Knocking at idle

[opiekelly]

Just stop by the dealer today to see what was causing the knocking noise at idle. Diesel Tech listen to the engine and said it was most likely a dirty/clogged injector. It also runs a little ruff at 1300 rpm. He recommended using diesel fuel additive to possibly clean the injectors and if the problem did not clear up an injector replacement would be necessary. He said he has seen this problem at 30,000 miles but none at 9,000. Is this a known problem with the Bosch system? Don't want to be messing with injectors every 30K miles.

[mechanicwillie]

as to your knocking noise i had a 2002 in today with 8697kms on it and it made funny noises.this is normal for this engine.i have not yet replaced a injector on a low km truck for a knocking noise at idle they usaully act up under load.tell the tech to do a balance rate check with the tech 2 you can tell if a injector is bad at idle.they all should read very close to the same. smile.gif

[Kennedy]

Interesting! Mine has always had #6 balancing + 1.8ish and #8 at - 1.8ish. All others +/- .5 or so.

Been waiting to do a set of HP injectors and have them balanced as closely as possible before I do anything...

[opiekelly]

He mentioned putting it on the computer to do a check of the balances. I will probably get Stanadyne and see if it makes a difference. If not I will have it in the shop for a real diagnoses.

[mechanicwillie]

the spec is +/- 2.5 and if the injector reading is on the higher side it is possible on the way out.i am working on a duramax were the readings 6 out of 8 were up at the 3.0 mark.no power and runs like garbage. smile.gif

[PEANUTGRWR]

MINE HAS A KNOCKING SOUND FROM JUST ABOVE IDLE TO 2600 RPMS DO ANY OF YOU HAVE ANY SUGGESTIONS WHAT THIS IS. I KNOW IT HAS SOMETHING TO DO WITH THE PILOT INJECTION BUT IT HAS JUST STARTED THIS RECENTLY.

[mark45678]

YO Pnut turn the gas down! your going hurt the bottom end with all the gas that rockets been burning!!!!! all goofing a side it may have to much timeing or just too much propane at slow engine speeds or a combo of the two!!

[mackin]

PEANUTGRWR,


Now you've gone to far PEANUT....... tongue.gif

Only when cold? Right? With the "JUICE." Me too. Not to worry says the Big GUY at EDGE....... It's a pilot inj. thing ......? All though they did nothing with .... Perhaps a conflict .. . What version are you running ? 3.0? Got to ask the guys with 3.2 if they have this ..... With the 60 HP, It would snarl (pilot inj shut off) between each shift .......

It wouldn't be to much timing unless it is stored setting from shut down, then a correction .... The "JUICE" doesn't come on to full potential till a certain temp is reached, as I understand it ....... It does quickly disappear once it gains a little temp ........So if yours acts like I've explained then YES , me too .......Got Peanuts , Mr. Carter ..........?

MAC



:D :D

[ 06-11-2002: Message edited by: mackin ]</p>

[markf]

mechanicwille

I've got a question regarding engine noise. I am getting a sound from the engine that resembles small arms auto fire that lasts about 1-2 seconds when the transmission is shifting. This only happens when I am punching the pedal hard going uphill or just hauling a$$. It hits at 45 on the speedometer with the RPM between 2800 & 3000. It is right at the shift point and it does not happen during normal sane acceleration. Have you heard of this before? Any ideas?

2002 GMC 3500 CC D/A 4x4
SLT 40/20/40 leather
in the rarely seen pewter/neutral combo
pull a 32' 12,000lb 6 horse trailer

[PEANUTGRWR]

MACKIN, NOOOOOOOO ITS NOT JUICE OR PROPANE RELATED AND DOESNT MATTER IF THE ENGINE IS COLD OR NOT. I FEEL LIKE ITS TIMING BECAUSE ITS DONE IT EVER SINCE MY TRUCK WAS IN THE SHOP. GONNA HEAD THE THE STEALERSHIP SOON TO SEE WHATS UP.

[7mmSTW]

Hey Peanut, your truck seemed to have a little rougher idle than your dads. That may be related.

Later

Seven

[turbowind]

Hi Guys !
A friend of mine with a Duramax has a very loud knock, it comes and goes and is found in the lower RPM range. It is loud enought that people give him a puzzled look when it starts knocking.
He took it to the GMC dealer and the tech was puzzled and agreed this was not a normal sound.
The tech called him today and said GM was aware of this problem...It was an oil delivery problem involving an oil valve in the head or cylinder area... this problem was not a "priority repair" as it does not harm the engine....Does anyone know anything about this ?? Is this tech confusing the "tick tick " problem with this ???

Les

[Kennedy]

markf,

What you are describing sounds like the pilot injection shutting off. This is a normal function and may vary with load, APP, etc.

[mackin]

PEANUTGRWR ,

Ya I noticed mine does it very low in the rpms and when cold only ... Certainly juice related, positive ....... I liked the snarl with the other box between shifts ..... Now it sounds like I got CACKLE ..... This out to stir some CRAP ........ HE HE HEEEEE

MAC tongue.gif

[GMC-2002-Dmax]

kennedy,or anyone else!!!

pilot injector??? :confused: what is the pilot injector and what does it do???

When I punch my truck especially up a hill it seems to take on a different sound between shifts. I don't notice it much when I keep my foot out of it, which is hardly ever.

i have not had any problems at all, no tick, just had the tranny update for busy shifting, but it was doing it before I had it done.\

Thanks in advance :D

GMC

[markf]

Kennedy

Why does the pilot injection shut off? Is it to let more fuel in or to restrict fuel? I need a little "engineering 101" here on this issue. Any additional descriptive info would be appreciated.

Turning to another topic. I am looking at a Fumoto Valve on your site. Doe the valve have a spring in it to keep it locked down so it doesn't pop open?

2002 GMC 3500 CC D/A 4x4
SLT

[opiekelly]

Well I have gone through a tank with the Stanadyne performance fuel additive and the knocking at idle has subsided. Engine runs much smoother.

[SoCalDMAX]

Mark,

Noticed your questions hadn't been answered yet.

1. Pilot injection is a small squirt of fuel just prior to the main squirt (love these technical terms!) which is used to make it the quietest diesel out there. Isuzu discovered that this gave a softer combustion explosion and cuts way down on the diesel rattle. It shuts off at around 2500rpm, based on load and conditions, where you may also feel a slight increase in power. It probably decreases fuel economy by a small amount, but they considered it a good tradeoff.

The Fumoto valve is a solid brass 1/4 turn ball valve with a slot for the handle and a spring loaded detent in the closed position. Lots of people swear they've had no problem with it opening (snagging on brush) but it has happened to a few out in the woods. A lot of people have suggested a zip tie or hose clamp to secure it, sounds good to me.

The Fumoto makes changing oil a real snap, get the one with the hose nipple on it and let it drain while you struggle with the "gorilla installed" self-tightening oil filter.

Now that I saw the suggestion to punch a hole low and high in the oil filter and let it drain into a pan before removal, I think my "oil filter flew off and splattered me" days are over. Or maybe I'm fantasizing.

Oh yeah, Kennedydiesel.com carries the Fumoto valve.

Regards, Steve

[Dietz]

My truck developed a knock "more like a tick to me" at about 700 miles. I changed engine oil at 1000 miles. Knock did not go away. This noise sounded like you were tapping 2 ball bearings together. It only did it at idle at operating temp. Never did it when cold. Raise the rpms a whisper and it would go away. I pulled my 7000 lb. boat on a 140 mile trip and it never did it till I got back home. Next day it did it so I took it to dealer and asked for diesel tech. to listen to it while it was making noise. He sayed it was an injector and he would bet it was #8 and that he just replaced one making same noise. He plugged a diagnostic tool into truck and determined it was #8. He replaced #8 injector the next day and my truck sounds like a duramax again.
600 miles later truck is still quiet and running great. Sorry for the long post but I thought this might help those with knock-tick noises at idle. Pulling over Wolf Creek this weekend,can't wait.

Dietz

[Jimamatic]

Just curious. Which side is #8 on and could changing an injector possibly be the cure for the tick. For Dietz, this tick is very wide spread and has been talked about on many many previous posts.

-------------------
2001 LS 2500hd cc sb D/A

[Dietz]

Jimamatic, #8 injector is on right side if you are sitting in truck. When my truck first started making the noise I thought it was the tick that has been discussed so much on this forum. It didn't sound anything like the sound bit posted here before. Service consultant told me that it was not the "duramax tick"

Dietz

[JLee]

Dietz - is that Wolf Creek as in "Wolf Creek Pass" in Colorado?

[Jimamatic]

Thanks Dietz. Should've known better to think the tick would be something so simple...

[Dietz]

JLee- yep Wolf Creek pass. I live in Colorado Springs. Don't know why I didn't put that in my profile. Sure do hope they don't close the pass because of the fire again. I want to pull the boat over and spend a few days on Lake Navajo.

Dietz

[opiekelly]

Well I took the truck in yesterday and the dealer called me back today and said all the injectors on the left bank "are out of balance". This was causing the knocking at idle. I have seen several post of trucks needing injectors. Has GM ratified the problem or is/was it just a run of bad parts from Bosch? I have also seen post saying the dealers wont replace the injectors due to bad fuel. I have a neighbor with a VW TDI and we use the same fuel station. He has not had problems. I know I am not comparing apples to apples. Luckly my dealer is good and they did not hesitate to fix the problem.

[opiekelly]

Well the dealer replaced 4 injectors and said there was rust on the injectors. I asked why I did not get a "water in fuel" message or why the seperator did not do its job. No real answer to those questions. I took a picture of one of the injectors. http://pub.barnstormdesign.com/duramax/DSCN0025.JPG

Also the truck still knocks at idle when the tranny is in Drive. Going to take it back on Tuesday.