CNR79

First of all, this is my first post and I thank all of you who answer. I have recently rolled 60K and decided to give my truck a thorough once over. I put on an Auto-Spring 2 1/2" level kit, new tires(stock size, Cooper Discoverer S/T's), and changed all the fluids with the appropriate Royal Purple products:

Engine oil- 5w-20 w/ K&N oil filter
Tranny- Max Atf(14 qts)
Rear Dif- 75w-140(2.5 qts)
Front Dif- 75w-90(2 qts)
Transfer Case- Max Atf(2 qts)

I also ran a bottle of Sea Foam through the vacuum line and one through the fuel tank. I also added 1/3 pt. before the oil change to the crankcase and 1/3 pt. after. The trans. fluid was flushed-no pan drop or filter change.

Now, my mpg's have been steadily decreasing and I can feel/hear the difference in the increase of engine rpm's while driving both city and hwy. My truck seems to be stiffer steering and with lag in throttle response and take off from a red light. Tach is reading 2050-2100 while cruising 80 mph on interstate. I have been racking my brain trying to figure out what could be causing this issue after replacing everything with a quality product that claims to lower rpm's and increase mpg's.

My thoughts are there is a blockage in the trans fluid coolant lines from the flush or the filter is dirty causing improper flow or all of the carbon blown from the sea foam has blocked up the catalytic converter and this is causing the engine to work harder. All gauges read normally and fluid levels are within the hash's on the dipsticks.

Can someone please help diagnose this for me and I apologize for the length of this post, just want to give as much detail as possible.

CNR79

Is it possible that the EGR valve is clogged?

Samkat93

I'm not sure if my issue is the same as your's, but I was having significant acceleration issues from 0-60. The rpm's would rev, but it just felt like the engine was choking. I replaced air and fuel filters, cleaned injectors, had full tune up done at a ford shop, and even had the catalytic converters replaced. The converters helped a little (and are covered up to 80k miles so they were free, but good luck finding them), but I still have acceleration issues. Next step is to stay on top of Ford about replacing my cam phasers which was part of the initial diagnosis. They, of course, are not covered.

CNR79

What year model is your truck and how miles did you have on it when you did all of this? Why is it hard to find catalytic converters?

Samkat93

Mine is an 04 FX4 SuperCrew. I guess I started noticing it around 65-70k miles, I think. I had to wait for about 3 months for converters. Apparently a nationwide shortage. I ended up with only one Ford-manufactured converter and the other a third party model because they just could not find another one anywhere in the country (so I'm told).

Good old Bill

This is a way off the wall. All the power loss and such, let me restart, I have experienced vehicles that just didn't get out of their own way. Engine roared and no go. Found out the fan clutch was malfunctioning making a sound level higher as is more power but actually noiser at a lesser RPM.

CNR79

It turns out the problem was my O2 sensors failed above the cat converters and it was causing it to run extremely rich resulting in terrible mpg's and overall choking down of the engine. Had it checked on a computer at my auto parts store and swapped the sensors, voila! Like driving a brand new truck. Thank you to those that responded.