Rough Idle in Drive

acdac21 · October 26, 2020

Good morning,

I'm new here, so please forgive me if I'm not doing this correctly. I have a 2009 Silverado 1500 4x4 Z71 with 5.3 Vortec with approximately 117k miles. It's burned oil ever since I've owned it (bought it with 68k miles on it). I noticed it idling very rough over the last couple of days, but it only does it when in Drive and stopped; it runs fine when I'm actually driving it, or when it's in Park/Neutral. It has always had a slight shudder, in park/neutral, but nothing like what it's doing when in Drive and stationary. I did notice that it was a quart low on oil a couple of days ago, and I filled it to the fill line, but a quart low isn't going to cause this problem. Any ideas what might be wrong? To my knowledge, my truck has original plugs, coils, and wires. The transmission has a slight slip in 4th at lower speeds, and has since shortly I after I purchased the truck. Just trying to give as much background info as I can.

Thank you!

riverbanks · October 26, 2020

Good chance you have a fouled plug,1,4,6,7 are afm,start there and remember which one is fouled,you'll be doing it again,when?hard to say

riverbanks · October 26, 2020

SB-10062524-7690.pdf

acdac21 · October 26, 2020

28 minutes ago, riverbanks said:

Good chance you have a fouled plug,1,4,6,7 are afm,start there and remember which one is fouled,you'll be doing it again,when?hard to say

Thank you. I'll start pulling plugs and looking at them this weekend. I have the luxury of working remotely, so I shouldn't have any reason to drive my truck before having a chance to look at the plugs. Any idea as to why it only runs poorly when I put it in Drive and am sitting still?

Ian Mills · October 27, 2020

I would look at your PCV valve as a cause of the idle issue and potentially the oil burning issue. A clear symptom of a bad PCV valve is an oily film inside the intake manifold. If you take off your air intake and push the throttle valve open with your finger (with the engine off) you'll be able to determine if there is oil in your intake. If there's oil there, use a throttle body/intake cleaner such as seafoam and replace your PCV valve.