My 2004 F150, 5.4L 3 valve, hesitates, then breaks up teribly at full throtlle and finally clears out above 3000 rpms and pulls fine. There are no codes being set, I have replaced the fuel filter, checked and cleanded the injectors, replaced all 4 catalytic converters, replaced all 8 coil packs. Still no improvement. Please help.

 

You might want to check the mass airflow sensor.

 

 

Yeah check the MAF. When I bought my 2005 5.4L used (it had 96000), I found that the MAF had melted. Yes, melted, so much in fact that I had to shave off plastic with a file before I could remove the sensor from the air box. Before I replaced it, my truck ran like crap unless I gave it lots of gas.
If that doesn't work for you, maybe check the fuel pump? Those things can be a pain in the *** sometimes.

 

Thanks guys, I replaced the spark plugs today. Not one broke!! Believe it or not! Problem solved. The truck runs better than the day I bought it, and I bought it NEW in 04! Thanks for your help I will check the MAF anyway, I have replaced so many things maybe it wouldn't hurt to change that as well.

 

have the same problem changed my plugs first only fixed it for like 2 weeks then went back so you may not b outta the clear yet.... where do you check the MAF sensor

 

it is in the air box, check the connector on it, also you can pull the air box out and clean the sensor with carb cleaner.

 

Be sure not to touch the wire inside the maf...if you touch that little wire element...its junk

they make MAF cleaner now!!!!!!... haha... ive never used it but ive heard they do make it... say it works well

 

yea the MAF cleaner works very well.. friend had to use it on his car! i would recommend (that is if the problem persists) to check smaller, cheaper things (fuel filter) rather than digging into pain in the a** projects like the fuel pump.

 

+1 on the MAF Cleaner.