2007 GMC Sierra 5.3 problems

[Bobbie Guidry]

2007.5 Gmc Sierra 5.3

 

Recently when driving, when letting off the pedal my rpm's drop dramatically. From 1400-2000 to 500 then spike back up too higher rpm's. Ive also noticed that acceleration is very boggy. Another crazy thing it's doing is when Im barely pressing the throttle to maintain speed the afm kicks in. When it kicks into v4 mode its like the truck instantly slows down like Im hitting the breaks then spikes back when returning into v8. The truck started these problems a month ago.

 

What could be going wrong with it?

[swathdiver]

3 hours ago, Bobbie Guidry said:

2007.5 Gmc Sierra 5.3

 

Recently when driving, when letting off the pedal my rpm's drop dramatically. From 1400-2000 to 500 then spike back up too higher rpm's. Ive also noticed that acceleration is very boggy. Another crazy thing it's doing is when Im barely pressing the throttle to maintain speed the afm kicks in. When it kicks into v4 mode its like the truck instantly slows down like Im hitting the breaks then spikes back when returning into v8. The truck started these problems a month ago.

 

What could be going wrong with it?

I would replace the VLOM before it takes out the lifters.  You may have a vacuum leak or problem with TPS/MAF/MAP sensors, those would best be checked by a bi-directional scan tool.  Check your motor mounts too, especially the driver's side.  When the hydraulic mount leaks, it causes AFM engagement to feel funky.

[Mikebtte]

As said, check the TPS (throttle position sensor) they can be an issue on this truck but are easily repaired.