Where to begin...

[Squiddy1987]

I'm not sure if I should be putting this in a different area or if this one's okay. Let's start off I've got a 2004 GMC Yukon 5.3 flex fuel love my truck don't get me wrong but she has been a major pain in my f****** ass! The truck runs fine only if my ABS light is on and my brake light is on if those lights are off when I start the truck and I start driving I'll randomly have power searches as I'm trying to drive. To give a little more description is I'll be driving going normal speed and all of a sudden I'll lose power for just a second and then it comes back and it'll keep doing this until those two lights come on. I don't know what has caused this issue I never really had any issues of this truck until I had to do the motor mounts I never knew how bad my motor mounts were until I went to make a turn and my idler arm caught the transmission line. I've tried going through checking all my grounds to figure out any other issues that it could possibly be and I am all out I've had our transmission replaced twice first time after we first got the truck second time I had left in the morning for work and we always had a really hard shift but I was told by the transmission guys it would work itself out well it never did and I was told that it was okay. As I do understand this is my first Yukon and I was Dumb and listened to the transmission guys now a year down the road or two after my warranty had expired I pulled out of my apartment complex and heard a really loud boom then the truck wouldn't go anywhere according to the next guy I had working on the transmission it had grenaded itself destroying the whole back end. Now my transmission is doing fine shifts smooth like butter but I have that issue with those two lights the truck will run beautifully if those two lights are on if they are not I have the power surge issue. Has anyone else ever had this issue thank you again for any input hope you guys have a great day!!

 

[Squiddy1987]

Still has this issue...

 

[Fless]

Have the drivetrain and chassis/body codes read and post them up so we have a little more context.

 

[afpj]

Addition to codes, check those front hubs

 

[B-train]

It sounds like you have ABS or traction control kicking on falsely. This will/can feel like a power surge due to the fact that it reduces power to the engine during this activation. The fact that its fine WHEN the lights are on means the system is in default, base brakes mode - no electrical overrides present.

Most likely an input such as a wheel speed sensor flaking out. Check the fronts as @afpj mentioned, they were prone to rust failures

 

[swathdiver]

I can't read that anymore. If it was broken up into paragraphs...

 

[Fless]

I can't read that anymore. If it was broken up into paragraphs...

The "enter" key is probably broken...

 

[Squiddy1987]

My apologies for the non-paragraphs I was at a point that I just was Fed Up. I will most certainly work on my punctuation next time LOL!

I'll go through and check the front hubs on my next day off which is probably going to be next weekend.

 

[Fless]

If you can put your hands on a scanner that will see all four wheel speed sensors, and possibly graph them, it may show a problem.

Getting the chassis codes could point to that without any physical work other than reading a scanner.