My 99 F350 diesel has developed a problem when cold. It looses 90% of it's power and sounds like the exhaust is blocked off (just like a plugged up cat. converter). Once its warm it is fine. 4" exhaust turbo back and no restrictions. Thinking maybe the waste gate is messing up? Selinoid not opening for vacuum to travel to actuator? What tells this to open and close? Problem comes and goes while driving until its completly warm. Ideas?

 

Probably more the Exhaust Back Pressure Valve...

Its normal for the EBP regulator valve to close to aid in coolant/cab heating during low load, low speed engine conditions when ambient air temperature is below 45° and engine oil temperature is below 167°.. The EBP valve is PCM contolled and signaled with imputs from the EOT (engine oil temp sensor) IAT (intake air temp sensor) and in conjuction with exhaust back pressure sensor determine the Back Pressure Valve operation..

An open/shorted EBP sensor will disable the Back Pressure valves operation, but a out of range EOT, IAT 'might' signal a faulty imput.. Could be a sticking valve as well, but if it follows a regular pattern then it may not be a hanging/stuck valve .. If no DTC's/CEL are indicated, as a first step it should be scanned for codes, and matched PIDS (scanner data stream infomation/parameter info. display) for cold operation to varify normal sensors ranges or at least give an indication of whats it's not... Could be that the PCM is seeing a colder operating condition even when warmed, and is comanding the valve to close...

 

Thanks for the info. Sounds right on the money. I'll have a friend scan it for me.

 

you can unplug your EBPV to see if that is the problem. there is a plug in front and a little to the right of the turbo. It is the only two wire plug. Try unpluging that and see if it fixes your problem. It will take a little longer for your truck to warm up with it unpluged, but your truck will run fine. I have had mine unpluged for quite awhile.