I have a 98 F150 5.4 and have recently lost a lot of power. The truck recently hit 200,000 miles and I know it is time for new plugs and other items, but was wondering if the plugs would cause what I am seeing. The truck seems to take of with power but right before it shifts to second I can feel it start to lose power. The check engine light is not on nor has it come on since I replaced the coil and plug in cylinder 2. The truck sounds fine and will rev up in park or neutral, but driving in gear the truck just has no kick. For example I was on the highway doing 55-60, and put the pedal all the way to the floor (not kidding) and it just sat at 60 mph like it was all it had. Any and all suggestions would be appreciated, along with any 200,000 mile maintenence I should do. Thanks

 

Sounds like clogged cats to me. I'd start with the fuel filter if it has been awhile. Then I'd have the cats checked.

 

With that mileage, I would have to say a clogged cat as well. It definitely wouldn't hurt to replace your cats with 2 high flows. I would also think that new plugs would get you some gains back. How long have the current plugs been in there?

Then cleaning the TB would definitely do it a great deal of justice. Along with all of the other no brainer maint.

 

Hey jetthat. How do you check the cats to find out if they're clogged?? Also, a dirty fuel filter could cause the loss of power too??

 

You go to a muffler shop and they drill a hole on each side ot the cat and inject air and measure the flow. A dirty fuel filter could be not allowing enough fuel to power the engine. Its the first cheap regular maintenance thing..(along with the air filter)

 

On my 98 4.6 i have a rubber tube coming out of the firewall and it plugs in to the back of the throttle body. Anybody know what this is for?

 

I think that goes to the heater core. Its a water/coolant line.

 

Well, I have been driving with the loss of power due to a lack of time to work on the truck. I finally decided I was going to try the "15 min" fuel filter change last night. Well I bought the $8 tool from autozone and went to work. After 3 minutes I had the in line disconnected and was very encouraged. After 2 hours I was unable to disconnect the out line. I broke two of the $8 tools and now am having a shop remove the filter for me due to my lack of time. Needless to say I was quite upset that I could not get the filter off. Should I have taken the out-line off first or what? I don't have any idea why it wouldn't come off, but now my fuel filter looks like it took a beating.

 

Some people have troubles with them, so, don't feel bad. I have found that spraying a little penetrating oil in there and working the filter around a bit helps. Also, I make sure to use the biggest diameter tool that the fitting will take. It may just have been the quality of the tool you bought...

 

Well,
after replacing the fuel filter, fuel pump, and catalytic converters, I still have no POWER! I haven't changed the plugs yet, but I will be doing that this weekend. I am really frustrated right now, because the shop I took it to "diagnosed" the problem first as a fuel pump, but that didn't fix it. Then they said you have clogged cats, so I bought Magnaflow high flows and had them installed. It didn't change anything but the sound, I have no acceleration getting on the expressway or trying to pass someone. It's like im driving a 4 cylinder getting 12 miles to the gallon. This weekend I will be making time to try and fix this problem. I will start by changing the plugs, but do you think I should order new coils and wait to change both? Any and all suggestions are welcomed.

 

Well, as a general rule, you only want to do a job once. So, if you are going to take off the COP's when changing the plugs, and, plan on replacing them soon, you may as well wait for them to arrive. No need in doing the job twice.

AS FOR THE FUEL PUMP!@#$!!!!!

A pump is good or bad. I am willing to bet, your pump didn't get changed at all.

You were not dealing with a NO FUEL, you are dealing either with a lack of PSI (clogged filter) lack of output, (cats blocking the way) or a fire issue (plugs and coils not functioning to spec).

With your mileage, that seemed like a cat issue...

After reviewing your original post, you may have diagnosed it in your second and third sentance. Plugs and wires/coils are always the first choices to replace when getting your engine to run spec. Just for jollies, how many miles are actually on your plugs? Coils?

 

My guess would be between 80k to 100k on them, but I was not the previous owner when they were changed. I normally would have changed them first, but I have a serious lack of time due to school and work, and the shop having my truck for a week! I will order the coils from global today, and wait to change both at the same time. Is there any chance its an airflow issue?

 

What kind of shop diagnoses a fuel pump as a cause and doesn't do a pressure check?

Heck, did they even do a compression check?

It is a 200,000 mile engine you know...

You need fuel, spark and compression for an engine to run properly.

I agree with the above post that you replaced that filter, pump, and converters for nothing.

Hopefully it is plugs and coils, but the lack of diagnostic know-how is appalling.

 

I am not a big fan of this shop anyway, but the owner is a friend of the family and I was in a pinch with the filter, but I was told that my fuel system was running at 26 psi? I dont know the units off hand, and it was supposed to be around 32. Yeah, I know I got screwed there! but what can I do now? With the cats they supposedly hooked the exhaust up to a pressure gauge? not sure what or how but again I supposedly had restrictions? Well after about $700 and my truck still running terrible, I am in the same boat as last week, only just about out of funds to remedy any new problems

 

Well after 6-1/2 hours I changed the coils and plugs finally, but it did not help my throttle response/hesitation issue. I've searched and searched and just can't seem to figure this problem out. Here is a list of what I have done so far.
New fuel filter
New fuel pump
New air filter
New catalytic converters
New coils and plugs

I appreciate any help that I have received and would love to hear anything else that someone may have. My next step is to clean the TB and MAF, but again time is very hard to come by for me right now.
Here is my best description of what is happening, please give advice on what to do next.
The truck will start to accelerate from a stop, then just as it gets to second gear it is like it just dumps all power and acceleration. I can slowly put my foot to the floor and it will just continue on accelerating very slowly. The biggest problem is it doesn't do the same exact thing every time. Sometimes it will accelerate fine, other times its like has no acceleration at all. If the gas is pressed hard the RPM's will jump and the truck feels like its building up before it finally takes off. I know this is not the clearest explanation, but I am really frustrated here and just want my 5.4 to act like a 5.4. Any and all help is really appreciated.