unnoticedtrails

EDITED FOR CLARITY:
Hi everyone. I am not happy with my current MPG on the '06 V6 Auto. Ever since I got the dual exhaust on, it has been down hill from there.

My OLD '07 V6 Whinnie *Totaled in April* had a SCT X3 tune with Steeda CAI and nearly identical dual exhaust Flowmaster mufflers with resonators averaged 18-19 MPG in the summer.

But, my replacement '06 V6 Auto only has a drop in K&N and dual exhaust Flowmaster mufflers with resonators.

My car ('06 V6 Auto) is averaging 16.8-17.3 MPG even with some highway. But, the heat has gotten higher in the past week.

What should I do? Go to the dealer? Or ask American Muscle to get my old programmer reprogrammed for $150?


My friend says he had his Ford dealer re-tune the computer in his Mustang for our Colorado high altitude and he got his car running better for $100.

Thank you!

Paris MkVI

Good heavens, I am doing that mileage - and better - with my 4.6. I would suspect there may be an issue lurking somewhere.

Keep in mind, though - whenever we begin to re-breathe the engine, with CAI'a, etc. - more air means more fuel.

unnoticedtrails

Yeah, I don't have a CAI though. So maybe it is the exhaust alone. Hm..

Joeywhat

Make sure air intake is good and clear, no obstructions, clogged filter, dirty MAF, etc. Make sure plugs are good, plug wires and coils, etc.

Rjaniz

What was your MPG before the dual exhaust?

From my experience, sometimes the S197 V6s just suck [fuel]. My 08 V6 wouldn't do more than 18MPG no matter what unless on lonnnnng stretches of highway, then I was "treated" to 24MPG. Even after I dropped in a CAI and a tune, there was still no improvement.

It was one of the reasons I traded it in for a V8. Figured if I'm paying V8 gas bills, why not? (though that proved to be false as my V8 gets anywhere from 21 to 28MPG. Love this car.)

unnoticedtrails

Thanks! I'll look into it! How can I tell if my MAF sensor is dirty? The plug wires, can I visually tell if they are bad? Thanks!

Joeywhat

Do a visual inspection. With plug wires any cracks are an obvious issue, you can also run the engine in darkness and if you can see any electrical arcs from the plug wires then they are bad. If the plugs and wires are old then there is a good chance they are bad. Also look for corrosion at the plug boots. Plug gaps also should be checked.

Basically, do a tune up. Make sure everything is in proper working condition.

unnoticedtrails

Before the exhaust, I saw 18-22 MPG. But, the environmental temps were cooler.

I agree on the fact the 4.0 V6 just sucks. I do kind of wish I got the GT when I looked for a replacement car.

My '07 V6 got better mileage this is one though, I don't get it. I just don't want regrets, you know? I love the exhaust sound. But, with the mileage I seem to be getting, it is really disappointing.

unnoticedtrails

Thank you Joey! I will look tomorrow. I had the car looked over by a shop right before I purchased it from craigslist. But, that was April 15 or so. Maybe they are beginning to fail. Thanks again, I'm a car enthusiast, but not as mechanically inclined as most. I appreciate it.

Joeywhat

They may not have done a very thorough check of everything. That would likely be fairly expensive.

The major components to check are air intake, ignition, fuel and exhaust. It's unlikely the change you did is the cause of your issue. A clogged cat, however, can do that.

If you have a tuning device, hook it up and do some live data logging to check air fuel ratios and if there are any engine codes. You could be running rich for any variety of reasons (which may not cause the engine light to come on).

Also make sure there are no external fuel leaks. An unlikely but possible cause is a corroded fuel line leaking.

unnoticedtrails

Ok, sweet. Yeah, they might have not looked at the plugs. I have an SCT X3 tuner. But, it is from my old Mustang V6. I wonder if it would be worth taking my car to my local trusted shop to look at it. Can a shop make tuning changes to make my car run leaner?

Joeywhat

Maybe. Connect you X3 and go for a drive. If you're able, do an actual datalog and record the info. If not, just pay attention to the air/fuel ratio, and also check for codes. If you are running rich then that could be the cause. The car should run at stoich (14.7:1) when cruising, it will typically deviate a bit when under full throttle and when coasting. If it's real far off, especially while coasting or cruising, that is indicative of a problem.

I would check for issues yourself first. Diagnosing a problem like this can get expensive quick when a shop does it.

Joeywhat

Also, as far as a shop doing any ECU tuning, it's likely they won't. That requires a full on tune (just like if you had Steeda or some other company do a tune for you). It's also unlikely a tuning issue, it is most likely a mechanical issue.

unnoticedtrails

Ok cool, thanks! Yeah. I want to avoid costs if possible. Is there a danger in plugging in the SCTX3 tuner even if it is for my other (now totaled) car?

Joeywhat

No. You should be able to datalog and check codes on any OBDII vehicle.

unnoticedtrails

Ok, but I can't upload a tune to the car with it right?

Joeywhat

Correct, to do that you would need to unmarried the tuner from the previous vehicle and used the new tune to the new vehicle. You can datalog and check codes on any vehicle even if you've already used the tuner to tune another vehicle.

unnoticedtrails

Awesome! You have been a big help Joey thank you!

akdoggie

A large part of the drop in fuel mileage on our 4.0 engines may be caused by a dirty throttle body and/or MAF sensor. The air won't flow correctly, thus the drop in MPG. Remove the TB unit and clean the inside as well as the MAF sensor. Use a good cleaner, designed for MAF cleaning, or you may regret it. Other products tend to give odd reading to the computer and really mess with fuel mileage. I'll suggest using CRC brand cleaner. You will most likely find. inside the TB black as the sidewall of a tire. There are some very small air ports inside, that tend to clog up and will cause the MPG to drop significantly. Once cleaned, reinstall and test it out. You should find an increase in power and the fuel mileage will reappear on it's own. Good luck.

unnoticedtrails

Thanks! I'll check that out. But, in the meantime, I have found what seems to be contributing to it.

I randomly opened the hood last weekend and noticed that coolant had gushed out of the top of the overflow container underneath the cap. It had apparently splashed all over the inner fender wells and shock towers at some point. I opened the tank and it was nearly bone dry. I filled it up and after a few driving cycles, it seems to be ok and not leaking out anymore. (Most likely our oil change place didn't get the cap on tight when they "topped it off". I have seen my mileage creep back up to more "respectable" numbers (taking into account driving habits, location, and outside temperature). After researching it, I saw that low coolant can throw of the MAF and the throttle positioning sensors.