Steve "OkieBadBoy" Osborn
Director, United Road Rally

I have a 2000 F350 7.3PSD with the 6-speed tranny. Until recently, it hasn't been 'cold' here in Oklahoma, so I haven't come across this problem. While on a recent trip up into the northeast thru WY and UT, we were in some SERIOUS cold weather...below zero a time or two. Anyway, while starting the truck in the morning, it fired right up and idled along at about 700-800 rpm...which is about normal. I then went back into the 5th wheel RV which we were pulling to pack things away, only for about 10 mins.... When I came back, I noticed the truck was idling much higher (around 12-1300), and there was a "hissing" noise from the exhaust...which sounded like there was a constriction in the pipe, or the turbo was trying to wind up. When I put my foot on the clutch, it immediately dropped back down to normal idle, and the hissing stopped. This only happens when it's cold......really cold. The only other time it "hisses" noticeably, is in city traffic, slow speed, and around 1400-1500 rpm. When I accelerate or deccelerate, it dissapears.

Anybody else have this occur?
Is this normal?
The truck only has 16K on the ticker.....and other than this, runs like a bat outa you-know-where.....

Steve

 

It is the exhaust back pressure device. It is there to hasten engine warm up for the purpose of getting heat out of the heater sooner. It sounds like it is doing exactly what it is supposed to do.

 

Joe,
Is this normal just on the 99' and newer powerstrokes or is this something on the pre-99 'strokes only?
What other differences are there in the 2 engines?

 

Most of the Power Strokes have the back pressure device. There was one or two years where it could be ordered with or without the back pressure device but I'm pretty sure it was before 1999. Depending on when in 1999 your engine was built, it will have either the early or the newer injectors. If I had your engine serial number I could find out which. The new injectors have a teflon coated barrel and sleeve to abate galling in those areas and the require more oil (volume) which necessitated a higher volume high pressure pump to run them. I think they also increased the horse power rating for 2000 to 250 for the automatics and 275 for the manuals.