Chevy and GMC Duramax Diesel Forum banner

1 - 2 of 2 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Ok guys I have a lly thats bone stock. 175000 miles on the truck. I have a random knock that sounds like a bad injector. The conditions have to be just right for it to knock. Light throttle and cruising down the road. Even then it doesnt happen all the time but is becoming more frequent. Get on it and it goes away but the engine still sounds rough and im a little low on power it seems from when i bought the truck. Almost drives like a gasser when pulling my landscaping equipment. Awhile back i had some surging problems and was pretty sure it was the fpr. I just got to changing the fpr hoping it would also stop the knock as a bonus. It did not but the truck idles much better. Today hooked up the gm tech 2 and main injection rate was 9.5-10 which i understand is what it is suppose to be on a lly. I then checked balance rates and 4 were close to 0. #1 was around -2. #2 was -1.5. #4 was -2.5. #5 was 3.7. #8 was 3. All within spec during idle. The actually got better while in gear. I then raised the rail pressure from 37 to 50. I could hear the knock when doing this. Went back to the balance rates while fuel rail pressure is at 50 and all where within +-4 expect cylinder 5 which went up to 5. Ive heard that a leaking or stuck injector will show up better with the rail pressure raised. My question is, is this enough data to determine that # 5 injector is bad?
 

·
Premium Member
Joined
·
3,256 Posts
I have a similar issue, changed one injector that had a slightly high+ balance rate, but knock came back in a few weeks. I'm thinking it's time for new injectors, just don't seem to have the time....or $$$ right now. I tried numerous different additives and found that Hot Shot Diesel Extreme will quiet things down and noticeably improve power, but the real fix is going to be injectors. If you haven't already done so, you might clean and pick the injector connections.
 
1 - 2 of 2 Posts
Top