2001 Ford Ranger Q&A

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

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 -
Answer 1
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. -
Comment 1
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. -