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

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
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
No car image 94a1663db56199c5353592009e34aaa51078a2469bed068bb8d6f0ba43accf97
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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.
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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