I started having this issue with my truck just prior to changing my plugs this past week. here goes. when I go to anything over 1/2 throttle and the truck hits 3000 rpm (like in passing gear) the truck cuts out almost as if it hit the rev limiter. then comes back and runs fine as long as im not over half throttle. now if I take my time and give it enough gas that it goes over 3k it will run fine all the way up to 5k rpms. The truck isnt throwing any codes either.

The other issue im having is about every 400 miles I have to add a qt of tranny fluid, I have checked all over the truck for a leak but cant find anything. could it be leaking into the transfer case and could these two issues be related?

The truck is a 2004 f150, crew cab, 4x4, 5.4L it is lifted with 35's has a airaid cold air kit and flowmaster exaust with 180k miles on it.

thanks in advance

 

Possible causes could be the COPs, dirty MAF and dirty throttle body. Do you have a custom tune? If not, you may have been running lean so long you have damaged some internals. The 2004s ran very lean from the factory and a CAI without a custom tune can do damage.

 

oh forgot to mention, I changed the fuel filter as well about 10k miles ago, get the tranny serviced and the fuel system regularly

 

thanks. Ill check the maf out and I just cleaned the throttle body the day before I changed my plugs. I was thinking the COPs but wouldnt 1 cop going bad cause just a miss and not a rev limiter or speed limiter type effect? yes I forgot to mention i do have a aftermarket tuner

 

Did you try to read codes with your tuner?

 

no codes

 

What programmer, and with what tunes? If they are generic canned tunes, that can be even worse than no tune at all.

 

um I believe it was a superchips tuner. I installed the tune, exaust and cold air when the truck was brand new and never had a issue until now (180k and 8 years later)

 

If indeed you have been running lean, it can take that long before burned valves become evident. Was that a canned tune or one written specifically for a 5.4 with your CAI?

Hopefully, that is not it, but certainly a possibility to consider.

 

it was a canned tune. nothing specific to my truck. I dont think it is a burnt valve because the truck runs smooth other then when i give it to much gas then as soon as it hit 3000 rpms it acts as if it hit a speed limiter and cuts out for a second but if I ease into it the throttle it will go over 3k and pull all the way to 5k. i was thinking a sensor or something could be going bad.

 

Have you tried returning the tune to stock?

 

I know this is an old thread, but my truck just started doing the exact same thing. It is a 2004 F150 with the 5.4 - bone stock. What did you ever find for a problem? I'm pretty sure it's electrical as it has had no decline in performance and runs great below that engine speed, and cuts when climbing a hill and it downshifts and revs above 3,000. The rpm's drop to ~2,900 and then rev back up to ~ 3,200 back and forth about twice a second as long as the cruise is on or I have my foot on the gas.

 

how many miles on the plugs?

 

Good question. I bought it used last year and it has a little over 100,000 miles, so my guess is they need changed. It doesn't ever misfire or act like it has power loss though. It goes strong right up until it cuts back electronically.

 

I would change the plugs, clean the MAF and throttle body and see what happens.