1991 Ford F-150

Engine Performance problem
1991 Ford F150 6 cyl Four Wheel Drive Manual unknow miles

My truck is idling rough and hesatating on acceleration. Problem began suddenly not getting worse over time just started like somone flipped a switch. I have replaced the TPS, the EGR position sensor, new set of plugs, wires and cap and rotor. Also I replaced the MAP sensor. I made a gasket to plug the egr to verify it wasnt leaking by. I have checked for vaccume leaks and leaks in the intake manifold. I bought an obd code reader and the only code was for a non responsive purge canister selinoid I checked it and it was indeed stuck open causing a vaccume leak. Fixed that problem and that did help the idle quite a bit. So there is no check engine light, and I suppose worth mentioning its a real pain to start. It is way worse when its cold but when its hot it still dosnt start easily. Thats about all the info I have so let me know what you think. And thank you in advance.
August 28, 2009.

Check ECT(engine coolant temp) sensor, and fuel pressure regulator, test as shown in this video:

Aug 28, 2009.
Ok I checked all that, just bought a coolant temp sensor, and fuel pressure was around 56 lbs, spec says between 50-60. I hooked up a timing light today and unhooked the spout connector, couldnt even see the timing mark on #1 cyl, hooked thye light to number 2 and could see the mark then, any idea what would cause that? Im lost.


Nov 2, 2009.
IGNITION TIMING Gasoline Engines Initial Timing (TFI-IV) 1. Place transmission in Park or Neutral. Ensure A/C and heater are off. Connect inductive timing light and tachometer to engine. With engine off, disconnect the single-wire in-line spout (Yellow/Light Green wire near distributor) connector or remove shorting bar from the double- wire spout connector. Start and warm engine to normal operating temperature. 2. With engine at idle speed, check/adjust initial timing to 10 degrees BTDC. Turn engine off and reconnect the single-wire in-line spout connector or reinstall shorting bar on double-wire spout connector. Start engine and check timing advance to verify distributor is advancing beyond initial setting. Remove test equipment and reconnect all disconnected components. NOTE: Ignition timing on 2.3L with DIS and 4.0L with EDIS is not adjustable. You didnt say what engine you have, but if the timing is adjustable, try that first. If unable to, do a compression test to see if timing chain jumped a tooth. Also check for restricted exhuast, broken converter, or crushed pipes.

Nov 3, 2009.