Hello all,

My 2004 F-150 4x4 Lariat was running fine and had lots of power and torque. Then last April the vacuum line in the back of the engine came off and it ran like crap for months before I could eventually figure what the problem was (Read about that problem here. ) I reconnected the line last September and it was running back to normal - or so I thought - however, since that time it has been gutless with no passing power or torque. It no longer hunts or dies at stop lights, but this thing can't hardly go up a slight grade or get out of its own way. If I'm on the highway and floor it to get going, it will downshift and rev to 4K RPM, but will actually start going slower. It's like the engine is doing all it can, but somehow is not being translated to the wheels or something in the engine is bogging down or retarding or loss of fuel. I don't know what's happening. It actually had better passing power when the vacuum line was disconnected. These trucks aren't known for great MPG, but I was around 13-14 MPG before, now it's about 11 MPG.

The only thing I have done when it was not running right last year was: Change both VVT cam phaser solenoids, a new fuel filter, and all 4 new O2 sensors.
The check engine light has come on a couple of times. The code is P0420: Catalyst System Efficiency Below Threshold Bank 1 and 2. I don't think that would cause the engine to not run as bad as it has and it certainly wouldn't degrade that bad overnight or coincidentally after I fix the vacuum leak.

Is it possible the VVT cam phasers are bad or not sending the right signals or are retarding the cams (they were just O'reily brand solenoids)? If they were bad I would assume a check engine light would come on to let me know though, right?

Anyway, I am hoping someone with better wisdom than me would have a good lead on what the problem might be. Thanks!

 

not an expert by no means, but i have heard that anything but motorcraft parts in the vct system is asking for trouble.

 

Thought I would update the results of this for future readers who may encounter the same problem.

Short answer: I had extremely clogged catalytic convertors.

On both sides the packing on the first cats completely collapsed and had actually gone down the pipe into the secondary cat. Having those removed brought a whole new life to this pickup that I forget I used to have.



There should be nothing to see inside the O2 sensor hole.

Totally empty of any cat material.

 

Maybe the vacuum leak leaned the mix, the computor adjusted for it, started dumping extra fuel in, over heated the cats.

 

I hadn't thought about that, but you might be right.

 

I'm sorry I missed this, my answer for anything that suddenly seems low on power but otherwise idles fine and has zero codes outside emissions is to check the cats.

For anyone that wants to check this, just loosen the nuts at the connector ahead of the cat. If it revs faster, you've got a clogged cat. Don't drive, really hot exhaust isn't good for electrical wires and connectors.