Did you ever get this figured out? I cleaned my TB about 15,000 ago and noticed something similar right away. What mine was doing is with the cruise set the RPMs would play every once in a while. I would cruise at say 1500 RPMs and out of the blue it would go up to like 1800, almost like a down shift. Almost right after it done this, maybe 5 seconds or so it would settle back down to 1500 and may be a few minutes before it would do it again. Over 1000 miles or so it got better or I just got used to it.

It is now doing what you describe. I have been noticing it for a few weeks now but it would be sporadic and only at idle right after driving. On my way home from work this morning it is doing the lurch and idle play at red lights. It seems that just after completing the stop the RPMs will jump to 800 then down to 300 then back up to 1200 then level off, and maybe jump once more over a minute. It is getting increasingly worse and very noticeable. I dont have any lights though.

 

BigDaddy, I'm still in the process of getting this fixed. Mine got worse and worse quickly and now I get the ETC light flashing at me about everyday. The only code that was coming up was a vaccum leak. I checked all the hoses etc. and everything was fine. I replaced the EGR Valve and changed all the spark plugs (I needed to do that anyway) and it would run pretty good except randomly the ETC light would flash and go into limp mode. I finally decided to take it in to a dealer. They ran all the electrical tests and checked for leaks and everything was fine. They said that the trottle body was starting to go bad. I got it scheduled tomorrow to get a new throttle body put on (which wasn't as expensive as I thought it would be). Hopefully that fixes it because I don't know what else it could be.

 

Now, this may be a WAYYYYY dumb question...... but do our trucks have a IAC sensor? My old truck used to carry on like the op is describing, and that was my fix....

Chad... As you know, the tb is one of the easiest things we can replace on our trucks... why pay someone else to do it when you already know how? Just curious, not trying to step on any toes

 

bigdaddy,

your issue sounds more like a torque converter on it's way out.. locking and unlocking..

you may want to check your tranny fluid, and possibly do the check delete mod on your tranny-to-cooler line..

 

The trans fluid level is fine. Its almost time to change it again though. What is this check valve for and how do I go about removing it?

I read about it in causing a trans failure in passing a few months back but never did find out what its actually intended for, and what the effects of removing it are.

 

I realize this and told them that at the dealership. I was just going to buy the part and do it myself. But they said they would only charge me for 15 minutes of labor so 1/4 the hourly rate. Anyway, for about $20 I felt like it was a good deal for them to do it just in case it doesn't fix it they're the ones that are responsible for it. But generally I agree, it is an easy part to change out.

 

To update my last post, I checked the fluid level when the truck was cold and it was between the holes one the "cold" level of the dipstick. Apparently this translates to 3/4 quart low when its warm. I was always taught to check trans level when engine is hot so this is the reading I went with. I added the 3/4 quart and went for a drive. All is well now. Apparently that was my problem.

A couple concerns I have here. The 1st and obvious one is where the hell is my transmission fluid going? I have a seep coming from the tailshaft seal where the driveshaft connects. It leaves no puddles and appears to only be a seap. Could the whole 3/4 quart leak through this over time and never leave a spot on the driveway?

 

+2 on the IAC sensor

 

I'll get flamed for this, but:

It's w/o fortune that most manuals, along with the dipsticks themselves won't tell you accurately what you need in that thing.. nobody can give a clear answer on how much of your fluid is being held by your TC.. and then it differs from manual to manual just 'how' to check fluid in those things..

what seems to work for me is at operating temperature.. so after at least a ten minute drive.. on level ground.. and after cycling the trans through all the gears, with about a five-ten second pause between each, and back to neutral..

as far as 3/4 a quart? who the hell could guess where that went.. you coulda pulled that much out over a 30k mile period by checking it twice a week.. or it could be holed up in the cooler.. or burned off.. or absorbed.. but if it has 'escaped' somehow, I don't think that qualifies as a leak.. it sounds more like a vent line drip after working the hell out of it, or parking on steep grade or some such..

I'm glad to hear you got a handle on it dude!

 

Hell that may be a way to tell when it gets low lol. I have 147,9xx miles on it now and its due for another fluid/filter change at 150,000. I will go ahead and change the $12 seal while I am at it though.