2005 F-150 running rough

Asked by Guru5P5Q9 Jan 29, 2018 at 03:03 AM about the 2005 Ford F-150 XLT SuperCab 4WD

Question type: Maintenance & Repair

Ok first off my ‘05 F-150 has been
converted to propane as well as gas.
About 2 months ago we began having
problems with the truck running or even
starting. We started with the fuel filter and
that worked for a while but remember my
truck switches to propane automatically
after running for about 10 mins or so
depending on how cold it is. Then we
changed the fuel pump, Fuel Pump Drive
Modulator, then after having to do all that
the battery wore down and had to buy a
new on of those also. We changed the oil
thinking maybe there was something
possibly in the filter, that has seemed to
work but the truck still runs really rough
after being running for a while. She starts
with no probs any more but when you drive
it for a while you have to slowly remove
your foot off the accelerator so it won’t die
on you. What’s the deal with this thing. I’ve
had propane on the truck for 4 years and
it’s just now started doing this.

4 Answers

58,955

On the v-6 for sure and maybe the v-8 too, has two small elbow vacuum lines under the upper intake that fall apart in the 90 degree section. One is center underside front and the other off-drivers rear (fire-wall side) under-side of intake. Buy replacements at Ford dealership parts department as they are the only sellers of it as it has two different size ends on it that are not plug and play with universal vacuum lines or vacuum line fittings atleast that will fit in such small places and is also very hard to get too, the rear one is twice as hard. Make sure the PCV valve is fully seated. Your throttle body may need cleaned if so clean the IAC too and use new gaskets.

58,955

The IAC meters air flow to the engine while throttle is closed during idle or start up or when you foot is not on the gas pedal. Start there. Test it or clean it first before replacing it. And clean the throttle body too while at it. New gaskets are a must when doing this job.

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