tcford2010

MY 300 6 HAS 178000 MILES AND HAS RAN STRONG UNTIL 2 WKS AGO WHEN IT STARTED TO IDLE ROUGH. IT RUNS GREAT AS LONG AS YOU'RE MOVING BUT IN GEAR OR AT IDLE IT KINDA HAS A LOPE TO IT. I HAVE CHECKED THE COMPUTER NO CODES. I DID A TUNE UP, CHECKED THE VACCUUM LINES, AND EGR VALVE.

NOW I'M STUMPED PLEASE HELP.

Thudpucker

IF your motor lopes, the Computer is searching and adjusting. It's in the open loop mode.
You have something going bad.
First thing I'd suspect is the O2 sensor.
THe first thing I'd change is the Plugs.

That can also be a partially plugged exhaust. Bent, or even had some gas that had a little of the wrong stuff in it and plugged the Cat.

__________________
97/F-150/4.2L/XLT/Canopy. Old boats and motors too. I like the old Fords but I gotta have the features now that I'm old.

motorhead_83

Hi,
I have been having that problem with my hi miles 300 as well. Mine is a '90 model, which will be the same for this purpose. On the right hand side of the intake, the side w/ the throttle linkage on it, there is a smaller cylindrical part right on top of where the air intake from the air cleaner goes in. This is the idel/low speed air valve, and on mine this valve keeps getting clogged up with gunky oil from blow-by, causing it to run rough, lope and sometimes stall when it is just sitting idling. Runs normal otherwise. I took mine off, cleaned it, and it runs fine now. I know that this is common on these engines with high miles.
Good Luck
Dan