Revving up and down

[bluewar02]

Hello all I'm hoping somebody can help I have an 03 f-150 xlt 4.2 after 5 min of a cold start the engine starts revving up and down a lot after it warms up sometimes it's fine and sometimes it's not and it's getting worse, the only codes coming up are for the 02 sensors I do not have cats on my truck I do have the sensors hooked up and tie wrapped under the truck I did change a lot of parts already all new parts, fuel filter, spark plugs and wires, new coil, oil change, new IAC, new TPS, cleaned the mass air flow sensor, took off and cleaned the throttle body, cleaned the EGR valve, checked the PCV valve it does rattle, I do not see or hear a vac leak I used card cleaner and sprayed all the vac lines and nothing I checked the PCV elbow that seems fine I'm not sure what else to do please help I changed the motor about a year ago it has about 40k on it 5413

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[bluewar02]

it's like somebody is stepping on the gas and letting go

[lee reece]

Does sound like a vaccum leak but I would run bottle of heat in it to see if there's moisture in the tank? This would explain a prob like that?

2007 F150 XLT FX2 SPORT - 5.4l 3V 3.73 LIMITED SLIP EDGE/EVOLUTION PROGRAMMER

[bluewar02]

How would I do that? Thanks for your help

[Raptor05121]

Wow, talk about throwing money at a problem. You could take it to Ford and they can tell you what it is

[bluewar02]

Lol yes I know what a waste of money but some things had to be done like the coil was bad on #4 so I just changed the coil and the plugs and wires but all the other stuff was for this issue

[lee reece]

How would I do that? Thanks for your help
Go to parts store and get a bottle of heat. This will take moisture out of tank but follow directions! Easy thing to check. Make sure you run all of that tank till gone.

2007 F150 XLT FX2 SPORT - 5.4l 3V 3.73 LIMITED SLIP EDGE/EVOLUTION PROGRAMMER

[bluewar02]

Thanks lee

[lee reece]

You bet man ... Let us no what you end up with?

2007 F150 XLT FX2 SPORT - 5.4l 3V 3.73 LIMITED SLIP EDGE/EVOLUTION PROGRAMMER

[bluewar02]

I did that it didn't work, it's still doing the same thing but now to add to it what it's also doing is even when it's warmed up the idle drops a lot for a sec like its gonna die then revs back up to the line below 1, and sometimes I do hear a click or grinding noise from the engine it's not a ticking sound like the engine is going bad the sound doesn't happen all the time I'm sitting in the truck now at work it's fully warmed up and the motor also shakes and I can hear the motor rev hear and there but the RPM on the dash doesn't move the only time it moves is when it's cold out and revs up and down when I have my foot on the gas it seems fine

[lee reece]

Yup should check gas pressure , sounds like maybe injector problem? 2007 F150 XLT FX2 SPORT - 5.4l 3V 3.73 LIMITED SLIP EDGE/EVOLUTION PROGRAMMER
Also recheck plug wires to make sure there's no loose conn.