Fluctuating RPMs under load

[drburke]

So it's been happening for a while but never bothered me until after I swapped gears. From idle (like at a light), as soon as the engine has a load, my rpms drop a good 1000 or more, then goes back up and continues like normal. Also, if I power brake to try and get my tires loose or lock the rear end, it just sits and fluctuates 500 rpms and the tires can't break. All the maintenance factors have been checked ie throttle body cleaned, spark plugs replaced, air filter, etc etc. I should mention it ONLY happens when the engine has been running for a little while (1 hr+) and is warm, otherwise it doesn't do it. I was thinking a sticking IAC but I figured other opinions couldn't hurt.

Case in point at WOT

[hayes]

Have you checked the trans fluid? When the oil heats up, it could be thinning out and causing low fluid levels. Also, the torque converter my be locking and unlocking.

[The Roadie]

I can't think of anything at the moment, except we have no separate IAC as some other vehicles do.

[Trail X]

Is the video of you in Park at WOT? or is it with your foot on the brake and throttle in Drive?

Do you have access to a PCM scanner or scangauge? I'd be interested to watch some of the various outputs and see which ones shouldn't be fluctuating but are... such as your TPS. I'm guessing your PCM is demanding the TPS to fluctuate like that, but I don't know the exact reason it would be doing that.

You say that you also have a loss of power when it does it?

Why is your vehicle so loud?

Have you checked the trans fluid? When the oil heats up, it could be thinning out and causing low fluid levels. Also, the torque converter my be locking and unlocking.

Torque converter doesn't lock in 1st or 2nd gears. Or at least it shouldn't.

[drburke]

In the video, foot on the throttle and brake at the same time to [try and] break the tires loose, throttle at continuous WOT; I'm not playing with it at all.. I'll check out my scanguage when I get a chance next.
Yes, there is a massive loss of power when it happens, especially when you push the throttle at a light. You can physically hear and see the truck stop accelerating then reaccelerate. Exhaust cutout, but my phone case heavily distorts all loud sounds.

[TBYODA]

Why is your vehicle so loud?

Sound like he got a ricer muffler.

[Cable810]

He straight piped it!

[Bacnbit]

I am sure you checked for vacuum leaks. Also agree with scanning and watching values. I say scanning and watching based on not seeing a check engine light on. Sounds like a vacuum leak issue and PCM trying hard to compensate. Check that line close on the drivers side by the evap test port. The I6 also has an interesting pcv system make sure all lines are on and secure. TBI is clean, And no raw fuel in fuel pressure regulator line. Just a few Ideas. And seriously What the H makes it sound like that....

[Trail X]

If you're hitting 2k rpms in drive and the truck isn't lurching violently, my first thought is that your transmission is toast. No matter the power being output by the engine, if its hitting 2k rpm, it should lurch.

What happens if you slowly let pressure off of the brakes while doing that?

Also, this is a pretty harsh test on your trans. Do you do this a lot? Could have something to do with why its broken.

[drburke]

This all started before and after the second transmission rebuild. Can't recall if it happened on the stock, though. If I slowly let off the brakes, the power comes back and all is fine. No I don't, I did it to prove the point. It's been doing this for about a year now, just never cared until recently. I'll monitor the conditions more closely tomorrow, 3 hr drive and it'll definitely happen.

Sound like he got a ricer muffler.

And seriously What the H makes it sound like that....

This lol.

[Bacnbit]

This all started before and after the second transmission rebuild. Can't recall if it happened on the stock, though. If I slowly let off the brakes, the power comes back and all is fine. No I don't, I did it to prove the point. It's been doing this for about a year now, just never cared until recently. I'll monitor the conditions more closely tomorrow, 3 hr drive and it'll definitely happen.

Sound like he got a ricer muffler.

And seriously What the H makes it sound like that....

This lol.

Oh man I could so go so many places with that picture.
But can we get captain's choice exhaust for our trucks someplace. LOL

[c0a8l0v6i8n9]

Failing torque converter?