I am in the middle of a multi-thousand mile trip out of state and had the air conditioning fail last week (fixed), now, while in the mountains, while accelerating or trying to keep speed up hills/mountains the engine just does not seem to "have it" anymore, slight hesitation, but no outright misfires or dropping load. I make this trip a couple times a year, so I know the abilities of the truck, and something is definitely not quite right. When I get home I am going to try to fix this. It still has all the original sensors in the fuel system, original injectors, coil, etc. I had to replace the throttle body about a year ago, so that's not it.

Any ideas? I have not cleaned the MAF sensor, I heard that was not really possible in the newer trucks. Was also maybe going to try seafoam.

I am taking another (longer) trip in October, and dont want to deal with it running like this, it really sucks ***** in the mountains right now. And again, I know the 4.2's limitations, I have had it for 8 years and made this same trip a dozen or more times. No CEL, no codes. Idles fine.

 

Fan clutch, fuel filter, air filter, crappy gas...Hard to say without personally looking at the truck.

 

Cats starting to clog - if that's the case do NOT seafoam it, that will just finish plugging them up.

If anything, put Techron in the gas, try that now - and fill it with high octane.

How many miles on it? If the gas filter has more than 30k on it, change it. If more than 80k, you need plugs.

The maf sensor is easily cleanable, no different than the older trucks.

 

fuel filter, fan clutch changed about a yr ago, 196k miles

had many tanks of gas thru it, threw a bottle of techron thru it a few days ago to no avail

 

The MAF takes about 5 minutes to clean. Look in the index of the Articles and How Tos for a thread with pics.

 

Take it to a muffler shop, they can test the cats for blockage.

How many miles on the plugs? Are they Motorcraft?

 

Even though only 1 year on the fuel filter, I would replace again.

In my experience, high mileage vehicles can have crud in the bottom of the tank. Letting the tank nearly run dry sucks the crud into the filter. If there has been a recent occasion where you ran the tank very low, that would point in the direction of a clogged fuel filter.

Clogged cats & bad spark plugs were mentioned by glc, certainly check those.

Another possibility on a high mileage motor is loss of compression. Before I started throwing money at sensors, injectors, coils etc... I'd check the compression to rule out a burned valve or worn rings.

 

DO NOT run Techron through a dirty fuel filter! Tried it on my truck and now have a leaky injector.

 

70k-80k or so on the plugs, yes they are motorcraft, replaced the plugs and wires about 2-3 years ago

 

I was thinking about replacing the injectors, I did it on my 2002 Lariat 4.6 and it seemed to help some, I also had one fail, so I figured I would do them all.

 

70 to 80k on the plugs, it's time for new ones.

I'd still get the cats tested.