Hi guys,
I have a 2011 Tahoe 5.3L, I love the car, I’ve always wanted one and bought one in March of last year. It ran great and was super reliable until April of this year. It currently has 172,000 miles on it. Here are my symptoms:
- Rough idle, like you can see the RPMs dip down from 500 to 450 sometimes even 400 momentarily, and you can feel the tremor, you can even see the engine block shake under the hood!
- Very sluggish acceleration. When accelerating from a stop, the RPMs barely rise even when pressing the pedal harder.
- Sometimes when trying to accelerate, it’s like the car doesn’t know what gear it’s in, it sputters until it falls into gear.
- Sometimes it doesn’t even respond to throttle at all.
Here’s what I’ve done so far: I’ve replaced the throttle body twice, replaced all injectors, installed a high pressure oil pump (I had a weak oil pressure issue too), replaced the fuel pump, replaced all spark plugs, replaced all coils, replaced oil filters, tried different oil, nothing. I should also add that the transmission blew at 170,000, so I had it rebuilt. I was having this problem already before the transmission went out. I’m at a loss here.

I should also add that when I have the A/C on 3 or higher speed, the tremors are unnoticeable, but the car is still very sluggish. When the A/C is off, the tremors are extremely noticeable and the RPMs start to dip up and down.

I also have an additional problem with the throttle body. I have replaced it twice with the problem that it still sticks. Every time I come to a stop, the car downshifts very hard, and it takes time for the RPMs to come back down to normal idle. Already tried a reset through a scanner. It doesn’t respond to that reset or any.

 

I just went through 2.5 mpg loss issue on mine. That's a lot when it only gets 19 hwy. normally. No codes set in the PCM. Zero codes in all 4 of the code families either.
My scan tool has a MAP sensor 1 and 2 test in it and it didn't pass one of the 2 tests but yet it did not set a P failure code. Replaced the sensor and my mileage came back normal. Only found it after digging through all the test features in my scan tool.
Without my springing for a high end scan tool a few years ago and being a tech in another field for decades being able to understand electronic control systems I never would have found the issue. Dealer / shop repair would have cost to fix for more than I paid for a good scan tool.
Full scan of all 4 code families is a must, P code scan is not enough as their can be no P codes but U , C and B codes.
Loss of power could be a plugged cat. No contact thermometer to check their temps in / out is a way to check or removing front O2 sensors and a quick test drive. There are back pressure tests also if you have the tools.
Reman. T bodies can be problematic.
On the weird stuff sometimes you have to throw in the towel and have a pro with experience and the tools and access to the factory tech. assistance center access figure it out, I would have before wasting money on unneeded expensive parts in my case.

 

Sounds like a clogged fuel filter. You can replace just the filter for cheap, or the whole fuel pump assembly for around 300