had to rotate dist. a little counterclockwise to get to start easier. Changed fuel filter today, tried to take bracket off but no clearance by tank. Old filter had muddy looking dirt running out. of it, engine seemed like it was starving for fuel. Cleaned MAS, TB, IAC, and attempted to test TPS with ohm meter but hard to hold probes on contacts and move throttle, and my DMM has a few burned out spots so hard to read. After all this it runs better but still rough. Running up to higher RPM's before shifting helps and if it starts running rough easing off throttle helps. Has fairly new Autolite standard type plugs, pulled #1 and closed gap a little. The wires are new but off brand, have experienced problems on another Ford before with cheap wires. Any advice, testing techniques, etc appreciated.
 
  #2  
Old 10-20-2018, 06:44 PM
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Check throttle body gasket. Get a can of propane and while the engine is running turn on gas (don't light) and wave around everywhere there is a gasket (intake,throttle body,etc) if there is a leak it will be shown as it sucks in the propane. Borrow a DMM that works and check the TPS,

I'd also check the fuel pressure while at it and it wouldn't hurt to run some sea foam through the fuel system to clean it and injectors.
 
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Old 10-20-2018, 07:06 PM
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I've got a variable propane regulator I can hook up to a 20# cylinder and turn it on and off easily. Will have to get a loaner fuel pressure tester at parts store. Thanks for these suggestions.
 
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Old 10-27-2018, 05:31 PM
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Did the propane test today and have leakage at the air filter housing, and at the hose connection by the mass air sensor. Tried to reposition hose and tighten and removed and reinstalled air cleaner lid but both points still failed the propane test. Will try to source one of these at the salvage yard. Had it idling a while then battery seemed weak. Charged battery full charge and ran somewhat better but still has miss. It's Walmarts best battery but over 5 years old. To be continued...
 
  #5  
Old 10-27-2018, 10:06 PM
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Which codes did you get? A '96 has both upstream sensor(s) (these matter) and a downstream sensor (doesn't matter). If its a code for "sensor 1" (either bank), its the upstream sensor. Is it rich, lean, heater circuit, or something else?
 


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