Bad Idle in P / N not in D / R

Brandon96 · 08-07-2010, 12:41 AM

My truck won't hold a steady idle, it seems to rapidly change from 750ish RPMs to 830-850 RPMs and lopes every 15 seconds or so. It really seems like it's trying to steady the idle but only gets a constant RPM going for 2 maybe 3 seconds at completely random intervals. It's nothing bad like it wants to stall or actually revvs, it's just annoying now that I have Flowmaster Duals

It all disappears when I put the truck in Drive or Reverse and it never lopes or idles funny when I let off the gas or sit at intersections.

My plugs/wires are good, PCV is new, I unplugged the MAF, cleaned the IAC/DPFE, no vacuum leaks but has new intake/EGR rings, Lucas' injector cleaner and SeaFoam seem to smooth out the vibrations, but still won't correct the idle.

Does anyone have any suggestions or something I can try? I'm curious as to how well an IAC valve can handle 155k miles

Brandon96 · 08-18-2010, 06:50 PM

Got an Autozone IAC valve today, didn't help the idle so I took it back and picked up some plugs because I could.

I have also noticed some serious drag and surging when the A/C is on or I've got her defrosting.

Any Ideas?

08-07-2010, 12:41 AM	#1
Brandon96 Wannabe Elite Explorer Central Virginia '96 XLT 4.0 OHV Join Date: Sep 2008 Posts: 1,325 Vehicle Specs (Original Poster)	Bad Idle in P / N not in D / R My truck won't hold a steady idle, it seems to rapidly change from 750ish RPMs to 830-850 RPMs and lopes every 15 seconds or so. It really seems like it's trying to steady the idle but only gets a constant RPM going for 2 maybe 3 seconds at completely random intervals. It's nothing bad like it wants to stall or actually revvs, it's just annoying now that I have Flowmaster Duals It all disappears when I put the truck in Drive or Reverse and it never lopes or idles funny when I let off the gas or sit at intersections. My plugs/wires are good, PCV is new, I unplugged the MAF, cleaned the IAC/DPFE, no vacuum leaks but has new intake/EGR rings, Lucas' injector cleaner and SeaFoam seem to smooth out the vibrations, but still won't correct the idle. Does anyone have any suggestions or something I can try? I'm curious as to how well an IAC valve can handle 155k miles __________________ 1996 XLT 4x4 - TruckTruck BUILT 4.0L OHV/SOHC Hybrid - Done. Before - After

08-18-2010, 06:50 PM	#2
Brandon96 Wannabe Elite Explorer Central Virginia '96 XLT 4.0 OHV Join Date: Sep 2008 Posts: 1,325 Vehicle Specs (Original Poster)	Got an Autozone IAC valve today, didn't help the idle so I took it back and picked up some plugs because I could. I have also noticed some serious drag and surging when the A/C is on or I've got her defrosting. Any Ideas? __________________ 1996 XLT 4x4 - TruckTruck BUILT 4.0L OHV/SOHC Hybrid - Done. Before - After