1999 5.4l Stumble
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1999 5.4l Stumble
i own a 1999 f150 bought it 3 months ago my fathers a licensed auto mechanic it need a transmission so me and him over hauled it. when we got it back together the engine stumble/flutters but only after the engine gets warm i work at a mechanics shop and scanned the truck all that came up was onboard monitor cycle p1000 code and a bunch of o2 sensors so i got the 2 02 sensors and still same result and the codes went away but p1000 was still there so i changed fuel filter air filter and did all the spark plugs. cleaned throttle body. i scanned the torque converter and locked up 100% so i m running out of options might just take it to ford if i cant figure it out. has after market true duals with aftermarket cats but all o2 sensor are still in it and runs fine while tested. if anyone can shed some light on this would be appreciated! brandon 1999 5.4l 2 valve regular cab short box.
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More specific info needed, stumble off idle, idling,accelerating, in overdrive, did you look at live scan running, at cops firing, injectors firing,clean maf
COPs, usually first sign of failure is a stumble when hot, and not throw codes
COPs, usually first sign of failure is a stumble when hot, and not throw codes
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engine stumbles as soon as the heat temp gauge goes up stumbles through all gears and idle just when ever gets warm. scanned it while running lots and have had a few licensed mechanic read the scanner and never found nothing unusual never had any codes with plugs injectors or coils thats why im stumped. ive try many fuel cleaners even the expensive 30 dollar little bottles nothing seemed to help
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The crankshaft and the cam shaft sensor is a possibility,which is a pain to change due to ac mounting,cam sensor is easy,both or one not reading right, weak maf voltage swing signal to pcm,egr stuck wide open would stall engine, partially stuck would cause a cold stumble as well as hot, whats the vacuum on engine idling hot? fuel pressure reading at rail?
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wouldnt a code come up for one of those sensors tho? i no maf stands for mass air flow but what does it all do. never checked vacuum or rail pressure.
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Maf measures the air flow into the intake so the pcm can adjust the timing and the fuel ratio, dirty maf sensors throw off this signal, worn mafs have an interuption in signal throwing off the pcm
Ive seen those sensors throw off the pcm as it reads these and the o2 sensors to detect problems
I would do the free checks first, like clean maf wire with maf cleaner, measure voltage swing, check vacuum and fuel pressure, unplug cops one at time idling check for difference, unplug injectors one a time see difference,
check for vacuum leaks if you have a low reading, connecting inline at the evap white hose above brake booster is my spot i found easiest to connect
Ive seen those sensors throw off the pcm as it reads these and the o2 sensors to detect problems
I would do the free checks first, like clean maf wire with maf cleaner, measure voltage swing, check vacuum and fuel pressure, unplug cops one at time idling check for difference, unplug injectors one a time see difference,
check for vacuum leaks if you have a low reading, connecting inline at the evap white hose above brake booster is my spot i found easiest to connect
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