I did a search to find if there was a similar thread and found one but after I poseted realized it was in the LB7 forum so I thought I would re-post here.


I noticed the knock at about 1100 miles. It happens only when under load. If I let up slightly on the gas it goes away. Most noticeable when on the freeway at about 65. Definitely way before 2500/2600 rpm. I'll hear it easily at 2000 rpm and below.


I took it to the dealer. After the first day they thought it was a bad injector. After the second day they said it was throwing two codes, one for the turbo and one for the egr but the service manager did not have the code numbers. This is the third day, they just called me and told me the 'EGR control module' wasn't working and needed to be replaced. They told me they were so new they would have to pull one off the line and it would probably take about a week.


They gave me a Envoy as a rental the first day so I'm o.k. with it taking time as long as they fix it right. Also don't want to drive it if that would hurt it. I know knocks are not as bad in diesels ad gassers but it still makes me cringe when I hear it.


I'm new to diesels and the duramax but I've been reading the board heavily for the last couple of months so I've picked up some stuff. This sounds kind of fishy and I asked them why the egr module not working would cause a knock an they just said its possible. Anyone have any ideas?


It runs fine. No black or white smoke. Gets good mileage - 18-20mpg on the highway at 65mph. The coolant temp goes up to a couple lines below 210 and sits there when fully warm on a hot day. Not sure if this good or bad for this engine but I haven't towed anything heavy to see if it goes higher.


Sorry for the long post. Included as much info as possible to try to anticipate any questions.

I did a search to find if there was a similar thread and found one but after I poseted realized it was in the LB7 forum so I thought I would re-post here.


I noticed the knock at about 1100 miles. It happens only when under load. If I let up slightly on the gas it goes away. Most noticeable when on the freeway at about 65. Definitely way before 2500/2600 rpm. I'll hear it easily at 2000 rpm and below.


I took it to the dealer. After the first day they thought it was a bad injector. After the second day they said it was throwing two codes, one for the turbo and one for the egr but the service manager did not have the code numbers. This is the third day, they just called me and told me the 'EGR control module' wasn't working and needed to be replaced. They told me they were so new they would have to pull one off the line and it would probably take about a week.


They gave me a Envoy as a rental the first day so I'm o.k. with it taking time as long as they fix it right. Also don't want to drive it if that would hurt it. I know knocks are not as bad in diesels ad gassers but it still makes me cringe when I hear it.


I'm new to diesels and the duramax but I've been reading the board heavily for the last couple of months so I've picked up some stuff. This sounds kind of fishy and I asked them why the egr module not working would cause a knock an they just said its possible. Anyone have any ideas?


It runs fine. No black or white smoke. Gets good mileage - 18-20mpg on the highway at 65mph. The coolant temp goes up to a couple lines below 210 and sits there when fully warm on a hot day. Not sure if this good or bad for this engine but I haven't towed anything heavy to see if it goes higher.


Sorry for the long post. Included as much info as possible to try to anticipate any questions.<!-- Signature -->


This sounds KINDA similar to mine. However, mine makes a terrible pinging noise with no load.Goes away with load at a higher RPM. AND, smokes white AND Black.

If I gas it, say over 2500 rpm's and accelerate, it seems to dissapear.

Dammit, the truck only has 1650 mi. on it. Am going to got to stealership today and have them test it for codes, etc......

Please let us know the final outcome....

Ironically I bought this truck '04 Silverado which replaced an '03 Envoy. Totaled it with frame damage [not at fault]

Loved the Envoy. Silky SMOOOOOTH I-6.

Kinda sorta also sounds like what happened to us when the selenoid controlling the variable turbo vanes went bad. NOT saying it is, just has the same symptoms. The day the selenoid went (and GM says they will go bad in first 1 to 1500 miles) it was ok in the morning. an hour later I was getting a SES light. Light pedal it was ok, but trying to pull onto xway it knocked rattled smoked, smoked so much the xway traffic thought they were in the middle of a cloud http://dieselplace.com/forum/smileys/HiHi.gif . But that is what happened to us. It seems that injectors, the EGR system and the turbo vane controller can all cause these symptoms

DRCook,


Interesting. They did say there was a code on the turdo and the EGR. No SEs light for me. I might have brought it in before it go too bad. I wonder if I had driven it a while longer if it would have gotten worse and seen some of the stuff you saw.


I'll let the dealer do his stuff and see what happens. I sure hope they hurry up, I miss my truck! I'll let you guys know what happens.


Mark

Well, I got the truck back yesterday.


They replaced the EGR solenoid bacause they said it was bad. The service manager said that should fix the knock. I told him I doubted it and would be back if it didn't. Saw the tech's comment that he was not able to duplicate the knock.


I doubt the service manager knows what he is talking about or what is going on. He even admitted he didn't know much about diesels. When I told him replaceing the EGR solenoid would not fix the knock he went and tog the TSB that lists knock between 1500 - 1800 rpm as normal 'burst rattle'. I asked him to explaind burst rattle and got a 'deer in the headlights look'.


As I was leaving I asked about the ECM flash that just came out and he said 'oh yeah, I forgot to tell you, we did that too' although iot was not on the invoice.


The flash seemed to help. Knock was still there but did not seem as loud. Low speed surge I had also seemed to be gone.


Have to figure out where to go from here. Overall, I was not very impressed with the service. They did give me a rental but they did not seem very capable technically. Will probably go to a different dealer next time. Need to find a good diesel tech.


They did give me the codes it was showing so I can start there.