I recently bought an 04 lariat crew cab with 56K miles 5.4 and auto trans. Before i bought it i complained about an exhaust noise and acceleration issue at 40mph and 1100 rpm as well as the ac not being very cold. They replaced the exhaust manafold on the passanger side, coil pack on the #3 cylinder, a transmission flush, a flash drive update and recharged the ac. This seemed to take care of the problem but i mostly drove under 30mph and did not notice it. I took it on a few road trips, and country roads and noticed the problem of sputtering and shuttering between 40-60 mph's after decelerating and slowly accelerating. The problem occurs consistenly with ac and over-drive on in the above mentioned conditions and mph range. Problem is less noticable with ac off and have not noticed it at all with over-drive off. It feels like a limited slip kicking in or driving on dry pavement in 4wd. Tranny shifts fine through all gears in a straight pull of acceleration and even full throttle pulls. Problem only occurs after decelerating and slowly accelerating. I dont know of any codes as I dont have a code reader, but I have not had any check engine lights come on nor has the dealer mentioned any codes. Any thoughts?

 

When was the last time the spark plugs were replaced?

 

Thanks for the replie. I beleive that they are orginal. It was bought new at the dealership I bought it used from they gave me the car fax with the maintaince they did(not very detailed). The guy before me seemed to follow the maintance intervals so I would guess since they recomend 100k that they were not done. How hard are they in this truck? I know from looking at it that it is not as easy as it was in my 91! Why would I only expierence it at certain speeds and conditions and not all around performance? thx again

 

Overdrive and AC add additional load to the engine at low rpm...I changed my plugs (72000 miles) and it went away.

 

I had the same thing with a 2005. Changing ALL of the plugs fixed it. If you are going to change the plugs, GET THE PULLER TOOL FIRST. Chances are you are going to break at least half of the plugs off in the engine when you try to get them out. The puller tool that Ford made to extract them after being broken off works great although it is tedious. 2004 and 2005 5.4L engines are notorious for this issue. I got my puller tool from Ebay for about $65. I had those exact same symptoms and tried everything. The plugs were the problem.

 

Ok so I called the stealership today to find out first if they would do the work under warrany as I had the problem before it expired. After bouncing around a few managers including the one who basicaly sold me the truck. No such luck! So than I ask the service manager for an estimate to replace the spark plugs- $475! So that is not happening. I asked him for the price of the plugs and said $25 or so each! I couldnt ask him about the puller tool because my jaw was still on the floor. Is ford the only one who sells the plugs? I checked a few local parts stores and no motorcraft plugs for my truck. So am I looking at a DIY plug replacement for around a little under $300 for 8 spark plugs and a puller tool and some quality time with my truck or am I missing something?

 

I used autolite HT1 from autozone at $12 each. They worked great. Get the puller tool on eBay or amazon for $65 or so. Those HT1s are made for that engine.

 

I've heard of mixed results when using plugs other than Motorcraft. I got mine at O'Reilly's for $7.99 a plug.