FE just keeps droping no matter how much I hypermile

[txe5502]

I have a 1996 Nissan Maxima and it gets worse on gas everyday it seems. When I first got it back in 2005 as my first car, I ran it very hard of course. I got about 28 MPG running it moderately hard sometimes. Then I began learning how to hypermile, I started by just accelerating carefully and making sure I am always in the highest possible gear, and throwing it in N while coasting, keeping the RPM down. After I began doing EOC, P&G, etc, I was able to stay around about 32 MPG! But now I have a problem and I dont know whats wrong! Now no matter how much EOCing, P&Ging I do and no matter how carefully I acccel and no matter how high of a gear I am in I can only get 22 MPG at MOST!


Info about my car:

V6 3 liters DOHC

2 BRAND NEW O2 sensors, 1 on each bank

BRAND NEW EGR valve hose

Changed transmission fluid just a few months ago.

Tires at 40 PSI


So does anyone know what the problem could be?

[bowtieguy]

could be: injectors, fuel filter, cat converter, spark plugs, coil packs...to name a few.

if you can get to the fuel filter, it's a cheap fix to start with.

[theholycow]

Is all that EOC ok for your transmission? Could it be damaged? Most automatics aren't EOC-compatible.

[txe5502]

Originally Posted by bowtieguy

could be: injectors, fuel filter, cat converter, spark plugs, coil packs...to name a few.

if you can get to the fuel filter, it's a cheap fix to start with.

Fuel filter is the original that was on the car from 1996 as far as I know but wouldn't that cause a lean burn? My car has that "rotten egg" smell as if it is too rich!

Spark plugs/coilpacks
At night if I open the hood I can see some blue arcing under the intake manifold coming from somewhere so there MUST be an ignition leak somewhere, but there is no skipping, it runs fine as far as I can tell, still this may be something I should check into.

Catalytic Converter
I checked the intake manifold vacuum and it stays about 20" even when I rev the engine, wouldn't a collapsed cat cause the vacuum to go down on higher RPM and not up?


This is very strange the symptoms I have here. I am losing gas mileage AND power! I remember that when I first got this car in 2005 it would really burn rubber from a stop! But now when once in a blue moon that I decide to "vent" a little, I have noticed that the tires won't even break traction now! So I have less power AND less FE. But it runs JUST FINE! My dad has been working on cars since the 1960's and was considered the "Town Mechanic" back then, still works on his own car, but he tells me there is NOTHING wrong with my car (but ONLY because it runs smooth)

This dropping gas mileage has been going on for quite a while now, about a year and a half, but I think my injectors AND fuel filter might be clogged now because some idiot who borrowed my car decided to put diesel in the tank like a fool! My god it spark knocked like crazy I had to just let it sit and idle that out so it didnt destroy the engine, but I get the feeling that even though I have a fresh tank of gasoline now, maybe the diesel has clogged the injectors and fuel filter even worse.

As far as the poor FE goes, that was a problem EVEN BEFORE the problem with the wrong fuel. So that isnt the only problem.

Originally Posted by theholycow

Is all that EOC ok for your transmission? Could it be damaged? Most automatics aren't EOC-compatible.

Well, Nissan tells me that my car can be flat-towed without removing the drive-axles so I think its alright just to EOC for at most a mile sometimes. Nissan seems to be pretty good with this on their FWD models (luckily for me).


Any ideas based on this new info?

[txe5502]

Woops I forgot to mention one thing that may suggest maybe the ECU is bad!

About 2 years ago I had a 50 amp battery charger hooked up to my car. I had a voltage meter plugged into my cigarette lighter plug. While I was messing in my car the battery charger failed, but during failure, I noticed for about 10 to 15 seconds, the voltage meter got up to about 20 or 22 volts!!!! I quickly unplugged the charger! after that, my charger never worked again, and also, it fried my voltage meter, AND it fried my power inverter that I had. Could that have done some kind of electrical damage somewhere that would not throw any OBDII codes and would not disable the car or make it run bad, but just ruin FE?

[GasSavers_RoadWarrior]

Personally, I'd stick a bottle of isopropyl alcohol in the tank as a cleaner then take it out and beat the snot out of it, see where it went from there.

[txe5502]

And when you say beat the snot out of it I assume that you mean run it as hard as possible. Maybe thats a good Idea. Could acetone also work? What about this thing my dad found in an autoparts store from CRC called "Guaranteed to pass" that is a strong fuel system cleaner which the company guarantees that after using it you should pass inspection. Does anyone know if any of those might also do the trick for that?

[Jay2TheRescue]

Originally Posted by txe5502

And when you say beat the snot out of it I assume that you mean run it as hard as possible. Maybe thats a good Idea. Could acetone also work? What about this thing my dad found in an autoparts store from CRC called "Guaranteed to pass" that is a strong fuel system cleaner which the company guarantees that after using it you should pass inspection. Does anyone know if any of those might also do the trick for that?

I thought that was just alcohol with fuel system detergents added and some great marketing. Someone please correct me if I'm wrong.

-Jay

[txe5502]

Ok but what about acetone and what about alcohol? I have just poured some gasoline into a clear container with some of mom's nail polish remover (primarily acetone) and with some isoprophyl alcohol and it all seperated into 3 layers every time no matter how much I shook the heck out of it! This tells me neither of these will mix with the gasoline in my tank. So are you sure alcohol will work? And are the things I have heard about acetone doing the trick just rumors? It seems to me so far based on my tests that neither iso alcohol nor acetone will mix with gasoline.

[Jay2TheRescue]

Originally Posted by txe5502

Ok but what about acetone and what about alcohol? I have just poured some gasoline into a clear container with some of mom's nail polish remover (primarily acetone) and with some isoprophyl alcohol and it all seperated into 3 layers every time no matter how much I shook the heck out of it! This tells me neither of these will mix with the gasoline in my tank. So are you sure alcohol will work? And are the things I have heard about acetone doing the trick just rumors? It seems to me so far based on my tests that neither iso alcohol nor acetone will mix with gasoline.

Alcohol does mix with gasoline... In my area you can only purchase blended fuels... 90% gasoline, 10% alcohol. E85 is 85% alcohol and 15% gasoline. Fuel line antifreeze is alcohol as well. Drug store variety isoprophyl alcohol is watered down, so that may not mix with gasoline well. I'm not sure about the nail polish remover. There are other additives in it. These could be interfering with allowing it to mix with the gasoline.