CP3

2011 Crew Cab FX4 - 5.0L V8 with 110k miles.

Never had any real issues with motor up until recently, and I've owned the truck since it had 0 miles. I've noticed my truck has become a little more sluggish lately, and has developed a weird moan. The best way to describe it is an oscillating moan/bog that's most noticeable when cruising at highway speeds. It seems like it's an exact pattern of ~3 seconds running normal, then a ~3 second moan/small "bog" that almost sounds like I'm running over the rumble strips on the side of the interstate (not quite as severe as that though). Doesn't really sputter or knock, just 3 seconds of what feels like a little added resistance to either the engine or drivetrain that you can feel holding the truck back. It is continuous for the entire drive and doesn't get any better/worse for the duration of the drive. Just a consistent 3 seconds of running fine, 3 seconds with moan/bog/resistance, and repeat over and over. Trying to hold a constant speed or using cruise control is what makes it the most noticeable. No CEL at this point, and scan isn't showing any codes. It also seems to hesitate a little when trying to pass someone. Like I said, no real knock or sputter, just like a pattern of a small reduction or restriction on power.

It's almost hard for me to tell if it's engine related, or something maybe on the drive train adding resistance. All I know is it is a perfect continuous pattern of normal-bog-normal-bog-normal-bog-etc...

Any one have an idea of where I should start looking?

Tothemax

Have you recently done any maintenance to it? When was the last time you fueled up? How about plugs, Air filter and cleaned the Air flow sensors? Have you tried resetting the KAM or throttle position sensor?

CP3

I cleaned the throttle body around 20,000 miles ago since it was pretty gummed up. Also cleaned the MAF sensor while I was in there. Didn't have any real issues before or after that though. Other than that, just routine oil and air filter changes over the life of the truck. I'm about due for new oil/filters but I don't really think that is the issue.

I guess I could start with changing out the plugs/coils first? (I'm still on the originals). It's just weird to me that the "moan" oscillates on and off in an almost exact timed pattern.

Tothemax

If you shift into neutral does it continue to make the noise?

CP3

Not really that I can tell, It definitely is something that seems to happen when the ungine is under a load.

I changed oil, filters and plugs and it seems to be running much better now though

0811Bud

hey did you happen to figure out what that was causing that “bogging” issue?
pretty sure I’m having the same issue as you were describing. Any info is much appreciated.

thanks.