PSD Hissing when cold
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From: Texas
PSD Hissing when cold
I'm a naturally aspirated GM Diesel convert. I have an early 1999 350 Crew Cab PSD. It is my first time to run this truck in cold weather(32-36 Degrees F.) This morning, I noted that the truck at various speeds would hiss and release. Each time it hissed, the RPM's would drop some 50-100. The truck would surge with the drop and increase in RPM's. After it warmed up the surging and hissing disappeared. After the truck set out exposed to the same temps, it did it again (even with the cruise set). I have 90,000 miles on the truck and have had the fluids recently changed. Please help me to decide if I need service or if I could check some things.
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100% normal. On the 7.3s, Ford uses the Exhaust Backpressure Valve to force the engine to warm up faster. With enough throttle, they back off on closing it so as not to totally kill the power of the truck. With little enough throttle you don't really notice it. It's that whole range in between where the noise and lag gets exciting until the truck gets warm enough for it to just stay open. You get on it enough to get the EBV to open up and then all of a sudden the backpressure goes awayand you're zoooooming! So you let off the throttle a little bit and it closes and again and all of a sudden it's like driving in Jello. So you give it more throttle and it opens.... well, you see where this is headed.
Duncan
Duncan
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From: Texas
Thank you to both of you for the response. I have noted the speed up thing and it was exactly as you stated. I'll also check the boots. I noticed the previous owner had replaced two of the boots and may not have tightened them under cooler conditions.
This is a great site. Again, thanx for the input.
This is a great site. Again, thanx for the input.
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