Slow acceleration?

2008 CHEVROLET SUBURBAN
246,700 MILES • 5.3L • V8 • 4WD • AUTOMATIC
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JR47
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Have a slow acceleration. It revs high up to around 3k rpm before shifting and up hill i have to put the pedal almost all the way to floor to get it to pick up and go. For some background we did just install a afm delete kit and installed everything and followed every procedure as required but now it's doing this slow to take accelerate issue.
Dec 21, 2025 at 5:23 PM
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STRAILER
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Do you have any trouble codes? This can be a clogged catalytic converter or and weak fuel pump. Here is a guide to go over for low engine power but I would run the codes as well.

https://www.youtube.com/watch?v=U1RoG3I-Oww

and

https://www.2carpros.com/articles/engine-has-low-power-output

Also, are you sure all 8 cylinders are working? Please go over these guides and get back to us. Can you upload a video of the engine under power so I can hear it?
Dec 22, 2025 at 11:05 AM
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JR47
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Does that video need to be under load while driving?
Dec 22, 2025 at 12:56 PM
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STRAILER
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If you could that would be great, I want to know if the engine is running on 4 or 8 cylinders.
Dec 23, 2025 at 9:58 AM
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JR47
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So hooked the scanner up to it and got codes P0016 P0102 and P0449 which i do have the part to replace for that code just haven't got to it yet. It also gave me codes for the cylinder deactivation due to having to take the obd2 dongle out that disables the afm

If the new tensioner failed for some reason could I just put on a chain damper? I see alot of other people suggesting to get a ls2 style damper or should I just get another tensioner.
I did discover the old chain tensioner had broken after taking the timing cover off when I first started disassembling everything
Dec 27, 2025 at 2:39 PM
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STRAILER
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The first thing I would do is make sure you have all of the computer system grounds actacted to the engine, if you have one of it will cause this issue. Also, make sure the MAF sensor does not have any leaks between the sensor and the intake.

P0016 - Crankshaft / Camshaft Position Correlation (Bank 1 Sensor A)
P0102 - Mass Air Flow (MAF) Sensor Circuit Low
P0449 - EVAP Vent Solenoid Control Circuit

The P0016 code is the concern. It is telling us the camshaft is not in the correct position. Did you have the front of the engine apart and the timing chain off?
Dec 29, 2025 at 9:25 AM
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JR47
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The afm delete kit did require replacing the cam so yeah, could something have moved or maybe it's off a tooth? It did take some time to get the cam sprocket lined up with that little pin on the end of the camshaft. It all looked lined up but maybe it wasn't. I can take front apart again this weekend and take a look at it
Dec 29, 2025 at 9:42 AM
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STRAILER
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Yep, this will be the first move, please upload an image of the marks lined up so I can see them please.
Dec 30, 2025 at 9:22 AM
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JR47
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The cam mark is off
Image (Click to enlarge)
Attached Media
Jan 10, 2026 at 4:29 PM
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STRAILER
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Yep, good find, that is the problem :) nice work. Thanks for the image and for letting us know, we are here to help, please use 2CarPros anytime.
Jan 11, 2026 at 9:46 AM
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JR47
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So it still doing the slow accelerating ordeal where you gotta push the pedal down far for it to get going. Aligning the timing marks did take care of the P0016 code now all im left with is the P0449 code which will be taken care of this weekend. I know the obd2 dongle only disables the afm but am i going to need a tune/reprogram for the ecu to solve this issue?
Jan 16, 2026 at 3:04 PM
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STRAILER
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So you are not getting any codes that is good, but it sounds like you have a clogged catalytic converter. Here is a video to help test it.

https://www.youtube.com/watch?v=kNXh1Lphzr4

Please let us know what happens.
Jan 17, 2026 at 9:32 AM