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2001 Ford Ranger Question: I have a p0171&0301. Why does my truck run ok after it warms and then sits?

 

Question

ttwotimes, 4.0L V6, Fort Collins, CO, April 22, 2013, 18:03
 Rookie

When my truck warms up I can shut it off and let it sit for about 15-25 minutes; then it will start, idle and run fine for about 2 minutes and then it will start misfiring again. Why does this happen? Also I can take my gas cap off without any check engine light coming on.

I think it could be the evap system because it seems like the fuel vapors build up or something allowing the fuel/air ratio to be higher at startup. I'm not quite sure but maybe the evap canister vent solenoid is bad without throwing a code.

Can someone please help me out with this? Thanks.

Work already performed:
-plugs and wires
-coil pack
-evap purge valve
-EGR valve and sensor
-IAC valve
-cleaned throttle body
-cleaned MAF
-fuel pump/filter
-PCM relay
-fuel pump relay
-PCV valve and fixed hose
-oxygen sensor, bank 1 upstream

1 Answer
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  • Answer #1

    pushrod April 22, 2013, 18:19
    Profile_thumbnail
     Master

    Is it Flex Fuel? Had some flex fuel sensor problems, same symptoms! Check intake manifold for vacuum leaks!!! Warm up intake seal, cool down intake leak.

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    ttwotimes, April 23, 2013, 11:42
     Rookie

    No flex, just gas. Do gaskets swell when hot and then with engine off under no pressure it would seal the leak? It has no leak or misfire for a little bit after restart.

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