Can't get MPG back

C

cj42

New England Texan
Joined
Mar 8, 2011
Messages
368
Over a year ago my mileage dropped from 19 mpg to 15 mpg. I found that 5 out of 6 injector were bad so I replaced them with Don M 100 HP injectors. Since my truck has over 230,000 it this was my excuse to do some up grades. New CP3 33%, rebuilt tranny, new turbo, larger tires 285's. I was running just a quad race box but after all the mod's I bought a smarty and ran it on sw7 until UDc came out.
I have tried multiple cp3 pumps, multiple pusher pump's, ran stock program, checked brake calipers (found one sticking), jacked up the entire truck to see if we could feel and kind of drag somewhere, replaced crack sensor, replaced air filter, replaced all fuel filters, increased tire air pressure, tried several fuel stations and I am probably forgetting so other stuff we tried. None of this had made a difference. I used to be able to get 580-600 miles on a fill up now the best I have done is 495.. Any other idea's on what to check? I know once winter fuel goes away I will gain a little but looking for some others things to check. In have been wondering about MAP, air intake sensor, intercooled etc.. Also calibrated my speedo, using ggps, road markers and I'm have it so the truck is going about.5 mph faster then speedo. Thanks guys
 
It's the injectors. I'm in the same boat! I run stupid timing in the 2000rpm range to make better mileage. Your going to have to tell me about that crack sensor! Is that on the rods?LOL:kick: Happy New Year!
 
I don't think its the injectors since I just replaced them. Plenty of guys are running 100's and getting good mileage. When it warms up I will be dropping my timing more to see what happens. The problem up here in the northeast my rail pressure drop a bunch if its under 34 degree's. The rail pressure dropping in cold weather might be hurting me as well. Smarty is aware of my rail pressure issue and is looking into it.
 
Its your injectors. Also 03 trucks have always had low rail pressure when it gets cold.
 
I am sure the 285 dura's are not helping your mileage either. I run the same tire. Gearing is nice but they are a wide/heavy tire. I had 19.5 tire/rime before putting the Dura 285s on and the tall skinny 19.5's weighed about the same but rolled much different and were great mileage tires. I like the Dura's for the ride and better traction that the 19'5s provided.

Like Dangerous06 states.. Mileage needs to have timing increased so lowering timing to help your smoke control is going to hurt mpg.

I have been increasing my timing in the 1400-2200 rpm/ 12.6-31.3 load range to help my cruising load/rpm.. Have lowered that same rpm range in the 31.3-56.3 load ranges to try and help spool up when getting on throttle from cruising..

Still cannot get the smoke completely gone but am happy how it is going. The never ending quest for unlimited power whenever I want it without causing it to get dark clouds.
Would love to have no smoke but do not think it is possible on the pre 2006 year trucks until we can have all tables like EFI can provide.

I am similar to your truck for fueling and injectors. Arson3 with BB1's. But the 2004.5 does not have the same rail pressure drop like you have with the 2003. My saving grace at the moment is running the stock over the S478. The stocker is helping me control the smoke in the low load areas but is my bottleneck/drive pressure when I turn up the fuel. My goal is to have a small BB Garret with a gate for the secondary in hopes I can achieve happy low end spool/smoke control and mileage. An then use the upper range to fuel heavy enough to keep the primary pushing hard and not cause to much DP.

Good luck with getting the mpg back.. I am having at least some success improving mine at the moment. Still not where I was with stock injectors but getting there.
 
I have been running higher timing then most for 03's in the cruise range and didn't gain anything. I have no issue with smoke at all. The truck runs great just missing mileage. I have s hard time believing it's my injectors since I just replaced them. Other then BB1 injectors I wouldn't run anything else then Don M. I personally think something in the drivetrain is binding and that is causing higher engine loads while cruising.
 
Do you have stock tires to put on as a test? I am assuming you corrected for the tire height going to the 285s. I know the injectors cost me some mileage from the fun factor accelerating. I have to try hard to not speed away from every stop.

Sent from my MB886 using Tapatalk
 
Yes speedo is calibrated. If you go by what nitto wants you to use your speedo will be way off.
 
cj42 said:
I have been running higher timing then most for 03's in the cruise range and didn't gain anything. I have no issue with smoke at all. The truck runs great just missing mileage. I have s hard time believing it's my injectors since I just replaced them. Other then BB1 injectors I wouldn't run anything else then Don M. I personally think something in the drivetrain is binding and that is causing higher engine loads while cruising.
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The injectors are not bad they just dump more fuel than stock.
 
At one time I had Don M. 3.3's and still had just as good of mileage as my 50's and 90's and all were better than stock. Only looses mileage if getting on it. I average about 17 commuting 80 miles a day in heavy stop and go traffic. I can get 20+ cruising if I keep the speed under 70. Any faster it drops pretty quick.
 
I'd be willing to bet you are losing 1.5-2.0 on those 285's alone. My old truck lost that much when I went from stock size to them. That may be only half your lose, but still a considerable amount. $.02
 
I am on 315's with 373 gears. I lost a bit going to the 315's but feel i gained it back with the free spin conversion. Have you checked your alignment, it being out of wack can cause a lot of drag?
 
dangerous06 said:
The injectors are not bad they just dump more fuel than stock.
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There are to many guys I have talked and been in their trucks running 90 - 120 hp injector and are not losing mpg because of injectors especially if you are programming.
 
I thought you did, don't know why so many folk are hung up on them being the issue.

notice anything else? are egt's up? when is the last time you cleaned the air filter?

Did ya back over something and bend your exhaust pipe?

boost leaks checked?
 
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mikmaze said:
I thought you did, don't know why so many folk are hung up on them being the issue.

notice anything else? are egt's up? when is the last time you cleaned the air filter?

Did ya back over something and bend your exhaust pipe?

boost leaks checked?
Click to expand...

My timing almost looks like an 06 in the cruise area. So since my timing is pretty high my egt's from 1400-2000 week be between 600-700 range and boost will be in 4-6 pound range.
I haven't checked for boost leak but I can maintain boost. It doesn't fall off while cruising. When it warms up we will be checking intercooler for leaks. I'm wondering if something in the transmission might be to tight or something binding a little. My rear end is clunking a little when backing off and then getting on the throttle. If this was my daily driver I would be worried more but my diesel Passat save me a bunch on fuel. I love this truck just trying to get my mileage back up. Power is awesome, no smoke and nice riding truck on the back roads.:)
 
Is your truck 4x4?

If so, for comparison, I have a 2003 4x4 with Flux 2 injectors, BB compounds, 285 AT tires, and 3.73 gears. I also have Dynatrac hubs. I DD with a UDC tune based off of TNT #9 that yielded 685 rwHP. Mixed driving with interstate @ 75 mph I average 16 mpg +/- 0.5 mpg. Mixed driving @ 70 mph I average 17 mpg +/- 0.5 mpg.

When I looked back in my fuel records my stock injectors yielded similar mileage.
 
Yes my truck is 4x4. Since the day I picked iy up at the dealer I have never gotten worse then 18 mpg. It didn't matter if I was driving around town, highway or beating on it. I always filled and then drove to my fuel light came on or almost at E. I would see 550 - 620 a tank all the time. Now fuel light will be on at 480- 490. Having said all that I'm sure part of my loss is re-calibrating my speedo. If I remember right my speed was about 1-2 mph off. Showing 72mph when going 70 mph. Now I am about 1/2 mph off so I expected a drop just not this much. I figured when I was done with mod's and programming 17mpg would be when I was done. I was thinking programming and a tighter tq converter my mileage would go up a little and the tire would bring it back down. Just looking for things to check. Alignment may help a little because I know that is a little off just driving.
 
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