I have read, and read, and read some more about injector issues. The questions I have

If you have bad injectors can you replace just the tips, or is it better to replace the whole injector?

If you have bought your fuel from the same spot the majority of the time, how can your fuel mileage jump so dramatically, but not have an affect on driveability

And why so much for an injector? especially a reman one.

I bought this truck with 99000 miles on it I have roughly 125000 on it now over 2 years. The truck came with 265/75/16 10 ply tires on it. It was nothing to be running 15-16 mpg locally, if I kept it under 70 on the highway it was 18-20 mpg. Now I am lucky to get 15 mpg on the highway. It runs good, no excessive smoking, you can see a little at full throttle. It smells a little at idle but nothing thats is too harsh.

I am lost here still. help

Whole injector gets replaced.
Its a hard part to make with very tight clearances etc. lly's do not as a rule have injector issues as the lb7s have.

Still really doesn't answer my question of the significant drop in fuel mileage, and I see these ads for replacement injector nozzles or tips what do they do? Or am I barking up the wrong tree, should I be looking elsewhere for my fuel mileage?

Well I found today that, my truck is smoking when its cold. When it kicks up on the elevated idle, it has a faint cloud of blue smoke, and when it warms up it turns to black, but the only time i see it is when it is above idle. Any Ideas?

How cold are you talking about? When it's 25F or colder, I'll bet you that all of these duramax engines that are still mostly stock configured will show some slight blueish/grayish tinted smoke during high idel warm up. And the colder it is, the more you'll see. A light amount of smoke at high idel is normal and not even worth factoring in to your concerns anymore.
Regarding the gas mileage, are you sure you haven't changed your driving style. Did you get a performace programmer and you're putting your foot into it a little more now? Have you cleaned your injectors at all? Have you changed your fuel filter yet? Also, the mileage is reflected very much so in the highway speeds you drive. 70 mph and about 2100-2200 rpm (if you have the 5 speed allison) your walking a fine line as to a pretty substantual decrease in MPG per mph you accelerate to. This is while not hauling or towing anything. Forget it if you've got 8000 lbs or more behind you, your mileage will be comperable to a 34 foot boat!! Try to keep your rpms under 2000 during acceleration and highway driving and see what you get.

Still really doesn't answer my question of the significant drop in fuel mileage, and I see these ads for replacement injector nozzles or tips what do they do? Or am I barking up the wrong tree, should I be looking elsewhere for my fuel mileage?

You state "significant" - can you quantify what you're referring to? Can you describe something like "18-20MPG summer vs. 16-19 winter"?

You should be aware winter blends of diesel fuel will always give somewhat poorer economy than summer blends; couple that with lengthier warm-ups, ie. longer idling, and you can pretty much be assured there's nothing "wrong" with your vehicle.

X2 & Check the simple things like filtration Air,Fuel make sure they are clean

You show that you have a K&N air filter-- is it a oiled filter-- it is possible that the MAF sensor has oil on it and then is dirty with intake dust. Common problem with K&N filters. Suggest you clean it with the special cleaner available at most auto parts stores.

I change the fuel filter everytime the oil is changed, approx 4000-4500 miles or 3 months whichever comes first. Air filter has been changed every other. I have no programmer, everything is bone stock except the exhaust. Mileage drops were before it got cold, I am also very aware of the 2000 rpm rule. The only thing that I changed is the tires, the truck had 265/75/16 10 ply tires on it when I bought it, I replaced them with the same size and tread style tire, and ply rating. As far as the cold I understand that blended fuel will make a difference, and I will let the truck run for no more than 10 mins before I leave.

I also have cleaned the MAF 4-5 times with the CRC cleaner

When I first noticed the Significant drop was back this summer, when we went on Vacation. I had a cap on the back covering about 1200 lbs of "stuff" clothes, sleeping bags, bikes, food. 6 people and a 20 lb chocolate lab. I kept the cruise at 65, until I got on the Northway and ran 70 for about 20 miles. Went to Vermont, around the Bennington area. Its about a 200 miles one way, by the time I got there I had to fuel, just to get around. And barely made it home on that fill up?

this last tank of fuel i got 13.7 mpg on the highway, with the cruise set at 63 mph which still leaves a few hundred rpm to go, before it reaches 2000rpm

Hello,

Do you use any additives to help keep the fuel system working at optimum efficeincy, have you changed your lubs wherever they are fluid, ex. Trans, rear, front diff. ?. Is the engine running any rougher or louder since you purchased it ? If you can get some well made bio diesel pour it into the fuel system and it will clean and lubricate everything ( expect to change a fuel filter ). It sounds to me like your not getting an even spray from the injectors. You can try a good injector cleaner and that should give some indication of what it might be.

Can you get in touch with the person who owned it before you and find out what maintenance he performed. Last, if you can't find out anything just keep it running until whatever is giving you the bad fuel milage becomes more pronounced.

Hope this helps

Ken

i just switched to the Rotella 5-40 synthetic oil, new fuel filter, fuel treated with lucas oil and Z-max fueled it today and had a hand calculated mileage of 14.2 mpg.

Get the balance rates on your injectors looked at. That will give you a general idea as to what shape they are in. This will eliminate them as the problem.

I had same problem with same question last summer. Ran two tanks of B20 through and a new filter. Mileage was back to normal. I run B20 right before FF change, every 10K. Winter fuel sucks for mileage. Also ckeck your fuel return cooler for caked on dirt.

I had same problem with same question last summer. Ran two tanks of B20 through and a new filter. Mileage was back to normal. I run B20 right before FF change, every 10K. Winter fuel sucks for mileage. Also ckeck your fuel return cooler for caked on dirt.

Where is this fuel return cooler?

Where is this fuel return cooler?

Located under the truck, in front of the fuel tank. Looks like a small radiator. :)

does this "cool" return fuel or supply fuel. Are these prone to plugging or making any noise?

Interestingly I have the same symptoms, 3-5 mpg lower (used to get about 22mpg @ 60mph, now it's around 18/19. I pay a lot of attention to the air filter, maf sensor, tires and any other factors. (One time I caught the parking brake sticking!)

Then one day my wife was driving and I got a chance to watch the exhaust closely, it would puff a little black smoke but intermittantly like it was one or two cylinders.

I havn't had the injectors looked at yet but they are first on the list.

'05 lly with 153,000 miles

Its not unusual for any and all diesels smoke when its bitter cold, especially when you first start it up. When I had my 04 and I was living in Syracuse, it would smoke pretty good when the high idle was engaged. I was also running between Hypertech and the Predator. My mileage always took a crap during the winter, as does everyone's up north.

Are you running the winter cover? If not, that will make a difference with efficiency of the engine, especially with the temps you guys are seeing lately. A warmed up engine performs more efficient than one thats not running at the optimum temp. Basically, you're supposed to get better mileage with it warmed up. Now, I realize they will never fully warm up this time of year but the covers certainly help. I dont know how anyone actually got any heat inside the cab when they werent running the cover below 20 degrees.

When I traded in, I moved to Watertown and my mileage was just as horrendous during the winter months as well. High idle does suck down fuel. While idling dosent burn much fuel at its normal rpm, 1250 rpms is a whole 'nuther ball game when it comes to fuel consumption. The winter blended mixes up there are generally 75% diesel, 5% additives and 20% kerosene. The further north you go, the more they cut it with kerosene, dropping your mileage. When kero burns, it burns with less btu's and dosent generate as much heat and power as regular #2 diesel. Its just a fact of life up there.

Also, I would say its pretty rare that LLY injectors go bad. I've been around this forum for a long time and have only heard of a small handful of people with bad injectors on LLY's, between 04.5 and 05 model years. I know the injector harnesses did plague those model years but not necessarily injectors. A fuel additive is also a must for you guys up there. I ran a bottle of Stanadyne in every tank. Its a simple piece of mind.

If you're changing your fuel filter at around every 5000 miles, that shouldnt be the problem. Winter fuel sucks, extended high idle time, and ridiculous temps are whats probably causing your mileage drop, plain and simple. It also wouldnt hurt to throw away that K&N. Not many people here use them, and even less after that extensive air filter study came out, showing how worthless they are. If you have a stock ac delco filter laying around, I would try putting that back in it.

You could also try to do the air box mod that was very common on LLY engines, which opens up the air box to help the engine breath easier.

If you're still having problems, bring it to the dealer and have them test your injector's balance rates. If a couple are low, that could also be your problem. I'd be interested to know what the outcome is. Or if you dont want to spend the money at the stealership, and none of blame you for not wanting to, find someone in your area who's got a programmer that can read your balance rates for you. Depending on where you are in the state, I know of a few who may be local to you who could do this for you.

I know that cold weather is a factor in less MPG's, but this problem has been ongoing since July. I have gained back at most 2mpg, but now I am back down to 10-11 mpg. I just put the KN just before Thanksgiving and have been using Lucas fuel treatment. I did switch to the 5w40 synthetic Rotella. I change the fuel filter with every oil change and have never had the water in fuel light come on at all since I have owned the truck. It has never left me stranded, but I can only get 225-250 miles out of a fill up. ANd @ 2.70 per gallon its breaking me. I love the truck but man. I bought a commuter car for 500 bucks and put another 200 to get to pass inspection, 97 Buick LeSabre with 215000 miles on it and this thing gets almost 28 mpg still!!!! go figure! I am almost thinking about trading it for a SRW F350 thats how irritated I am.

I wouldnt expect much better mileage with a Ford. They are nice trucks but I hear the mileage pretty much sucks ass.

I see you're running 5w40. I'm not an oil guy by any means but this is not the correct weight for you. What you're running is designed for super, arctic climates. I was running that as well and burning up to 3 quarts between changes. While it does provide protection, it isnt the right oil for you. I have run Rotella in the past but a 15 weight is all that we really need and it will offer protection in colder temps than upstate NY will ever see.

If you're interested, a friend of mine is an oil god. He works for Amsoil. I'm not trying to sell you on any Amsoil product because I dont run it myself either, but he knows his shit when it comes to the weight that we need to be running. That could have an effect on your performance.

http://dieseltowingresource.com/showthread.php?t=1205

His name is Ashton and he lives in Pennsylvania. He's only a phone call away and you'd be amazed at what he could tell you about oil and other lubricants. He goes by the name of Wrecker at the bottom of that page.

I was running 15w40 delo 500, based on a recommendation from a friend of mine who used it in his 300 6cyl ford f150 and he ended up with 350000 miles on it before it ended up with the NYS road cancer that ate the frame up. We have a f350 at work that has been a propane service truck for all its life and that has 250000 miles on it and according to all of the service records all its had in it is the 5w40 synthetic so thats where I got the idea from to try. So far I have had no problems or consumption, and its been 1500 miles since I changed over. And yes today was 15 below 0 and it started right up with no block heat or extra electricity. And I don't think that I could have my name on a title that a ford brand on it LOL

i just had 2 injectors replaced on mine, only symptom was a shake just off idle and a barely noticable fuel knock.niether was very noticable but, now she is purring like a kitten.

From what I have been told and seen it sounds somewhat normal. I notice a nice drop in fuel economy when it gets cold. I also notice some change from tank to tank depending on where I buy it. I have been told the tire size even though not that much bigger than stock plays a bigger role than we would think in decreasing the fuel economy. As for the somking I have found out that most of these trucks do it to some extent when it gets cold. Nothing to ground breaking here just letting you know I see similar stuff with mine and with some of my friends trucks.

From what I have been told and seen it sounds somewhat normal. I notice a nice drop in fuel economy when it gets cold. I also notice some change from tank to tank depending on where I buy it. I have been told the tire size even though not that much bigger than stock plays a bigger role than we would think in decreasing the fuel economy. As for the somking I have found out that most of these trucks do it to some extent when it gets cold. Nothing to ground breaking here just letting you know I see similar stuff with mine and with some of my friends trucks.


I have been having this problem since July

Well, it has been awhile so I will post this for information to all of you. I finally found my mileage drop, the majority of it at least. It has been a few months since I tried this and so far it has been great. I was told by a friend of mine, one day after discussing this whole thing. He has a 07? f350 with the 6.0L. He was using the Lucas Fuel Injector Treatment as well. He started to have major starting issues with his truck, even when it was warm. And lost about 4mpg at the end. He took it to a prominent diesel repair shop, and found that 2 of his injectors were no good. They linked it to the LUCAS Fuel Injection Treatment. After I heard his story, I quit using it to see what would happen. I fueled at the begining of the week without it, by the end of the week I refueled after 250 miles (still had between 1/2 and 1/4 of a tank) I had gained 2mpg. 13 mpg. The next day I went to Ohio and picked up the neighbor kids Bronco II. I got 13.5 mpg loaded on the way back doing 75 mph!!!! I went through 4 tankfulls of fuel that day to do about 1200 miles. I have since stopped using this LUCAS Fuel Treatment. I have gone back to Power Service. I did email LUCAS and recieved no reply from them. FYI

I was getting 17.3 mpg interstate on stock everything I was using ps and then started using lucas and seen it drop to 15.5 over the same exact road !!ever since I have seen my mileage fluctuate from 16.5 to 17.5. I wanted more so I bought a ppe standard and used their recomended 90 hp tune and am still only getting 16.5 to 17 ??go figure!the best that I got before I ran lucas was 19 hand cal all my mileage!I tried a 8 hr bully dog that was supposed to erase itself off!!now I have learned that bulldog may contribute to my crappy mileage!

there is a really good sticky in the maintenance section, see how Lucas did.......as for the PPE and mileage.....it went further south, no improvement, no help when I called. When they ran out of options (tried every level 1-5), they asked who I bought it from....and then said call them.