Engine knock

[dave16405]

I have a 2002 Chevy 2500HD with the Duramax. Last fall it started to knock under certain loads at around 1800 to 2000 rpms. I have had it to a dealer that checked the injector balance. There were four injectors that looked bad. He noticed that the engine was at 175 degrees. He replaced the thermostats. The temperature is now more normal and the injector balance is good but the knock is still there and louder that last fall. Do all injector problems show up with electronic testing? It is at a GMC dealer now. They confirm that the balance is good. They think that it is because the engine has 94000 miles on it. I have sampled the oil every 10000 miles since the engine was new and nothing has ever showed up indicating excessive wear. I think that the engine should be a long way from wearing out. On occasion, the engine has missed a little and I have seen smoke when sitting at a stop light. When the knock first started, it only happened once and a while. Now it happens everytime I go up a hill especially in third or fourth gear. I know that this subject has been addressed before and I have read all of the posts that I could find. I just can't seem to get a dealer to take my problem seriously or at least believe that my normally quiet engine has an abnormal noise. Does anyone have any ideas?

[More Power]

A dealer mechanic can use a Tech II scan tool to selectively disable each injector - one at a time. This'll allow you (or the mechanic) to tell whether the knock is injector related, whether testing is performed in the shop or during a drive.

Jim

[SoTxPollock]

You don't suppose they are trying to stall for about 6000 more miles before they diagnose the problem do you? Especially if its something with the rotating assembly of the engine and not injectors.

[kerryw]

have seen 2002 with knock which turned out to be torque converter bolts , noise telegrafted to engine .

[D-max Man]

I have seen a bad fuel injection control module (FICM) cause an engine to become lauder only in a certain RPM range before. GM actually bought the truck back before they got it figured out.

It would run quietly below and above that range. It turned out that the FICM was shutting down the pilot injection during that range and then turning it back on again until 2,500 rpm (Where it is supposed to turn off).