Just replaced both phasers, tensioners (1 was ceased shut and put all sorts of slack in the passenger side timing chain), tensioner arms, guides, the water pump, timing chain sprocket, timing chains ... on my 2004 5.4L 4wd Lariat with 188k. Now that's it's all put back together I'm noticing some hesitation when putting the engine under load (accelerating without dropping gear), and a lot of fluctuation in idle speed. When coming to a stop it will drop as low as 250 rpm. At idle, it will go from about 700 rpm to 500 rpm. The biggest thing I'm noticing is the engine is dying if you remove the air filter. This makes me believe it could be the throttle body, MAF, or something else back there. Thoughts? Fuel filter? Yes, it's throwing a code but for some weird reason the truck won't talk to the code readers at Autozone/Advance/O'Reily's ... it only likes Ford computers so I have no idea what the codes are.

Please help me if you can. Thanks.

 

look for a vacuum leak or a bad seal/crack on the intake if the Maf is good.

 

The air filter helps smooth the air flow over the MAF and helps provide a uniform signal. If you remove the filter then the air becomes erratic and "dirty" ups the MAF signal making the computer change fuel trims accordingly.

So put the filter back in and a good hand held OBD2 can pull the codes(SCT X2, X3, etc, etc)

 

Check your cigar /cigarette lighter fuse. If it's blown the "cheaper" code readers will not communicate.because they do not have an internal battery.

 

My reason for asking about the air filter being removed is b/c my dad's '07 5.4 clearly runs less smoothly when it's removed but it doesn't die. Mine dies about 5 seconds after it's removed. Was just wondering if that was symptomatic of something.

As for the cigarette lighter fuse, I've had no issues charging anything from that outlet so I'm not sure. Also, the OBDII scanners will power up, they just don't link up.

I've read somewhere that weak batteries can cause problems. I haven't had a chance to check but could that be the source of my problems as well?

 

Update: I think a lot of the problem was the computer relearning the truck, ince the truck sat in pieces for over a week without the battery. It's running a lot better but still not perfectly. Now, removing the air filter only causes the engine to run less smoothly instead of stalling it out. And the idle speed has calmed down but still fluctuates. There's still a bit of a sputter during WOT so I'm leaning toward replacing the fuel module on the back axle as it appears to losing fuel under load. We'll see what we get. Still open to any other suggestions you may have.

Oh yeah, had the battery checked and it appears to have plenty of power and I just replaced the alternator about 6 months ago so I'm ruling that one out.

 

I had this occur on a customers vehicle, (back when I was still a tech) I wrote a short post on here about some of the issues with the cam phasers as well. It was a plugged fuel filter. I was working on a Hybrid Escape with an engineer from ford over a trans issue and he took a quick look at it by pulling the filter out he decided I should look at the fuel pressure which showed fine. But when under load it was losing power and cutting out like it had a timing issue. I pulled the fuel filter off and couldnt even blow through it. changed it, cleared codes and test drove, to verify it was good to go home.

 

Solid thought. I just took the filter off and blew through it with hardly any resistance. Put it back on and took the truck for a pretty rough spin. Let it get warm then started putting it through the courses: hard stops, hard acceleration, accelerate while in same gear. Noticed fewer hesitations but they were still there. I was thinking it's getting better then pulled into the driveway and the damn thing stalled. Already ordered the fuel control module for the back end so it should be at the dealership tomorrow. Will throw that on and see what I get. If it's not the solution I'll give it to my dad as I'm sure he'll need it for his '07

Thanks for the suggestion and let me know if you have any other ideas.