Buddie's Truck Is Acting Up...

[HDdave]

Well my friend has a 2000 1500 z71 with the 5.3. When driving at around 50 or around there at about 1500 rpm the engine's rpm's will randomly fluxuate by about 300 rpms up and down.. I havent payed enough attention to notice if it does it at any other speeds at 1500 rpms.. We tried cleaning his mass air sensor and that made no difference. His truck had sat in the shop for 7 weeks! due to a transfer case and rear end problem, and when he got it back the ses light came on 2 days after he had it. It stayed on for a couple days until he got really pissed and floored it and held it there till about 90mph and it just shut off and never came back. When it was on we had it read by autozone (they were close by) and it read a catalyst error which the guy said was probablly either a clogged cat. converter or a bad O2 sensor.. Shortly after the light went off from him flooring it (a couple days, and it started doing this with the rpms. I have no clue what the problem could be, so I'm hoping you guys could help me...

[BigJayDogg3]

This is simple. The truck is haunted. You need an exercism.

[HDdave]

Haha thats what I tried to tell him. My guess is either an air leak in the intake, or in the worst case senerio, his torque converter is bad and when it locks up in overdrive it has too much stress on it and it just locks and unlocks...

[jhm]

Sounds like valve train damage.

[HDdave]

That wouldnt be good.. What type of valve train damage could it be? Bent push rod? Does anyone else have a theory?

[Bowler807]

Just because the SES light is out does not mean the problem has been resolved. The computer is telling you there is a problem. Address the known problem and go from there.

 

Choosing to ignore the code is not a good thing to do. The fault very easily can effect the condition you are referring to.

 

It's your truck, or rather your friends. Do what you want.

[diehrd]

That sounds like the torque converter is locking and unlocking .. to test this run at a steady 50mph , depress break pedal JUST ENOUGH to turn on break lights but not enough to apply breaks .. Watch tack see if it jumps up 2 or 300 rpm (It should) ///

 

If it does is this what you are feeling when it is doing it by itself ?

[Lincoln30]

I agree that it's probably a tranny problem and the tranny problem might have caused the rear end and transfer case problem. I had a similar thing on my 99 where my tranny didn't show any symptoms I could feel but my rear gear broke. Two weeks after having a new ring and pinion put in I started having tranny problems that started with the symptoms you have described. I always suspected the tranny must have been doing something to drivetrain before I could feel it in my rear end My truck had 103K miles on it at the time. All that said, I think he should address the faults stored in the computer even if they are unrelated to these symptoms.

[AFD256]

What about the code? Did you ever check the cats?