Howdy folks.

1995 Maxima GXE Automatic.

I've recently been noticing some strange behaviour from my automatic transmission. I'm not certain if it's something of concern, or if I'm just not yet used to firing on all my cylinders again (spent the last eight months fighting misfire after misfire and had forgotten what it felt like to drive on all 6 cylinders).

1.) Car is idling high at 1000-1100 RPM while stopped or in Park.

2.) Overdrive does not kick in until I hit about 115-120kmh (70-75mph). Is this normal?

3.) Under 115kmh the car cruises at 2600-2700RPM. Is that high? It must be, engine sounds like it's working overtime because it's not shifting into overdrive.

4.) Coming off the highway, decellerating from 115kmh, the car gives a good "jolt" of power with each downshift of the Auto transmission.

Gas mileage has taken a big hit, seemingly as a result of the issues listed above.

Are any/all of the issues above symptoms of any problem(s) in particular?

Any theories or insights?

Thanks in advance for any advice.

 

1) yes that is A LITTLE high. should be around 750. but it might be so high b/c its not fully warmed up yet. my car idles that high too when i first turn on the car. just let it sit there for a little while and see if the RPM drops a bit.

2) no that is not normal. O/D should turn on when ever you want it to. well at least mine does. so yeah you have a problem there.

3) 2600-2700 rpm is not high if youre just cruising. that is about where my car is when i'm cruising.

4) dont know about that one.......never seen or felt that before.

5) how much are you gettin to the gallon? you might have other problems that is causing the bad gas milage. i.e bad ks, dirty TB, need new spark plus

 

-=PK=-Maxima,

Thanks very much for the reply.

I'm getting about 11 miles to a gallon or just over 200 miles to a tank, 98% inner city driving. My economy used to be more in the vicinity of 15 to 16 miles to a gallon or about 280-300 miles to a tank in the city

I just did my plugs a week ago (NGK V-Power Coppers due to budget).

My throttle body was thorougly cleaned 3 weeks ago along with a fuel injection system flush (MotorVac).

As for the knock sensor? That could definitely be it. I've read a lot about bad knock sensors, although my ECU has yet to throw a code for it.

Could timing be an issue? The car doesn't seem to remember anymore when the best times are to shift into the appropriate gears. Could this be the result of my timing chain being off a bit maybe?

Or maybe a sensor problem like the KS as you mentioned, or another sensor (Throttle position, crankshaft position, oxygen.....etc.)?

Thanks in advance to anyone that can offer any advice.

 

i say check all of ur fluids, just to be safe

 

"Low gas mileage can come from any number of places. Let's start with the basics. Keep in mind the following for optimal gas mileage: use 91+ octane fuel, try to keep RPMs below 4k (normal), your car must be in overall good working order (good oil, good coolant etc) and other factors. If you're doing a bunch of 5 minute trips, or its 0 degrees outside, don't expect gas mileage to be so hot. Also keep in mind that different types of gas can have an effect on the mileage. Shop around to find the best gas you can. But if none of these describes your preidcament, read on. Below are some common causes and cures for bad gas mileage.

1) Air filter. The stock filter on the car is a drop in panel filter. If you bought your car used there is a chance that the filter may have never be changed. This would be the time to do it and you have several options: drop in K&N filter, cone filter or CAI. A search on any of these terms will resolve any questions you may have. If you have a cone filter, the filter may be dirty. K&N makes a recharge kit that is available at Pepboys to clean the filter.

2) Fuel filter. The fuel filter is small gray cylinder on the back of the firewall that is to be changed on a 60k service interval. It is often to blame for bad gas mileage, but can be a pain in the butt to change, but it can be done. The filter is relatively cheap from Nissan. Some members reccomend buying a fuel filter for a Nissan 300ZX. Its the same size hoses, but twice the size, so it lasts 2x longer and is doubly effective. The choice is up to you. The writeup to change the filter can be found here: www.maximadriver.com

3) Spark plugs. If you're running anything other than NGK plugs in your engine, or you bought your car used, go get some NGK spark plugs for the dealer. Spark plugs are to be repalced every 60k miles, but rarely are. They will cost about $10 a pop. Sprintmax has a great spark plug changing writeup that can be found here: http://www.sprintmax.com/tails/sparkplug.htm

4) Dirty throttle body. The throttle body is the first piece of metal behind the intake system. It accumulates a certain amount of dirt and grime. Those who clean it out after long neglect find their car is smoother and that fuel economy does increase. Writeup can be found here: www.motorvate.ca

5) Tire Pressure. Stock tire pressure is 29psi. I found recently that mine were at 25 and filled them up and found a substantial increase in fuel economy. If your tires are low, go ahead and fill them up (I filled to about 31, but everyone has a preference).

6) Oxygen sensors. If an oxygen sensor is messed up, it will trigger a Check Engine Light. There are three sensors in total. 2 rest in the respective branches of the Y Pipe (these are the Front Heated 02 Sensors) and one rests in the catalytic converter (95-96) or in the B Pipe right behind the cat (97-99). If any of these sensors fail, gas mileage will decrease substantially. Many sites exist that sell oxygen sensors (dealers will charge a lot). www.buyoxygensensors.com gets good reviews on this site frequently, and they have good prices. For a writeup, go to www.motorvate.ca, or search around the .org

7) Knock Sensor. This is the bad boy, the code everyone fears. The sensor is actually just a piece of metal that rests under your intake manifold. They cost approximately $110 from various sources (www.thepartsbin.com is usually cited as one of the best). The sensor is not terribly difficult to change, but as my friend Harold described it, "Nissan must weld razor blades under the manifold." Due to tight fitting, the sensor often results in a bloody hand. The writeup for the sensor can be found at www.motorvate.ca

8) Dirty fuel system. As a car grows older, carbon deposits in the fuel path, clogging areas such as the injectors. Many modern gasolines are designed to combat this (such as Chevron with Techron) and there are many additives that can be added to gas to clean out these systems. Many mechanics offer a full fuel system clean out for about $50-$75. Many .orgers believe this to be BS, some think the process is valid. The choice is yours.

This is the ticket to good gas mileage! Any other questions can be resolved using the search function, as this subject is discussed quite often. Enjoy!"
credit to gepetto

 

-=PK=-Maxima,

Thanks for that very informative write-up. Much appreciated.

I'm going to investigate further my oxygen sensors or my knock sensor. The reason I say this is because I follow every other rule of thumb you described religiously.

My plugs are brand new (NGK V-Power). I Just changed my fuel and air filters. I just had a my throttle body cleaned as well as a clean and flush of my fuel injection system. Tire pressure is good. And, finally, I have never used anything but premium octane gasoline.

So, that leaves me with sensors to investigate to hopefully find the problem and revitalize my fuel economy.

Thanks again for the response as it was very informative and valuable. Good show!

Take care!

 

make sure that youre coils are not misfiring still/again (pretty common in maximas). and if youre not use to all your cylinders firing all at once then go ride in another maxima and see how you two compare.