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I have a 99 F350 with a 7.3L Power Stroke turbo diesel. when I accelerate to a steady RPM I hear a hissing sound like air is being released. At the same time the engine seems to lose power and the rpm's drop. This happens anytime i hold a steady rpm weather driving or in park. If I accelerate it stops until the RPM's hold steady again. Also, on an immediate cold start it doesnt seem to do it. After 30 seconds or so, as the engine warms up the problem appears. Does anyone know whats wrong? Any feedback is greatly appreciated.
It is your Exhaust Back Pressure valve. It closes when the truck is cold. Normal operation when the oil temp is below a set point. Let the truck warm up more before driving it and you should not see it when driving.
If its still doing it when on the road and warm then the EBP sensor is most likely plugged. Clean the tube and or replace the sensor.
I will check it out, thanks. It feels like a valve or sensor operating incorrectly. Could this problem be anything other than the mentioned ebp valve considering the symptoms? Thanks for the help everyone.
If it was a sensor I would think you have a check engine lite! Just to be safe get your truck scanned and check for codes. Im not sure about your mechanic ability but yes the exhaust warm up valve can stick shut and cause problems like low power.
I have been having the same problem. When I am at a constant speed on the freeway the boost pressure goes way down to like 1psi but when the engine gets up to temp it goes away. It has more of the hissing sound while in town when the engine is at lower RPM but only while at constant throttle. It goes away when I am completely off throttle or when I accelerate. It was a big problem up untill last week when it got up to 50+ outside and then it did not happen. It is probably the EBP sensor and I will be cleaning it out in the next weekend or 2.
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