MPG Substantially lowered

[edpapaj13]

I'm wondering if anyone know ways to improve gas mileage? I filled my I30 with 10 gallons and for mostly city driving I was barely able to get 140 miles and not driving with a heavy foot. Im not expecting to get 21mpg but I noticed the past couple years that even highway driving with a full tank I got nearly 300 miles.

[rxm6]

1) Disable your knock sensor2) Replace your y-pipe3) Run full synthetic oil if possible

I'm running approximately 28 mpg currently on my '98 I30 after completing the above steps plus a few other things. And step 2 seems to be the biggest offender. After replacing my y-pipe my mileage shot up from 23 mpg to 28 mpg. Those pre-cats get clogged pretty bad after 10 years and really force the engine to work hard to make up for the loss of power.

[edpapaj13]

I'm not sure about the disabling the knock sensor since 'm afraid i'm going to have problems starting the car again. However number 2 and 3 can be done. How much would a Y pipe run install plus part and can this be done anywhere? (pep boys/meinike etc)

[Wolvrin704]

Might want to do a tune up.

[edpapaj13]

Thats true. The only thing regarding tune up that i've done in my 110K miles of owning the car are brakes/oil change and spark plugs and one time transmission flush. I think I needed to do more than that

[93HATCH240]

[QUOTE=rxm6]1) Disable your knock sensorQUOTE]Wouldn't disabling the knock sensor cause the check engine light to go off? I realize the benefit of disabling it would be better gas mileage but is there any that could go wrong from disabling the knock sensor? Any cons of doing this?

[rxm6]

1) Disable your knock sensor

Wouldn't disabling the knock sensor cause the check engine light to go off? I realize the benefit of disabling it would be better gas mileage but is there any that could go wrong from disabling the knock sensor? Any cons of doing this?

Disabling the knock sensor may be the wrong choice of words. Fooling the knock sensor might be more appropriate. And no the knock sensor does not trigger SES light nor will it even if it fails.

The only cons to disabling the knock sensor are if you fill up with 89 or lower octane. In fact I'm pretty sure the only reason the knock sensor is on these engines is for people who don't want to run premium because they think there is no difference. (Trust me, I know some of these people)

[rxm6]

I'm not sure about the disabling the knock sensor since 'm afraid i'm going to have problems starting the car again. However number 2 and 3 can be done. How much would a Y pipe run install plus part and can this be done anywhere? (pep boys/meinike etc)

Disabling the knock sensor will not give you problems starting the car.

Changing out the y-pipe might be a bit tricky considering its illegal and some shops won't do it. The factory y-pipes have pre-cats for people who decide to start their car and drive it immediately to the smog station. An aftermarket y-pipe will have no pre-cats giving you a boost in power and allowing the engine to work less for better gas mileage.

[MinisterofDOOM]

Personally, I would look into fixing what's wrong with the car before I started disabling sensors that exist for a reason.Even if disabling the knock sensor does fix your fuel milage issues, it is not the cause--which means there's something else wrong that's just getting ignored.

[93HATCH240]

Would it be safe to disable the knock sensor in an 02 max. I run nothing but 93 octane.

[edpapaj13]

Thats exactly what I was thinking. The sensor is there for a reason and disabling it might cause something else not to work right. I'm looking to change my ypipe. I found a warpspeed Ypipe. I think it will improve my mileage better then playing around with the sensor. Will replacing a Ypipe give me any problems regarding emmisions?? Also I asked a shop and they said like 970 for the part and labor. Part is near 750. The one I found on ebay is only 200 doll?? Why such a big difference? Am i looking at the wrong Ypipe on ebay? Here's the link in case someone has time to look at it.

http://cgi.ebay.com/ebaymotors...&rd=1

[NewfoundlandDude]

Call Lynn @ Warpspeed 1-866-801-9338They'll get it to you for $200 + Tax shipped in the states or an extra $35 to Canada.

The install should take no more than an hour or 2.The only problem you might run into are the O2 sensors not wanting to come out. Someone had crappy bolts stuck into my header and they all snapped off. Yours should have studs with nuts.

Spray everything (Front & Back header studs + O2 Sensors + Cat Bolts) with a penetrant and let it sit for as long as is convieniently possible. The penetrant will smoke if you drive around after spraying everything.

They may have a bit of a delay in shipping as one guy pretty much does most of the fab work. It would be good to call and ask before bidding on ebay then finding out that you have to wait for more to be made.

[edpapaj13]

Thanks for the instruction however I am thinking of taking it to a proffesional and pay for installation. I'm not sure though they only have one person making the Warpspeed ypipes?

[NewfoundlandDude]

I'm sure that they have more than just Dallas on staff, but I have heard stories of them being slow with shipping & such due to supply.

You could also try Budget Exhaust (LSS Exhaust) out of Toronto, Canada.

[rxm6]

I'm sure that they have more than just Dallas on staff, but I have heard stories of them being slow with shipping & such due to supply.

You could also try Budget Exhaust (LSS Exhaust) out of Toronto, Canada.

Budget is fantastic. They have real quality in their work.

For the best results, heat wrap your y-pipe.

[Sentientbydesign]

I'm not guarantying that this will work, but you might clean out your MAF, IACV, Throttle body, and intake manifold.

When I cleaned out my IACV, I noticed a small handful of "carbon" deposits pour out of it. I'd say about and eighth of a cup. It was kind of weird.

Check your spark plugs, tire pressure, alignment.

[edpapaj13]

I know my alignment is messed up. Its' been for 2 years. It leans like an inch or more to the left. I have to hold the steering wheel with my right hand that much down for the car to go straight but I doubt it had that much affect on the mpg. I can check the tire pressure and alignment. The other stuff you mentioned Id have to let my friends do it cause I never went near any of them and don't really know where they are. Does Ypipe by itsself really add any HP or is that just to advertise it? and also anyone with Maxima/I30 with 140K+ what mpg are you guys getting?

[Sentientbydesign]

Your alignment makes a HUGE difference on your MGPs. Think abou this. If your tires are all going straight, there is very little drag put on the engine, the moment your to or caster change, the car is going to start pulling and dragging your tires.

I'd get the $60 alignment and save yourself money on gas and tires.

And IMHO, unless you plan on restoring your car, don't add performance parts to it. You'll only make it clunk sooner.

The IACV and Throttle body are quite easy to clean. You can find tutorials for both on the FAQ area of this forum and on http://www.motorvate.ca

As long as you don't snap something because of carelessness, you shouldn't have a problem with doing either.

The intake manifold is a little more difficult.

Have you cleaned your fuel injectors?

[rxm6]

...Does Ypipe by itsself really add any HP or is that just to advertise it?

It releases HP that the engine already possesses but can't use due to restrictions. Furthermore, a y-pipe with a stock exhaust setup is hardly noticeable.

...and also anyone with Maxima/I30 with 140K+ what mpg are you guys getting?

28 mpg.

[edpapaj13]

I'm not looking to restore my car however I thought if I can, I should add some performance parts to my car, basis additions. Im getting a cold air intake and I figured with the Ypipe I'd get some more HP on it. If I my mpg improves that I'm putting the Ypipe on hold.

But no I Haven't cleaned my fuel injectors. We have a maxima meeting this sunday and I will take my car. Other members can show me how to do all that stuff.

I guess so far I should do all these easy stuff that you guys mentioned like alignment, clean MAF, IACV, Throttle body, and intake manifold, fuel injectors and record the mileage. If it gets decent mpg near the 20' then I won't install the Ypipe.

[edpapaj13]

I just did my alignment today, got the tires rotated, however now my car leans a little to the left. I will drive it some more and see maybe its just me. Also when I freaked out about the 14-16 mpg i didnt let the gas go too low. When I counted it the needle was on Empty but the low fuel light didn't even come up so I guess I had some 20 or so miles in it. I think I still need to get better than 18-19mpg on my car so I will do what you guys recommended this weekend

[Sentientbydesign]

When you say it "leans a little to the left" do you mean the whole car when looking at it from the rear leans like a person does or that it pulls to the left when you're driving it? If it's pulling, then I'd take it back to the alignment shop and have them correct it.

If the actual car leans, then you might have bad springs, bushings or struts.

The only "accurate" way to estimate your mileage is to fill up your tank and reset your trip odometer. Then on your next trip to the station, fill up again. Take the number of miles on your trip odometer and divide it by the number of gallons you just filled your tank with.

Our tanks are supposed to hold 18.5 gallons. I've gotten 17.6 in from a "completely empty" tank. I drove until my car stalled over and over...

I get about 18 in the city and 21 mixed. If I'm really careful about when I brake and how I accelerate, I can get 24 on the hwy.

[edpapaj13]

Not leans, pulls a little to the left. Like less than half an inch to the left. I have to hold the steering wheel to go straight. Its better than I had but I don't know if I should take it back cause it seems minor. That what I did but the problem is that I don't want to drive the car until I get stuck somewhere. I fill it for 10 gallons usually and when it goes near Empty I see the mileage. I still keep seeing 15-16 mpg city but i've been braking hard cause I had to avoid 2 accidents in 2 days from stupid people turning on red and covering two lanes or decided to turn when i'm 15-20 feet away from them. I wish I could lock them up.I guess its not that bad if i'm only a couple mpgs away. Since I had my alignment done and if I clean my MAF, IACV, Throttle body, and intake manifold I can see more improvement. If I reach 18-20 then i won't buy the Ypipe.

[Ryan Heo]

Hi.I have the same problem. My I30 is also 15~16 miles per gal in the town.It is painful. I don't know why at all. I've been in New York on middle of Aug. At that time, the car was driven to 420 miles per 16gal. on the highway. It is almost 27 miles per gal. After that, it extremly drop the gas mile from 420 miles ot 330 miles on the highway.

[edpapaj13]

Check the beginning of the forum, I got a lot of great ideas in responses. First thing I did was get my alignment done, I recorded my mpg to 17mpg from 15-16 previously in the city. I'm really hesitant to get the Ypipe if by cleaning MAF, IACV, Throttle body I get near 19mpg city.

[Sentientbydesign]

Take the car back to them and tell them it's not tracking straight.

They'll do a test drive and they need to fix it again until it's right.

I have a lifetime alignment on my car and I keep taking it back, but in my case, all of the bushings except the LCAs are 270k miles old.

I think, I'd need to have the frame straightened, a new rear axle, and all of the bushings replaced on the front end in order to track straight.

I'm also getting horrible gas mileage right now. Like 16-17 mpg in the city. That's down from about 18-19 that I was getting a couple of months ago.

I'm going to open up the intake manifold pretty soon to clean it and I'll let people know if that helped at all.

[bluegen1e]

you guys think thats bad. i get about 270miles city and about 300 hwy. and that's me being generous. where do I begin?? i'm a newbie with some basic knowledge. whats IACV?

anything i can do to improve other than the ones mentioned here? cos my **** is straight dodge ram status...

[Sentientbydesign]

IACV, it's the Idle Air Control Valve.

It's attached to the throttle body (right above and behind it).

Clean out your throttle body by loosening the hose clamp attached to it and pull the intake away from it, then get some throttle cleaner and have at it.

You might also want to get a tune up if you haven't had one in a while. I can't justify it on my care because it has WAY to many miles on it and I doubt there would be much benefit.

[Ryan Heo]

I've live in Michigan. Here comes already in winter.So my I30 is always driving with heater. It makes horrible gas mileage.I'm sure that I'm driving the same distance, route, and time.The car is always feeding premium gas(oct 93) on the Shell.Between May to September : 15~16 miles per gal.Now : 12~13 miles per gal with heater.

I guess my engine is getting bigger 3.0 V6 to 5.8 V12....Of coure the same horse power and torque...

Thanks.

[Beancooker]

Your alignment makes a HUGE difference on your MGPs. Think abou this. If your tires are all going straight, there is very little drag put on the engine, the moment your to or caster change, the car is going to start pulling and dragging your tires.

I'd get the $60 alignment and save yourself money on gas and tires.

Agreed 154867%.

If your car is 1º out of alignment, for every mile you drive forward, you are dragging the tires 600feet sideways. Think about how much energy it will take to drag them sideways, as well as the unnecessary wear on the tires.