Yotehunter59

Hey guys, I have had my current 1997 CTD/4WD 2500 for about 6 months. My problem is I am new to the maintenance and performance increases of diesels. I did have a 1996 for awhile and it would get what I thought was not great milage in town (15-16 mpg), but it got great milage on the highway (unloaded, 24-25 mpg). It was the exact same model truck, as my 1997 (4WD 2500). My 1997 truck only gets 10-12 mpg city/12-13 mpg highway. I purchased this truck from someone who I think did not know how to tweak the performance the right way. The truck supposedly has a different set of injectors (Edge stage 2) along with a different TORQUE PLATE (unknown which one), and a new Holset housing with Edge Jammer innards in the turbo. I do not know for a fact that this was done, but was shown a receipt for parts and labor. I have been going over the forums for the last 2 days, reading what everyone has to say. I am throwing this out to get honest opinions as to what I can do to bring my milage up. When I leave a light w/heavy throttle, Lots of BLACK SMOKE, and the smoke will follow until I back of the throttle when-ever. On the freeway, if I have to accelerate to pass, again, lots of black smoke. Acceleration is not that great (about the same as my 96), from the start, but at about 70-75 mph, the power really starts to crank up. I can go from 70 to 100 mph real quick. It makes no difference as to how I use the throttle/acceleration, my milage does not change. Off-road, the truck will go forever on a gallon of fuel. I have a 4 inch straight pipe, no muffler, but had to replace the CAT to comply with emissions here in Vegas, EGT gauge set to 1200* but not sure of how high I can set the warning. I can exceed 1200* real easy under hard acceleration or uphill even running without a load. Anyone have any suggestions as to a cure? Thanks in advance....JOHN

xtoyz17

What maintenance has been done? Make sure there are no fuel leaks. Make sure your replacing the fuel filter every 15-20k miles. Make sure tire pressure is up to snuff. Tranny fluid changes? Adjust the bands. Last but not least change the fluid in the axles. Regular oil change intervals won't help mileage but are good, and finally you should consider an additive such as Power Service. Power Service has been known to help increase gas mileage.

Hope it helps, it should at least give you somewheres to start.

Shawn

TIMMY22

sounds to me like the previous owner turned up the pump and installed larger injectors to increase horsepower.


more fuel= more power/less economy it's that simple.

waldersha

If you have LOTS of smoke all the time and don't want it, start with the AFC (aneroid fuel control). If there is a different torque plate installed, the tamper screw has already been removed. Chances are the plate is slid forward as well as the AFC housing. If the starwheel inside has also been turned up, that will certainly cause all the things you are talking about. There is also a "smoke screw" on the back that may have been turned in.

There is quite a bit of tuning that you can do just with the AFC that will clear up your smoke and help with mileage. Do a search for AFC adjustments and you should be able to find what you need. If you need help, PM or post back and we'll help you get it under control.

Yotehunter59

I am not new to "VEHICLE MAINTENANCE", and all this has been done. The major stuff is what I was referring to. I have to do the KDP, or at least check it out. The AFC may have been changed around and this is what it sounds to me as being the problem. I am still studying the causes on this website. This site has been giving me the little details on things that the repair manuals do not. I am after opinions from those that may have had the same symptoms or problems. The previous owner had said he put in a new TORQUE PLATE, but again, before I tear it apart, I am looking for info from those same people that I have mentioned....JOHN

Yotehunter59

Ya, I am sure he did change the injectors for more horse power, but the problem is I do not have the horse power, just lots of smoke. The easiest way for me to sum this up would be to say, he has screwed it up by not doing it correctly and I am not sure what the setting were as stock. I have seen the diagrams on the different plate shapes and understand the directions on the STARWHEEL (which way to turn for more fuel and less fuel)....Thanks, JOHN

Yotehunter59

Waldersha, thanks for the reply. This is where I am thinking the problem is originating. I have even changed from the tire size that the kid who owned this thing before me had on it. I went to the same tire size I had on my '96 4x4. Both of the trucks have the same gearing and I put 285 75R16's on this one, he had 315' on it. Milage never changed, but I am sure that the Tranny will thank me.

Tell me more about he smoke screw and how it is adjusted. I will try to set the AFC housing, ( the tamper screw still has a HEX-HEAD on it, but the kids dad owned a car dealership and may have put a stock on back in), plate and smoke screw this weekend, but am in the process of doing an in-tank fuel pump in a 94 GMC Jimmy first. Thanks,....JOHN