Hello all I'm hoping somebody can help me out, I have an 03 f-150 xlt 4.2 I changed the motor a little over a year ago it has about 50k on it, the issue I am having is when I start the truck it's revving up and down a lot but when it fully warms up it runs great but it seems like it take awhile to warm up, I changed the fuel filter, spark plugs and wires and coil pack also changed the IAC motor I clean the MAF and checked for a vac leak that seems good but I'm still have the same issue, somebody told me to unplug the power clip for the throttle position sensor then start the truck if it still happens then the sensor is good well it did happen so I guess that's good then I was told to unplug the wire clip the the IAC to see if that went bad again and if it was bad the truck would shut off but the idle just got a little lower so I guess that's good, the only codes coming up are for the 02 sensors because I took off the cats and put strait pipe the cats went bad, I'm not sure what else to do or check any help would be great thanks

 

Go back to the AIC and pull it off and clean it. You will most likely find it fairly carboned or rusted up. Do a good cleaning as best possible, then spray some good cleaner on the slide in the two holes. Reassemble. Also check the TBI unit for crud on the back of the butterfly. It most likely is clogged up a bit and may need to be removed to be cleaned fully. There are a couple small air holes that get filled and need cleaning to keep the idle up. Lastly, check the MAF and clean with a good MAF cleaner. That, should give you a good basis to get the idle back to normal.

PS...check your PCV valve for good flow.

 

I took off the throttle body off the truck and cleaned it with carb cleaner and a toothbrush I removed the IAC motor it was clean I bought it new not to long ago but I sprayed it down anyway, I bought a can of mass air flow sensor cleaner and cleaned the sensor I also sprayed carb cleaner on the vac lines it didn't rev up so I'm assuming there's no vac leak but I'm not to sure, new plugs and wires and fuel filter, this only idles up and down when it's cold. I don't have the catalytic converters on the truck they went bad so I put strait pipe I have the clips for the 02 sensors plugged in but I tie wrapped the sensors under the truck not into anything can this have anything to do with it?

 

How do I check the PCV valve for good flow? I took the little elbow off and put my finger on the elbow and valve to check for air or a vac there wasn't much there is that how I check it? Sorry

 

Pull it out and shake it, and if it doesn't rattle then replace it!

 

I did that it didn't work could it be my TPS?

 

Could be , but I'm doubting it. You can check your tps with a digital meter. If you want to know how exactly, YouTube has a good video on checking the TPS.

Have you checked for a vacuum leak since you did all the other obvious items I asked. Have you run codes to see if any are set, that can lead us to your problem?

 

Check that elbow carefully for cracks or holes. That was the cause of my surging idle.

 

I checked the codes again today and it's only coming up with the 02 sensors I bought a new TPS today just in case It was bad but I got the same thing I also unhooked the battery for about 5 hours I went out so I just left it unplugged till I got home a little while ago. I checked again for a vac leak by spraying carb cleaner on all the air lines a again nothing. What I did notice was the tube going from the bottom side of the TB going to the back top of the I think the head cover not sure it's a hose with an elbow going in has some oil all around it the other part of it is going to a part on the TB that I think sucks in air I put my finger on it and it was a vac when I took my finger off it would click so I'm assuming that's fine there's also 2 more lines on that same part I think for anti freeze any other ideas? Thanks guys

 

After changing the TPS yesterday it seems worse now the it was before