Hey. My truck is smooth in Park and Neutral, but in reverse or drive the RPM's drop to about 600 and there is a vibration that can be felt. Is 600 too low in gear? as I accelerate the vibration goes away and it's smooth again. Should I be looking at the maf? iac?

I've also been trying to find the RPM specs but can't find it anywhere.

Anyone know what the RPMs should be in park/n or in gear for a 4.2L v6 automatic?

Thanks!
Corey.

 

My 2003 4.2 automatic has always idled right at 650 rpms since new. If you are feeling some vibration, you might be a little low on the 600 rpms.

Never having a vibration problem on mine, all I can suggest is the IAC, sparkplugs, wires, etc. I would be looking at the IAC first since your idle is a bit low.

 

To be honest, I don't know what my idle is in gear, I let the idle drop below 1000 before I put it into gear, I do this on every start up. 600 does seem a little low, but remember its computor controlled and is NOT ADJUSTABLE. You can adjust base idle 400-500 with IAC disconnected but that it.

 

It's a new motor with maybe 3,000 miles on it. The plugs and wires and coil pack are all brand new. IAC was used from the old motor though. Do I just clean it, or is it something that should just be replaced?

Thanks so far guys