coming home today the truck (2004 LB7 stock with Nictane filter) started knocking, sounded like a rod knock on a gas motor. Billowing smoke out when it knocked. If I let off the gas to lower the load, it went away, load it up and it started knocking. Oil pressure30 idling and 60 at 2000RPM. Rough idle too. Kept it up all the way home. No chance I just need to change the nictane is there, about 10,000 miles on the filter, 12500 on the truck, changed the factory filter about 2000 miles ago. I filled it up last night but drove over a 100 miles towing before it started this. Getting ready to go take it to the dealer but thought I would check here first.

On edit - Oil level is fine, doesn't smell like diesel, no SES light on dash

Possibly a bad batch of fuel since you stated you just filled up last night......

Drain the stock filter's fuel into a container and look for contaminents......or water

Is it a place you usually fill up at ?????

If not maybe find someone with a scanner and check your injectors balance rate

T;) NY

It does sound like an injector knock since it goes away with no load. Most likely causes are either bad fuel, injector, or improper timing. Has your oil level gone up any? And it only blows smoke when it knocks? I would get that thing in as soon as you can since you are still under warrenty and you do not want to cause any harm in case it is something serious.

I've filled up at the place a few times, relatively new place in town, fancy place. I did drive off almost 1/2 of the tank before it started doing it, so I was thinking it wasn't the fuel, but don't know. The rough idle felt like a dead cylinder, like when a plug is fouled on a gasser.

Yep, it only blows smoke when it knocks. A couple of times just running about 55 on the highway it would buck hard, knock a few times, and blow smoke with very little load. Oil level looked normal when I checked it after I first noticed the noise.

Of course all this is in the middle of heavy traffic in Dallas, feel sorry for all the people in the cloud behind me. Hope they had their air set on recirculate and not fresh air! :eek:

I also noticed the pilot injection wasn't turning off at higher RPMS like it normally does under a load. With the boat behind it, the knocking and smoking was really bad. I dropped it off at the dealer, on the way without the boat (obviously) it didn't knock or smoke as bad, but it still did it under a load. Mostly between 1500 and 2200 RPMs The service manager said the description sounded like an injector, and they didn't have any in stock. They hope to get it in to look at it tomorrow, so I may know something tomorrow evening.

Glad I have an alternate tow vehicle, or I wouldn't be fishing tomorrow! Guess the Jeep is going back into the boat hauling mode again for the weekend.

See the post on LLY section under NEW LLY Knocks & Smokes. Had the same problem. It smokes so much, you can not see the car behind you. It is definatly fuel related. Added fuel conditioner & never came back.

Thanks for the suggestion Duramax 1, Been running stanadyne lubricity since about 2500 miles, and had it in the last tank of fuel too. I saw the problems in that post earlier when I did a search, it does sound very similar. Maybe it is fuel. The Dealer looked at it today, (called my wife, I was fishing) and said the didn't figure it out yet, need to send some data to GM Monday for help. I didn't get to ask them any questions since they called my wife, have to wait till Monday to find out anything new.

couyld be fuel we had that in summer on a trip started knocking and running rough and smoking real bad got fuel drained and changed filter all was good again

ouers started knocking just under 1/2 tank they thought thieer might have been gas in it if we would have been mome i would have drained it my self but were towing also so couldnt take the chance of losing power on a hill cost us$ 250 to take it out

Hmmm, sounds exactly like mine. about 1/2 tank is where it started. It took 23 gallons to fill it up the night before, so I just don't understand if it was fuel why it wouldn't have shown up right off the bat, or at least before 1/2 tank was gone?

no it will kind of seperate then show up later if its gas you could keep mixing it and run it out but should maybye drain most of it out would be better if you leave it in put alot of lube in take some and see if you can smell gas in it next to us was a moterhome filling up tohe was a t$159 and still filling up poor guy

New sponsor here, best to treat each tank with FP. Fuel quailty has declined greatly and FP will compensate for that. LC in oil will help as well. UOA's back that up.

Fuel quailty article http://www.jsonline.com/news/metro/dec04/283160.asp

Discussion on FP and LC, http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=forum;f=5 run a search and see what others say.

Jeff

Diagnosis was injectors from the Dealer, it should be done tomorrow afternoon. They are installing all 8. Guess the secondary filtration and added lubricity with Stanadyne for the most of the life of this motor didn't save it from the GM injector issues. But of course, it remains to be seen if the injectors were the problem or a misdiagnosis.

well srod look at it this way at least youer getting them changed i still have to worry about mine

Only two were replaced #2 and #4. I picked it up this evening. Seemed to run fine, no issues, will take it on a more extended test drive later in the week. They changed oil and filter too. Guess my wife misunderstood them when she talked with them Monday on how many they were replacing. I wouldn't be surprised if there are more problems in the future since only 2 were replaced, but time will tell.

My attitude does that if i try to adjust the low boost fueling while driving. Puts me on the side of the road to turn the truck off and reset it.Smokes like hell though.

Only two were replaced #2 and #4. I picked it up this evening. Seemed to run fine, no issues, will take it on a more extended test drive later in the week. They changed oil and filter too. Guess my wife misunderstood them when she talked with them Monday on how many they were replacing. I wouldn't be surprised if there are more problems in the future since only 2 were replaced, but time will tell.

Hi srode,
I have the same truck and it has been having the same problem from about 1500 miles. Lots of Knock and lots of White smoke. i have 9,000 miles on it now and it has done it about 4 times. the dealer here in Vacacille first say its fuel and just drive it and did not even wright it up. the last time it did it i made them write a work order and they download the chip bla,bla, bla.... each time it happens it does not set the trouble light so it must be all in my head. Well yesterday it did it again real bad and cars behind me where stoping but i kept going like they told me. finally the engine lite came on and the truck just limped home. i called and had them tow it to the dealer. i will come back and post what they do.

CrazyRider 2004 LLY stock

If it is fuel related, you could always try some Stanadyne to see if it fixes it. I had it happen once to me and the Stanadyne did fix it. Plus I went to the station where I got the fuel at and let them know of the S***ty fuel that they were dispensing. needless to say, there pumps died on them, most likely waxed over filters at the pump. I did change my fuel filter for safe measures later that day.But I will not run a tank without an additive nowadays. I now changed my fuel filter yesterday and trhere is no mroe rust particles found. After 2 filter changes and several tank fulls. I am very careful about where I buy fuel these days.

Only two were replaced #2 and #4. I picked it up this evening. Seemed to run fine, no issues, will take it on a more extended test drive later in the week. They changed oil and filter too. Guess my wife misunderstood them when she talked with them Monday on how many they were replacing. I wouldn't be surprised if there are more problems in the future since only 2 were replaced, but time will tell.

Hi srode,
I have the same truck and it has been having the same problem from about 1500 miles. Lots of Knock and lots of White smoke. i have 9,000 miles on it now and it has done it about 4 times. the dealer here in Vacacille first say its fuel and just drive it and did not even wright it up. the last time it did it i made them write a work order and they download the chip bla,bla, bla.... each time it happens it does not set the trouble light so it must be all in my head. Well yesterday it did it again real bad and cars behind me where stoping but i kept going like they told me. finally the engine lite came on and the truck just limped home. i called and had them tow it to the dealer. i will come back and post what they do.

CrazyRider 2004 LLY stock
Let us know what they find, I am betting injectors.

Mr. Strode,
I am running the same rig as you, 04, Nicktane and Standyne, now at 21000 with no problems (yet?) What is your mileage ? I thought GM was replacing all 8 injectors at a time if any are found bad ?

Only two were replaced #2 and #4. I picked it up this evening. Seemed to run fine, no issues, will take it on a more extended test drive later in the week. They changed oil and filter too. Guess my wife misunderstood them when she talked with them Monday on how many they were replacing. I wouldn't be surprised if there are more problems in the future since only 2 were replaced, but time will tell.

Hi srode,
I have the same truck and it has been having the same problem from about 1500 miles. Lots of Knock and lots of White smoke. i have 9,000 miles on it now and it has done it about 4 times. the dealer here in Vacacille first say its fuel and just drive it and did not even wright it up. the last time it did it i made them write a work order and they download the chip bla,bla, bla.... each time it happens it does not set the trouble light so it must be all in my head. Well yesterday it did it again real bad and cars behind me where stoping but i kept going like they told me. finally the engine lite came on and the truck just limped home. i called and had them tow it to the dealer. i will come back and post what they do.

CrazyRider 2004 LLY stock
Im back... I visited my Vacaville GMC dealer every day to see what they found. On Monday they said they didnt find any problems except the code that was set. i didnt see the code number but the service guy Mike told me it was from low fuel pressure. I asked them to keep it and let someone drive it for a few days to see if they could catch it. I stoped to check on Tuesday and Wednesday and they said they called the factory and are waiting for a call. On thursday they told me they did get it to smoke and knock.
Im not as Crazy as i thought :duh:
Finally on Friday Mike said 3 injectors are bad and GM has agreed to replace them. They should be here in about a week. Yea i said , im leaving on a 2000 mile trip in 4 days. I asked if they could next day the injectors to get it done for my trip or get me a rental. He said the injectors have to be released by GM and i could not even buy them. "They are a controled Part"??
So i went on my way.. I then called GM customer service and told my story. I explained the need for the fast release and shipping and offered to pay to get it. He was great! Put me on hold for a while then came back and said he talked to the Dealer Service manager and the injectors will be there monday and they will have my truck done Tuesday. Later that day i got a phone message from Mike at Vacaville GMC comfirming what GM had said.
I am unhappy the injectors failed on my $47,000 truck. I am happy with the service GM and Vacaville has giving me.

Mr. Strode,
I am running the same rig as you, 04, Nicktane and Standyne, now at 21000 with no problems (yet?) What is your mileage ? I thought GM was replacing all 8 injectors at a time if any are found bad ?At the time of the failure, mileage was about 12,700. Not sure if they replace all 8 all the time or if that's just on the 2001/2002s that got the extended warranty. Are you getting all 8? I was pretty happy to have the truck turned around in 3 days from the drop off. Would have prefered all 8 but if it took a week to get the 8, 2 is fine with me to get it done quick. We use the truck for business, don't need it sitting for a week, plus it's got another 88,000 miles on the warranty, if the other ones are bad, they will show up before then hopefully.

Crazyrider, what was your build date? We might have motors from the same batch of injectors that might be bad.

I am at work so dont have that info but it was at the end of 04. The dealer finally found 3 bad injectors and did a great job getting them replaced after i called GM Customer service. They told me it was electronic and bad or dirty fuel was not a factor ??? I just got back from a 1400 mile trip from Dixon to LA to Death Valley, Reno, then Home and it ran great. It seamed like there was more noize from injectors but engine was good, no smoke or knock.

I did have a problem. The Brake/Steering Hyd assist housing broke with a bang and I had to drive with out it. That was an adventure but I did not want to leave my trailer in the middle of Death Valley. I Posted this problem under LLY.