Poor gas mileage

[Azsnake]

I've been getting poor gas mileage. I average about 170-180 miles per tank. Any ideas on how to improve it? I hardly ever take it above 3k rpms, use shell premium gas, tires are inflated properly etc. You'd think I'd be getting better than 170-180 miles per tank!

Any ideas?

 

[99MystiC]

IS the car tuned? When did is start happening? Did you change anything and then it started? Does the exhaust smell like its very rich?

 

[Azsnake]

IS the car tuned? When did is start happening? Did you change anything and then it started? Does the exhaust smell like its very rich?

No tune. It started happening about a month ago or so. The car is 100% stock except for a mac catback. So I haven't changed anything that would cause the drop in mpg. The exhaust does smell a bit rich. Sometimes the idle is a little rough but otherwise the car runs like a top.

 

[MrBrain]

broken O2 sensors usually cause this behaviour..?

 

[Azsnake]

broken O2 sensors usually cause this behaviour..?

I don't have any MIL on? I just passed emissions on Sat too? :shrug:

 

[VirtualSVT]

Do ya'll change to winter fuel out there? I always drop MPG in the winter even in FL.

Also wake that baby up...3K is pathetic..hahahah

 

[fire_4_effect]

perhaps it's time to get a 4-banger.

 

[Azsnake]

Do ya'll change to winter fuel out there? I always drop MPG in the winter even in FL.

Also wake that baby up...3K is pathetic..hahahah

I'm not sure if we do? I'd have to find out. I would bring it above 3k but 95% of the roads I drive are 35-45mph limits haha. I open it up on the freeway though!

No 4 banger for me

 

[Darkc0bra]

If you want decent fuel mileage why do you own a DOHC V8 :beer: Get a 6 cyl then if you dont want a 4 cyl. Why are you against 4 cyl for?

 

[Ande99SVT]

Gents gents gents...he obviously has a problem, as I average 240+ to the tank on my 99 with full exhaust.

Any drops in performance?
Any changes in how the engine has been running in general?
Any funny noises coming from your engine bay?

I just popped an 02 sensor and she has been idling funny with poor mileage, though mine is an easy fix and you just passed emissions...hm...

 

[Azsnake]

If you want decent fuel mileage why do you own a DOHC V8 :beer: Get a 6 cyl then if you dont want a 4 cyl. Why are you against 4 cyl for?

Oh I was kidding about not wanting a 4cyl. I would love to have a 4cy or 6cyl daily driver. I don't mind the gas mileage. I was just comparing it to the gas mileage thread and I just thought mine was a bit low.

 

[Azsnake]

Gents gents gents...he obviously has a problem, as I average 240+ to the tank on my 99 with full exhaust.

Any drops in performance?
Any changes in how the engine has been running in general?
Any funny noises coming from your engine bay?

I just popped an 02 sensor and she has been idling funny with poor mileage, though mine is an easy fix and you just passed emissions...hm...

It has had a bit of a sluggish feel lately but not terrible. No strange noises at all! Maybe injector problem? Or o2? I have no engine lights on. It has 53,000 miles on it.

 

[006]

When I was running the 99 ECU in my car, I would average 150-170 and rarely, up to 180/tank 80% city.

With the 01 ECU, I get 180-240/tank 80% city.

I think that getting a tune will net you 240+/tank

First thing I recommend is cleaning your MAF. It must be super dirty if you've never cleaned it.

How to:

BULLITT Cleaning the MAF Sensor

Good Luck!

Ken

 

[99MystiC]

I was thinking the same thing just get it to a tuner and have him check out the fuel system. The fuel pump cycle and all that stuff.

 

[Azsnake]

Good info guys. What specs should a good tune look like? What should timing and A/F look like for a good custom tune? What percent should the pump be at?

 

[01yellercobra]

If all he has is a catback and this just started recently then I don't think a tune is the answer. Start with the simple things like cleaning the MAF as suggested as well as a tune up. If you can datalog check to see how the O2's are functioning. We get the winter blends out here and it does affect mileage. Don't forget in the colder weather your car takes longer to warm up and that will affect mileage as well.

 

[006]

If all he has is a catback and this just started recently then I don't think a tune is the answer. Start with the simple things like cleaning the MAF as suggested as well as a tune up. If you can datalog check to see how the O2's are functioning. We get the winter blends out here and it does affect mileage. Don't forget in the colder weather your car takes longer to warm up and that will affect mileage as well.

The 99 ECU seems to run super rich from the factory. My buddy whom I did the same motor swap for, gets ~150-160/tank 90% city and all he has is a catback.

Most people with a tune get really good mileage.

If you have a diablo predator tuner, you can get one from this guy:

Tuning Super Store - Custom Tuning for DiabloSport Predator and Trinity

:read:

 

[GTOBobby]

Do ya'll change to winter fuel out there? I always drop MPG in the winter even in FL.

Also wake that baby up...3K is pathetic..hahahah

I'm not sure if we do? I'd have to find out. I would bring it above 3k but 95% of the roads I drive are 35-45mph limits haha. I open it up on the freeway though!

No 4 banger for me

We do change here in AZ. I think the winter fuel mix starts in October, and goes through March or April.
My gas mileage did the same thing. Then I realized I put 4.10's in.:burnout:

 

[slowbra99]

I get about 180 to with 1/4 tank left. I usually fill up before it gets down too much.

 

[Darkc0bra]

Oh I was kidding about not wanting a 4cyl. I would love to have a 4cy or 6cyl daily driver. I don't mind the gas mileage. I was just comparing it to the gas mileage thread and I just thought mine was a bit low.

Ya i know I was messing with ya...kind of :beer: I get about 280 to a tank in mine with minor mods, nothing crazy. I say if your not getting close to 200-240 something is up oke: