650NutKase

I've noticed a rough idle, almost like a misfire on startups, especially when cold. You know how the trucks idle high when cold for about 10 seconds, then come down to normal idle? During that raised idle, the truck sounds rough, like it's missing, or has a cam in it. Once the idle comes down, the idle is very smooth with no misses. No codes, no CEL's. Any ideas? exhaust leak? Manifolds? VCT's? hydraulic tensioners? 130k miles, all maintenance up to date. Thanks!

SCORGE

Can you replicate? Leave the truck in P but manually bring it into high-idle range?

650NutKase

I can try. I do get a tick at 900-1200 rpm when I'm cruising, so it may be the VCT's?

SCORGE

Ticks are pesky little beasts. If it's only happening at a certain range, I would maybe think the solenoids. Spark or injector tick would be constant.

650NutKase

Yeah....
One more thing to add, yesterday when I was driving, I also get a lot more exhaust noise it seems like when I really step on it. I really hope it's not the other cat going out...The passenger side did that right before it shat the bed.

SCORGE

Yeah, I'd say either a leaky manifold or clogged cat on that one. May explain why higher RPM is causing issues

650NutKase

it sounds just like this...0:18-0:19, but VERY definitive lopes. I know this is a 4.6 and I have a 5.4.

SCORGE

I think you may have a hairline manifold crack or leak. Try looking around the studs, etc. for black soot. The noise goes away after it's been running for a bit?

650NutKase

Ill check it out and report back after work!

650NutKase

It only makes that rough idle noise during the high idle when it warms up. After it comes down to normal idle, it sounds just fine. So, in other words, it makes that noise for 10 seconds after start up, regardless of weather or temp, then goes away.