Loss Of Fuel Mileage! I Need Help!

99RANGER-70STANG · 05-07-2008, 03:24 PM

I need help real bad! I have a 99 Ranger, 4.0 V6. I have a Gibson exaust system, K&N cold air intake, 4:56 rear gears, a computer Jet Chip and it's lifted with 33'' mudders. Before I did all of this work to this truck, it was bone stock, getting about 225 miles to a full 18 gallon tank. After doing all of this work 2 years ago, I was getting 220 miles to a full 18 gallon tank. For the past 6 months, I've seen the fuel mileage go down drastically from 220, to 200, to 180, to 140 miles to a full tank without changing anything mechanically.

By using a combination of my own judgement and other peoples comments and suggestions; I've replaced the following parts in hopes to increase my fuel mileage:

-FUEL PUMP
-FUEL PUMP RELAY
-2 O2 SENSORS (CLOSEST TO THE EXHAUST MANIFOLDS)
-MASS AIR FLOW SENSOR
-SPARK PLUGS
-SPARK PLUG WIRES
-FUEL INJECTORS

After replacing all of the fuel injectors and all of the spark plugs because a couple of them were flooded from the bad fuel injection, my fuel mileage jumped up to 200 miles to a full 18 gallon tank. To me, it just doesn't seem enough!

Can anybody help me to figure out what else it could be? It's also pulsating a little when sitting in nuetral or at a light.

Do I need to disconnect the battery to reset the computer after replacing fuel injectors? Could it need engine work?

Thank you in advance. I am completely out of ideas on my own!

-Todd
(858)568-5032

naturallysmashed · 05-08-2008, 09:19 AM

clean the egr and throttle body.. definitely helped me save gas.

davidw · 05-08-2008, 10:04 AM

well, my only thought is that the huge lift and tires are making your truck work alot harder than it normally would, maybe causing normal fuel decresion happen sooner than it normally would. maybe clean and keep it tuned up anually.

99RANGER-70STANG · 05-08-2008, 12:50 PM

davidw,

Thank you for the response. The thing is that before I did all of the work on the truck, it got 225 miles to a full tank. After doing all of the work, with the combination of the cold air intake, exhaust chip and 4:56 gears, it got 220 miles to a full tank (a 5 miles less). Only in the last 6 months have I noticed it drop from 220 gradually to 140. Then after the new fuel injectors, it jumped up to 200 miles to a full tank. Something else isn't right.

99RANGER-70STANG · 05-08-2008, 12:52 PM

naturallysmashed,

Thank you for your response, as well. I've cleaned the throttle body many times and I didn't see a difference. Although, I have not cleaned the EGR. That might help. Do you know how to tell if your EGR is bad?

davidw · 05-09-2008, 10:12 AM

what did the exhaust chip do for you? does it give you better mpg and power at all? how much $?
also, the only other thing i could possibly think of is that maybe your losing compressing in your cylinders, making the truck work harder to move, = less mpg. and getting the new injectors helped, but only in the fact you were improving fuel flow into the cylinders through the injectors. that s why you jumped back to 200 miles in a full tank. i had a toyota that had only 66% compression left in the cylinders, = less power, worked harder to move the truck itself. but im not sure on all this, just a thought i guess....

Hankster · 05-10-2008, 09:54 PM

You've already dumped a TON of money into it with mixed results.....spend a few WISE dollars....get a PROFESSIONAL diagnostic run. Then you'll know for sure! Problem with asking here is....you have so much non-factory stuff (custom) parts on there....hard to know HOW that stuff is interacting with the rest..with doing a diagnostic run.

99RANGER-70STANG · 05-11-2008, 01:33 PM

Thank you davidw.

Well, to tell you the truth; the only think I REALLY noticed is that the chip helped the transmission shift faster. Since I last replied, I did yet another once over on the truck. I did the "Sea Foam trick" and really worked hard on cleaning the throttle body. I also took the chip out. Since then, I haven't driven the truck enough to notice the MPG difference but I have noticed a great deal in power (Get up and go!) difference. My intake and throttle body whistles now. Just like it did when I first built the truck up. I'm thinking about putting the chip back in to see if there's even MORE of a difference in power. Considering, I spent just about $250 bucks on the thing! I'd like to get my money's worth. I have a feeling that the thorough throttle body cleaning did the trick this time!

davidw; do you know a good "home remedy" to do a good compression test?

Thank you Hankster;

Well, since this all started, I've taken the truck to 2 different shops spending over $200 Additional dollars on just diagnostic tests. They found nothing! I'm going to see how the throttle body cleaing effects it and get back to you all then. I'm also going to install an electric fan and put a bed cover on and see what happens. What is your take on a throttle body spacer? Also, what do you think headers would do for the fuel mileage? Thank you all for your help and I hope for MY sake and my WALLETS sake, I don't have to ask you guys anymore questions! Take care.

davidw · 05-11-2008, 01:36 PM

no i actually don't know how to get a good compression test at home.... i took it in

naturallysmashed · 05-12-2008, 02:50 PM

the cel would come on or the spring wont move around.. honestly this is the only thing i KNOW ive gained better gas mileage from.. its simple.. take it off (2 bolts) spray the crap out of it with any cleaner.. let it sit for a minute, dump it out.. and repeat if you need to.. mine was so clogged i had to take a drill bit and push the crap around into my intake manifold lol.. i probably get another 25-35 miles per tank now.