campbecl

As the subject above says, I have a 04 Lariat with 105K miles. I have noticed over the last 5K miles or so that the truck 'groans' a bit under light acceleration. Not sure why it does it...all speeds, all gears but sporadic. If I put it in neutral and rev the engine, I don't notice it at all. Engine hot or cold...it does it. When I punch it it stops the groan and doesn't seem as loud. It's intermittent at best. I'm not sure what it is. Recent work includes:
- new plugs and COPs
- induction service/cleaned Throttle Body
- cleaned MAF
- visual inspection of exhaust shows no leaks

Transmission shifts smoothly. No CEL or codes ever. Can't figure if the cats are clogged or what. I'm a long time lurked and first time poster and figured I'd check with you all. All suggestions welcome. Thx!

campbecl

Still having similar issues. No codes, no nothing. Anyone have any thoughts?

screw04

Its just the air passing through the muffler at certain rpms, mines always done it, mainly in high gear under light acceleration

campbecl

Thats what I thought too but it's almost a power zap. Exhaust sounds really loud, significant power loss too. If I punch it, the throttle responds and it pulls out of this 'mode' and purrs just fine. If I don't punch it and let it struggle through, eventually it does by the time the transmission shifts again. Really weird. Normally between 2 and 3 gear. Never throws a code, check engine light or flashing wrench. No stored codes. I'm stumped.

screw04

Thats different then mine, mine only does it in high gear under light acceleration from around 50-55mph

Northern Woodworker

Hey campbecl, did you ever find out what was making that groaning noise?