What would be causing this?

blackout51

Original poster
Member
Oct 18, 2012
157
So lately my truck has been having a more buzzing type of vibration on top of the bad motor mount vibration, and when I shift to reverse and push the pedal the rpms drop to 450-500 then come back up before it moves, also when driving at night my lights inside and out dim when I let off the pedal for a second then return to normal brightness, not really a major problem I just am not sure what the cause is
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
When was your last throttle body cleaning?
 

blackout51

Original poster
Member
Oct 18, 2012
157
the roadie said:
I was going to guess erratic idle RPM control, usually caused by a dirty throttle body. If not that, what's your mileage, and age of plugs? Vacuum leak?

Mileage is 137,xxx plugs are a few months old and are acdelco plugs, I've checked all over and can't find a vacuum leak unless its in the gasket but I figured it'd be acting up more and giving me lean codes if I had a vacuum leak
 

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