DieselDude92

Hi all,

I'm new to the forums, but I have to say all the information here has been incredibly helpful, so thank you all.

Anyways, I have a 2007 F150 5.4 Triton with 160,000 miles that I have been chasing a lack of power and misfire at idle problem for months now, with not a single diagnostic trouble code.

Here's what's been done:
New fuel filter.
New air filter.
Cleaned MAF sensor.
Changed all spark plugs.
Replaced both timing chains, guides, and tensioners, one tensioner had collapsed and one guide was broke.
Compression check, all good.
Checked for blow by, none present.
Installs cam phaser lockouts and reprogrammed PCM with programmer from Livernoise motorsports.
Disconnected cats suspecting clogged cat, no difference.
Checked fuel pressure, good pressure under all operating conditions.

The problem still exists. Even though the rattle noise from the cam phasers and loose timing chain has been fixed, the engine STILL runs rough and misfires, to the point where it's sucks a sheet of paper back against the exhaust pipe, but ONLY at idle! It's not a dead misfire either, but it is enough to make you wonder what's wrong with the engine when you're sitting in the cab. No stalling problems, just an annoying vibration. As soon as the engine speed increases over 1000 RPM, it runs perfect. However, take it out for a drive and punch the accelerator, it has no power past 3000 RPM and starts knocking and pinging like crazy.

What gives? It has slowly gotten worse over time, and I thought for sure the collapsed tensioner and the cam phasers were causing the problem. But even after locking the phasers and installing new guides, chains, and tensioners, the problem still exists.

Also, when the engine reaches higher RPM, it's starts sounding harsh and sharp, but not to the extent of a failed rod bearing. I'm literally pulling my hair out over this, does anyone have any ideas?

Thanks!

Summers22

iTrader: (2)

Did you replace the boots and springs with that plug change? Clean the throttle body lately? Could be the cam-shaft position sensor. You also should visually check your FPDM on the axle.

Mdgonzo101

^^ Agree with the above said statement ^^

DieselDude92

I didn't replace the boots or springs when I changed the plugs, but I did apply dielectric grease to the springs and plugs, as well as clean and inspect the boots. The throttle body has been cleaned, and the cam sensors are functioning properly.


I did check the FPDM like you said, and I'm glad you mentioned that. It had a hole in it and the module was corroded. So I replaced the FPDM but still had the exact same problem.


Turns out it was a clogged catalytic converter. The funny thing is that was the first thing I checked, but I didn't check them correctly. I disconnected them and drove the vehicle, but due to the loose timing chain it still ran poorly. So I assumed the cats were good and the timing was to blame. Well, I fixed the timing problem and even though the rattle noise from the phasers and chains was gone, it still lacked power and misfired. So I tested the cats correctly this time using an exhaust backpressure gauge and HOLY CRAP, the driver side cat was stopped up solid. Removed the oxygen sensor and bingo, the truck runs like a top. Ordered a new cat, should be here in a few days.


Also, here's a video of the exhaust backpressure if anyone is interested:


Thanks for the help!