2007 Infiniti M35X (Gas related issues) SERIOUS PROBLEM

[Infinitigirl14]

Hello everyone,

I really need all the help I can get. I have 2007 Infinit m35x and she is sucking up extremely to much gas. Now, I'm saying this as a cheap person but because i fear there may be an under lining issue and that concerns me. Ok, from the begin inning..... My car has 71,000 miles, I got it at 61,000 miles. I haven't done any mechanical work besides brakes and of course regular oil change. (Keep In mind in a female and oblivious to car maintenance) none the less I do pay attention to my car. One day leaving the bank a mechanic (although he claims to be) said I was leaking something, in reference to my Egr. I had started putting regular gas in my car months ago. So he said that clogged my Egr and he went on to release the fumes from under my hood. Afterwards, he told me run out the rest of my regular gas and start putting premium back and add some Lucas feel injector. I did just as I was told..... Now, he stated that I wouldn't have issues of burning gas and to much hesitation going up hills. However, I feel a slight hesitation when I accelerate, I wat h the window with RPm needle jump and everytime it does my car hesitates. So, I hope I haven't lost tall yet but I'm really trying to give all the details. Now, im using premium and super gas which ever is closest when I'm in need of gas. Now I'm aware this car doesn't get great car mileage but sheesssssh. I put $40 in for super gas and it gave me 263 miles and in one day of driving I was down to 139 I'm so confused because that's just to much gas being burned. Idk if I need a gas filter or tune up or what!! Idk if the Egr is bad or if I should use only premium gas or regular. I'm so lost, but I don't want to go to the shop and they charge me an arm and a leg for the wrong issue!! Please anyone help me! I love this site and yall always give go advice on Infiniti and Nissan. REMEMBER THAT MY ISSUE ISNT BEING CHEAP but that I believe something else maybe going on under the hood. Please share your stories and elaborate with details!!! Thank you so much

[svard75]

First of all our engines don't have an EGR valve. They perform valve overlap which performs similar function but internally. Your sure the mechanic said EGR valve?
You have the 07 so your engine is still the VQ35DE which absolutely can use regular gas.
How many miles do you get on one full tank of gas?

[Infinitigirl14]

Yea that's what the man said, and he said it was a hug price Japanese car so it was recommended to premium gas in it or else the regular gas would cause me to blow out my engine. i haven't paid attention to how may miles I get with a full tank I've just started to notice how much gas is being used and so quickly.

[svard75]

Lol find another mechanic. Our vq35de engines run fine on regular gas.

[Larz]

I am not aware of any HUGE trouble if you use less than 93 octane fuel. Your car's status display will show you "miles to empty' as well as "avge MPG". That should allow you to tell what you're getting in gas mileage.
ALSO: when you fill-up, the fuel handle will shut itself off after the tank has about 19 gallons (it does not fill the tank to the top). so just multiply your "avge mpg" x 19 to see what you can expect to get on a full tank (that's just an estimate, of course).

Just as a reference, my 07 M35 RWD got about 16 in day-to-day driving with 93 octane fuel and close to 24 hwy mpg. I read somewhere that mpg is also reduced by lower octane fuel, but I can't confirm that.

Another thing to remember: Engines get less mpg in winter months than in summer months so if you live in the north, you should see a decrease this time of year. I have no clue how big the difference is, but on my treks to the north in winter I noticed a decrease - I just can't remember how much of a decrease.

[Infinitigirl14]

It seems to be dramatically decreasing which just seems odd to me. I brought the car Christmas eve last year and up to now I never witness my gas rapidly decrease like this.... That's why I thought maybe it was a an issue. Let's just say U start the car and it says miles until empty is 133, u go around the corner and is says 115 then u go to the next city over and it say 95... That seems so odd... This is what's happening with my car on Super gas. I filled it up to almost a half of tank on Friday and today it's right below a half tank. So I assume it will be gone by tomorrow night... Could there be a leak anywhere?

[svard75]

How many miles between those points you indicated? Something important that Larz mentioned was your gas pump stops at about 19 gallons. Do you manage to fill that much? It's possible the gas pump auto stops well before it's completely full and for some reason the fuel sensor is not working properly. However that is a far shot.
What I would like to know is if you perform regular maintenance like engine air filter change, oil changes, other fluid changes at that same mechanic, and if he's actually doing anything or simply playing around. you mentioned your car struggles when you're accelerating. Do you know how to remove the engine air filter? Something as simple as a blocked air filter could cause those symptoms, then again it could also be a blocked catalytic converter. Before you panic, I suggest you take your car to a Nissan dealership for diagnosis.

[The00Dustin]

As several people mentioned, regular fuel will not hurt the M35. That having been said, while it isn't true in most engines, yours will have better performance with premium because it has to de-tune itself to run regular.

What is really concerning to me is that no one has responded to this:

However, I feel a slight hesitation when I accelerate, I wat h the window with RPm needle jump and everytime it does my car hesitates.

Unfortunately, I can't really offer any input on it, but it might be helpful to describe which direction the needle is jumping, from which RPM to which RPM and how much hesitation there is (maybe in time?).

Regarding your consumption concern, my 2006 M45 (which does require premium due to the V8) has had a problem with the gas gauge since it was under warranty, but the dealer couldn't find the problem to fix it. When I'm driving along with the gauge somewhere under 1/4 tank, the needle will drop all the way below E and stay there for a short while (maybe a mile or two), then it will come back up to where it was. When it does this, the fuel economy screen will change from whatever miles DTE to 0 miles DTE (and it actually says 0 miles instead of saying ** miles like it normally does once it gets low enough that it won't estimate). You could be seeing something similar to that where it is just a calculation/reading issue.

Additionally, when I fill my tank, say it says I have 380 miles DTE and it showed an average of 21 MPG before fill-up and reset. I can drive 100 miles and have an average of 21 MPG on that 100 miles and it will definitely show a number lower than 280 miles DTE. However, in my experience, the miles DTE number consistently gets further and further from reality (in the negative direction, meaning you could go farther than it says) as the tank gets lower. Additionally, the miles DTE number is based on a recent short portion of your drive, so when you drive around in town, it will drop due to the lower recent mileage, and when you get out on the highway and drive 15+ miles, it will at least stay the same for most of that drive if it doesn't increase.

Given that these numbers are not really consistent and are mostly just for reference, it's probably not worth getting worried over them. However, what you can (and should) do is actually calculate your mileage and compare it with two things:
1) The average mpg in the fuel economy screen (which you should reset each fill-up when you calculate). This will help you determine how accurate your fuel economy screen is (mine will be up to 1 MPG low in the summer and up to 1 MPG high in the winter).
2) Average/expected fuel economies (some people use fuelly, fueleconomy.gov can provide the recalculated window sticker numbers and some average numbers from real world drivers).

To calculate your fuel economy, you should fill up the tank, reset your tripmeter, drive until you're ready to fill up again (over the course of a week or whatever), and then repeat. Each time you fill up, you take the number of miles driven divided by the number of gallons pumped to get your MPG, which you can compare to the resources just mentioned.

You can also use an app to calculate and track this. I recommend acar if you have an android mobile phone (don't know if they make it for iPhone). I think it may even be free if fuel is the only thing you want to track.

Hopefully doing that research/calculation will help you find out that your fuel economy is where it should be and give you one less thing to worry about.

[Ilya]

First off, can a bunch of you members PLEASE update your profiles with locations? No one is gonna come get you, but it could certainly help people help each other. For example, if someone has an issue and another member happens to be close by, perhaps helping member can look at car in person, etc.?

Please update your profiles!

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That being said, you might have a bunch of things going on causing the hesitation:

1) Spark plugs (could lead to misfire)
2) Coil packs (could lead to misfire)
3) Sometimes you just get unlucky with poor quality gas. Try another gas station?
4) Clogged air filter (causing the engine to starve on air and thus not get the right air/fuel mixture needed)

My suggestion is to buy a can of seafoam (from your auto parts store), pour ALL of it into an almost empty gas tank, and fill the car up with 93. As you drive, the seafoam product will go through your fuel system and remove any moisture, etc. in the fuel and 'stabilize' it. Let us know how it runs.

Also, is your check engine light on? Even if it isn't, I would go to advance auto parts or similar store and have them read your ECU (engine computer unit) for any pending error codes (they are in the system, but don't yet trigger the check engine light). This could help point you in the right direction of what you need to focus on.

Again, if you are in upstate NY, I may be able to stop by and take a look for you.

[svard75]

First off, can a bunch of you members PLEASE update your profiles with locations? No one is gonna come get you, but it could certainly help people help each other. For example, if someone has an issue and another member happens to be close by, perhaps helping member can look at car in person, etc.?

Please update your profiles!...

Done

[Ilya]

Thank you Private!

[Larz]

First off, can a bunch of you members PLEASE update your profiles with locations? No one is gonna come get you, but it could certainly help people help each other. For example, if someone has an issue and another member happens to be close by, perhaps helping member can look at car in person, etc.?

Please update your profiles!

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That reminds me ... When last we were came round to do some midnight filming, one of the crew remarked that the white heels your g/f was wearing really didn't 'go' with the lingerie - we suggest "arrest-me-red" stiletto heels next time.
Oh ... one of the bulbs on the security lights might be a little loose, and sorry bout the MacDonalds cheese burger wrappers in the garden. Complete coincidence,it was NOT Scooter! honest!

[Ilya]

...lol.

Let's keep this thread on topic folks. Let's help her fix her car.

[Brian35XR]

...lol.

Let's keep this thread on topic folks. Let's help her fix her car.

Have we confirmed anything is wrong with her car yet? These cars are notoriously horrendous on gas and everyone thinks it's physically something wrong with their car at first when it isn't. My car shows similar behaviors (dropping 10-15 MTE in a 2 mile drive) but that adjusts automatically based on driving habits. If I hop on the highway it goes back up 50+ miles. No matter what the Avg Fuel Economy shows 15.5mpg which is absolutely horrible but hey that's the M35x.

[Ilya]

Some members get around 20, and I myself get 18 with a heavy foot. If she's getting 14-15...there could be a problem. She does state that her car hesitates so...probably an issue.

[svard75]

True. It depends on how often you reset the fuel economy setting. For example I only reset between fill-ups not every day. If I'm stuck in traffic I get 20 or more liters per 100km actually the other day I got up to 65 lol. As you drive longer it gradually comes down then usually settles at around 15.7km/100l.

I think it's more the fact that the mechanic told her the cause is her blocked EGR valve and the hesitation that concerns us most.

[fat3oy]

Hesitation - hmmmm...

If it is jerky - you might have some ping/det issues... ESPECIALLY if the people you bought the car from replaced the stock spark plugs with copper ones - AND have been running regular gas...

If it were my car:
1. Check the spark plugs
2. If not good replace with NGK iridium - stock temp
3. Check intake piping for leaks - just standard stuff there, hesitation in mind.
4. It will be a point of contention - but I would not run regular gas
5. If spark plugs are good (whether by default or you replaced them) seafoam that bish.
6. Once seafoamed - fill tank with premium - disconnect battery overnight - next day granny the car for at least 15minutes making sure to run all the gears.

IF HESITATION IS JERKY
7. Do throttle reset procedure
8. Have a mechanic check fuel pressure
9. Check functionality of fuel pump

LAST
10. CHECK UP STREAM O2 SENSORS! ANY GUM OR JACKED-UPNESS WILL DESTROY YOUR FUEL ECONOMY. Unburnt fuel, or pre-detonated rich environ will cause deposits on the O2 sensors causing all sorts of shenanigans.

Also - I get around 9MPG!!!!