I have been noticing an odd noise occasionally after starting the engine. It seems to only happen when it's cold out and being started the first time for the day. it will crank just fine it does puff a cloud of white smoke at fist but starts and idles fine. About 30 seconds after starting the idle jumps to about 1000 rpm it normally idles around 800. When the idle jumps a whistle/squeak begins but intermittently it seems to be pulsing and the noise is heard throughout the exhaust system so I'm thinking its coming from the turbo. Immediately after each pulse the idle surges to about 1200 rpm momentarily and then drops back to about 1000. This happens every couple seconds and each time it happens a slight puff of white smoke come from the tail pipe. After about five min it all stops idle drops back to normal about 800 rpm range and no other issues. I can't figure out what it is or if it's normal I don't think it's normal though. I just purchased this truck so I don't know how long this has been going on and not every morning is cold here yet so it's been hard to narrow down exactly what's happening. Anyone have any ideas?

 

sounds like the EBPV is confused. do you have a way to get codes?
you may need to check the EBP see link.
Welcome to guzzle's Exhaust Backpressure Sensor Cleaning Maintenance Web Page

 

There is a ebpv on the exit of the turbo. When its cold it closes to help heat up the motor. When the oil gets a certain temp it stays open and thats that. You can unplug it at the base of the turbo or put in a delete pedestal. Not a problem unless you start to drive off to soon, you will have a lack of power. I generally let mine idle long enough that it is off before I drive away. Here in Calif. I have never had a problem. In Wyoming, well its best to just wait.
Chet

 

The pulsing usually happens when the air or oil temp is right at the cut off when idling. Driving it keeps it from sitting at this point.