Can you help me I.D. engine knocking sound?

[wheeler]

Drove 1000 miles in last two days w/ my '03 Chevy 2500HD D/A (Banks exhaust brake, No Juice yet) this time NOT pulling the fifth wheel, and after two hours on the highway around 70 mph my truck had an intermittent knocking or clattering sound along with a loss of power. The sound seemed to come from center just beneath and in front of my feet.

At first it seemed related to slight changes in road surface (like go over a dip and that would initiate this problem), or possibly related to when I removed my foot from the accelerator-- you'd get this sort of rubbing sound and stumbling loss of power from the engine, like "Are we going to stall out?" The problem would last 10 seconds tops then the engine would come back and run normally for fifteen minutes then do it again.

Called OnStar and they did a diagnostic while I was driving and they found no error codes reported.

I stopped for an hour for dinner, then resumed my trip for 800 miles and it never happened again. This symptom didn't ring a bell to my dealer/service advisor and now truck is not exhibiting the problem-- but it was pretty disturbing. (I have had intermittent problem with all my dash gauges reading zero, then next start they're fine-- maybe an electronic glitch?) Any ideas? Thanks. --wheeler [img]smile.gif[/img]

[JimWilson]

I wonder if you have some type of grounding problem. All kinds of weird sh#t can happen when there's a flaky ground.

[blakmax]

Mine did it too! At about 10,000 miles i had traveled from Colorado to San Diego. The Mexican border control would not let me cross. Heading to another border crossing, my engine started "racking" and the service engine soon light came on. Scared me to the point of getting the truck and trailer off the highway.I thought the motor had serious problems,cycled the ignition on/off and engine ran fine! I have more than 25,000 miles now, and it never happened since.I have the equipment to scan the ECM, but by the time our trip ended, nothing was in freeze frame history.I also lost power.Fuel?Computer?

[wheeler]

Thanks guys I'll check the ground connection, among other things. The misfiring engine sound and stumbling power along with the intermittent nature made me think of a fuel filter problem, but the dealer didn't seem to suspect the fuel filter. Have not had truck checked out yet-- as I said, the problem is not occuring now or in last 800 miles. Any different ideas? Thanks. --wheeler
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[crashdnt]

I have had a similar noise many times. It turned out to be a bad injector. It was on and off, and very loud at idle. The SES light never came on, and the dealer did not find it the first visit. They even dropped the oil pan to check the bottom end. That was 1 1/2 years, and 5000 miles ago. Four injectors later I still keep waiting to hear my noise again. Good Luck