Rough idling in Park or Neutral

**willbradfan** · 05-14-2009, 01:20 AM

I only get a rough idle when the gears are in Park or Neutral, any other gear the idle is smooth when I just have my foot on the brake. When in park my battery charge is right at the 14v charge rate, i started messing around and I pressed all of my window buttons down at the same and realized that my volt charge drops under 14 and my idle smooths out. Any ideas what could be causing this??

**heavy chevy** · 05-14-2009, 01:29 AM

could be that you need to change your plugs and wires. Just a suggestion on that.

**willbradfan** · 05-14-2009, 02:08 AM

Originally Posted by heavy chevy

could be that you need to change your plugs and wires. Just a suggestion on that.

The plugs were replaced around last december, but I don't think i have replaced the wires in 1.5-2yrs maybe? They are the platinum napa wires that have a lifetime warranty, some shop put them in when I was out of town and the driver of my suburban needed to get it fixed to drive.

**heavy chevy** · 05-14-2009, 03:37 AM

check fuel filter and make sure your air filter is clean

**willbradfan** · 05-14-2009, 08:23 AM

Just replaced fuel filter not to long ago and just cleaned the K&N filter as well. This has been bothering for me awhile and ive just been living with the rough idle for the past 6months and nothing has popped up that could direct me to the problem, tempted to just leave it alone again but if anyone has any other ideas im glad to hear them, would be nice to have a smooth idle in P or N again.

**MrShorty** · 05-14-2009, 12:23 PM

What year?

Any vacuum leaks?

**willbradfan** · 05-14-2009, 12:56 PM

Originally Posted by MrShorty

What year?

Any vacuum leaks?

It is a 1996, didn't realize my year of the suburban was the only thing missing in my sig..

I have never checked for vacuum leaks as I am not very familiar with anything related to the vacuum system on vehicles.

**MrShorty** · 05-14-2009, 03:00 PM

Locate vacuum hoses (like the one going to the brake booster) and make sure they are all connected and there are no signs of leaks/hissing.

I might put a fuel pressure gauge on it and make sure fuel delivery is up to snuff.

Any codes/pending codes in the computer? If you have a scanner, it might also be useful to look at some of the PID's while the engine's idling to see if there is anything obviously out of range.

**willbradfan** · 05-14-2009, 03:23 PM

I noticed that the vacuum line that connects to the brake booster was sort of damp where it is hose clamped onto the booster, it shouldn't be wet in any way right? The only scanner I have is a cheap $80 scanner from walmart that allows me to pull the service codes, ive been meaning to invest in an actual scanner that i can get real time data from the engine, any recommendations on the scanner. I will have to go check some other vacuum lines. any other major vacuum lines that you could easily point out? Thanks!