I had a rattle at part throttle with the engine under moderate load. It sounded light & metallic. The pitch sounded weakly related to the engine RPM. And it wouldn't rattle at idle.

Drove Me NUTS.

Tried many things (octane boost, new fuel filter, pull muffler, replace a cat, pull muffler heat shields, wedge cat heatshields, pull flywheel inspection plate cover, ...) with no luck. FINALLY tracked it down to the EGR tube (thanks Red-Star!).

The EGR tube has an insert inside it that creates a pressure drop so a sensor can measure the exhaust flow thru the EGR tube. The insert is **supposed** to be crimped in place. They miss sometimes.

To check it out, tap the tube and listen for a metallic rattle. Or pull it out and do the same outside of the truck - just be sure to hold the nuts on the end of the tube so they don't make noise and throw you off. You should be able to hear a metallic rattle if the EGR tube is the source. The insert is crimped in right between the two smaller pressure sensing tubes that are welded to the EGR tube.

(The EGR tube runs from the exhaust manifold on the drivers side to the EGR valve which hangs off the back of the supercharger inlet.)

I couldn't get it to rattle in park/neutral or in gear at idle, so debugging it was a nightmare. I was finally able to duplicate it by jacking up the rear wheels and having a buddy work the gas/brake to put some load on the engine and get the RPM up. Then, after making sure to point the truck facing OUT of the garage, I could get under the hood and listen to track it down. Not the safest technique in the world, but desperate times...

Life is good again! Thanks to Red for all the help - not many guys will kill a Saturday to track down a rattle on someone else's ride.

 

Good story! We stick togather.

 

Maybe thats the rattle I get on a cold 1-2 shift? Thanks I will check that out.

 

+1

Looks like I know what I'm doing tomorrow when I get home from work lol.

 

How'd you fix it?

--Daniel