I have an '01 5.4 screw 4x4 which experiences a loss of power sometimes. This is not the high IAT temp problem because I made a cold air intake which draws in air from in front of the rad. I used the autotap scanner to verify the IAT and it is well below 140. My problem starts on warm days, if I let the truck sit running for any amount of time it appears. It is not my fan, fuel pressure is OK between 30 and 40psi and I have a new DPFE sensor. Does anybody else have this problem or does anyone know what it is. My truck has 46k miles on it but has done it since I bought it. Vacuum at idle w/ac on is 18in/hg. ECT and CHT are at 200deg. MAF cleaned with no improvement. NEED HELP. Thanks in advance for your help

 

My 2001 4.6L did it too, and it's drivin me nuts. It's like going from my "max performance" tune to stock tuning. It usually happens to me this time of year, but not like this. No CEL, and everything was cleaned about 3 months ago. Not running oxygenated fuel any longer so it can't be that either...fresh fuel filter...blah blah blah. Takes FOREVER for it to hit 3500 rpm's now. Dunno what the deal is...???

 

https://www.f150online.com/forums/sh...hreadid=135440

To boldly follow where others have gone before!

It might not be the 140 degree problem but it does sound like its a timing related problem. Try some higher octane gas and see if the problem goes away.

 

I have a 2002 4.2/5sp 4x2. 24,000k
Same thing happened to me. Like someone pulled a plug. Tuning went from nice flow to lean as hell. I Changed the plugs, oil, cleaned the IAC, no codes. Tried different octane. No change.

I'm trying to set up a dyno tune. Ford couldn't find anything. tech said maybe I got a bad tank of gas.

One thing for shure my cats are popping like hell. They always have had allot of metal expansion sounds, but lately they sound like there is a migit with a ballpean hammer in there banging away.

 

Wow, my cats are louder as well. ??? One thing I did notice when I had my truck up on the rack to try and get some more exhaust work done earlier in teh week, they revved it up to hear how loud it was...I mean really got on it for a split second, it poofed whitish colored smoke. I usually get on it pretty good and it was warm so I dunno why it blew smoke. I've never noticed anything before, but then again I have a single outlet turn-down, just before the rear axle.

 

Temp1, I did try some higher octane gas and no improvement. On my scanner, best I can tell, the pcm was pulling out timing so I disconnected the knock sensor and ran a tank of gas. It seemed better until one day It started pinging. I wonder if one of my cats gets restrictive when it gets hot and causes alot of hot gasses to stay in the cylinder causing detonation on next cycle? This would make the knock sensor tell PCM to pull timing? Just a thought.

 

Yeah I wonder about my cat's as well. It feels like an air flow problem to me when it is running at temp. I triple checked my cold air intake and recently cleaned the IAC and did a sea foam cleaning as well. I was always suspect of the cats, with the excessive pinging. I brought it in to Ford and they stated there is a service bulletin but no fix since it apparently didn't effect performance. A guy on another post stated they ping becuase they are ceramic coated inside. I suspect that they don't flow right after a certain temp becuase I have been running lean since Summer started.

 

UPDATE: Well guys, my truck never stopped running like a dog so I ignored it until yesterday. I finally got a CEL. I ran home and pulled the code and got "Diff Pres EGR input low". I went to the local parts dept. and got the updated DPFE sensor for $15...took 3 min. to install. The truck runs great now!!! This morn. when I pulled across the cross street, I left em roastin on accident. Check your DPFE sensors guys. It is a small square black box that has a 3 wire harness plugged into it from the front and two black tubes coming out of the bottom that connects to the EGR ports just above the driver's side exhaust manifold / cat. The old one is a little thicker and square and smooth on top with a "Ford Motorcraft" logo. The new ones are a little thinner, more rectangled, with a "FoMoCo" logo and have a small circular deal centered on top. Good Luck!!!

 

I've got a 2001 F150 w/5.4. Since it has gotten hotter, this thing is runing horrible. When taking off from a dead stop, it acts as if it's starving for air/fuel. I've checked to make sure the fan is running to cool and it is. Once above about 2500rpm, it acts fine. I checked the price for the DPFE Sensor and they quoted $50 for the part. If you got that for $15, where did you get it at if you don't mind my asking? I want my poor truck to run like it did when it was 55 degrees.

 

Please check my thread here in the Engines forum. Should be on the first half of this first page.

 

Should move to Alaska.. rarely gets above 65! :P