Tahoe misfiring/running rough no codes

[Aaron1201]

Hey all,

2017 tahoe premier with 90k on it. Has been running like a dream until about a month ago. I started noticing the idle was a little rough, not to the point of stalling but you could feel it. Then i started noticing when driving it was almost like it was misfiring under load/heavy acceleration. Pluged my code reader up to it and found a knock sensor performance code, did a little more research and replaced the sensor, thinking that would fix it. No change, and no other codes.

Friend that works at a dealer plugged his computer up to it and told me they didnt see anything out of the ordinary with it, and just told me it was probably something related to the fuel system and recommended a injecter cleaning service for $300+ .

Just wanted to gauge some ideas on diagnosis before anything else.

 

[e3gordon]

^similar scenario - watching thread thanks

 

[Brewder]

Original spark plugs? If so, I think replacing them might be a good first step.

 

[rick1024]

watching

 

[Aaron1201]

Original spark plugs? If so, I think replacing them might be a good first step.

Figured I’d update the thread-

I removed the intake manifold and found the ports to have a lot of buildup, not as bad as others ive seen but pretty bad. I walnut blasted all the ports, new plugs, and cleaned the intake manifold as there was a lot of oily buildup in there as well. It runs significantly better but still feels like its missing slightly under load and idle, not as noticable. I’ll try and post some before and after pics of the ports

 

[ReaperHWK]

Get a catch can now so you keep it clean. These DI engine need it.

Here is what mine looked like before I cleaned it. Bought it used and it had 100k miles with no catch can.

 

[Aaron1201]

Get a catch can now so you keep it clean. These DI engine need it.

Installed one when we got it @60k miles, suprised it had that much buildup even with a catch can

 

[rick1024]

i know there are different types of catch can, like the ones that you put the pcv line into and from the catch can goes back into the intake tract, and then theres the ones where you have to remove the pcv valve and replace it with some sort of housing and then it feeds into the catch can (my golf gti had this sort of thing). which catch can do yall recommend?

 

[NYBRD]

I just ran a cheap Amazon catch can , plugged my intake ports that were going to my valve covers , breathers installed on valve covers and called it a day

 

[Aaron1201]

Just wanted to provide an update for yall-

Took it to a highly rated local shop to get a second opinion, and after 5 mins they were able to solve the issue. So the tires on the rear are worn down a little more than the front, and when the trucks in auto 4wd, its causing the fronts to speed up to match the rear, which was causing that “jerking” feeling like a misfire. Tech told me he thought it was a misfire too until he really drove it and hooked it up to their scanner. When put it 2wd its as smooth as can be. Honestly I never would’ve though that was the issue.