Awful throttle response after doing oil and fuel filters..

[H0USE]

just rolled over 93,000 miles on my 08 and did the oil change and fuel filters, using all motorcraft filters and rotella oil like I did previously. Went really slow, being very careful, cleaning surfaces, lubing the seals, etc. No leaks anywhere. Did the purging of air before starting it for the first time.

Now I took it for a test drive and it falls on its face. I can drive and keep it up to speed, but that mostly instant throttle response and boost built up is not there. It revs fine in park and neutral, just seems to not build too much boost when driving. Have not noticed any noises or codes.

The truck is all stock. It feels like it was detuned and I have a brick under the go pedal. My only thought is that I tightened all the 36mm caps too tight?

[Smoke2008]

The tighten too tight....would be odd. There has got to be another issue. I had the the HPFP go out on my truck....I drove it hard when it was acting up....it only then threw a check engine code....I would test drive somemore get it to throw a check engine code and go from there. Good luck and please keep us informed....

[H0USE]

the problem was during my first test drive,

after I waited an hour, I drove it home and it is back to normal. very strange problem, I still want to figure out what happened. Perhaps one of the turbos actuator was stuck or something.

[hodge1995]

I would say it was working air out of the lines and filters.Even purging would not likely get all the air out.

[azkcr]

My roommates 6.4l had a similar problem. There is only one turbo that has VGT and it's the smaller one.
And yes, the "actuator" can malfunction. When my rm's 6.4l was acting up, he took it to the dealer and they couldn't
find anything wrong (Imagine that)..
It eventually stopped acting up.

[harley1rocker]

bad problamo is the o-ring to the filter houseing can get pinched and suc air,you wont notice it and it wont leak,my suggestion would be take both upper and lower fuel filters off again and carfully check the o-rings...

ive had it happen to me twice now

[azkcr]

Stock 6.4s have reeeeally crappy throttle response anyways..
So if you're having more lag than usual, I bet a kid on his trike will get a jump on you.. lol