umarcrespo333

Causes of poor mpg

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Hello gearheads,

So for the past few days the fuel consumption of my LC has gone up drastically. I am getting super poor MPG. previously the MPG was not a lot different from a toyota Prado. Well now, yesterday the fuel tank was topped up (180 dhs) and Jebal Ali to dubai to Al Ain and back again in the previous order the tank is almost empty, like on the last bar before E on the fuel gauge. The thing is I cant see any leaks of sort. 

So what info do I have:

The car smells of petrol all the time(driving or stopped).

This has been happening after the desert trip.

I also drilled in the straight pipe right before the catylic converter(if that could cause it).

Help? Thanks.

Also, the temp gauge on the tach always stays at cold maybe sometimes it would go a little high but always C. Why am I mentioning it is because I read somewhere that if the engine reads cold there will be more petrol provided to the engine to make it hot.IDK 

the reason I am posting my problems here is because it is better than taking it to mechanic and possibly getting ripped of. Also I don't know a good garage that does good work on cruisers for the price.

Thanks.

 

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Drilling a hole in the down pipe before the cat is a problem. Exhaust gas is not running through the full system. I.e. It's not reaching the lambda sensors. Lambda sensors analyze the exhaust gas and send a signal to the ECU to tell it how the engine is performing. The ECU in turn, adjusts the fueling to suit. If it's not getting proper lambda readings, the fueling won't be correct.

Temperature sensor is also important. If it's sending a signal to the ECU telling the ECU that the engine is cold, more fuel will be requested. This can cause all sorts of long term problems never mind the short term issue of fuel consumption.

These are both issues that you need to fix. Exhaust is easy, stick a dab of weld in the hole. Don't bother with exhaust putty, it will blow out again. Check operation of temperature sensor and fit a new one if required. They're not expensive and 5 minute job to fit. I assume you haven't done anything stupid like take the thermostat out?

Last thing, get under the car and visibly inspect the tank and fuel lines. Make sure you haven't hit a rock and punctured the tank or shook a fuel line loose. Check EVERYTHING front to back. You won't see a wet patch because petrol evaporates quickly but you will see staining.

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2 hours ago, Barry said:

Drilling a hole in the down pipe before the cat is a problem. Exhaust gas is not running through the full system. I.e. It's not reaching the lambda sensors. Lambda sensors analyze the exhaust gas and send a signal to the ECU to tell it how the engine is performing. The ECU in turn, adjusts the fueling to suit. If it's not getting proper lambda readings, the fueling won't be correct.

Temperature sensor is also important. If it's sending a signal to the ECU telling the ECU that the engine is cold, more fuel will be requested. This can cause all sorts of long term problems never mind the short term issue of fuel consumption.

These are both issues that you need to fix. Exhaust is easy, stick a dab of weld in the hole. Don't bother with exhaust putty, it will blow out again. Check operation of temperature sensor and fit a new one if required. They're not expensive and 5 minute job to fit. I assume you haven't done anything stupid like take the thermostat out?

Last thing, get under the car and visibly inspect the tank and fuel lines. Make sure you haven't hit a rock and punctured the tank or shook a fuel line loose. Check EVERYTHING front to back. You won't see a wet patch because petrol evaporates quickly but you will see staining.

Hmmm, welding not really at my disposal but the hole is really super small. 2 mm to be precise. Will a screw do the job? I think something has gotten loose. No the temp gauge is the same from the day the car was bought. And no I didn't take the thermostat out.

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Why did you drill a hole in the exhaust system anyway? 

Anyway, @Barry is right- if the ECU gets a signal saying the engine is cold, it will adjust the fuel trims to improve combustion- since ti thinks the engine is cold. This works much like a choke used to work on a carburetor, so getting the temp gauge issue fixed should be your first priority, immediately after plugging the hole in the exhaust. 

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2 hours ago, treks said:

Why did you drill a hole in the exhaust system anyway? 

Anyway, @Barry is right- if the ECU gets a signal saying the engine is cold, it will adjust the fuel trims to improve combustion- since ti thinks the engine is cold. This works much like a choke used to work on a carburetor, so getting the temp gauge issue fixed should be your first priority, immediately after plugging the hole in the exhaust. 

urm sounds cool.

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Sorry to sound crude but you are acting like a real doofus kid here, doing all sorts of stupid and dumb things in order to look and sound "cool" lowering your front suspension, drilling holes in your exhaust, WTF man! Get a grip dude. 

My advise : STOP IT ! 

The car smells of gas because it is running rich hence decreased MPG, because of that hole you drilled before the cats. Go to any cheap Irani shop give him a 20 dh note and to weld that hole up. 

I wouldn't suspect the temp sensor because Land Cruiser temp gauge hardly goes above C in peak summertime in the Desert maybe it will go up to less than 1/4 of the way up.  

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28 minutes ago, desertdude said:

Sorry to sound crude but you are acting like a real doofus kid here, doing all sorts of stupid and dumb things in order to look and sound "cool" lowering your front suspension, drilling holes in your exhaust, WTF man! Get a grip dude. 

My advise : STOP IT ! 

The car smells of gas because it is running rich hence decreased MPG, because of that hole you drilled before the cats. Go to any cheap Irani shop give him a 20 dh note and to weld that hole up. 

I wouldn't suspect the temp sensor because Land Cruiser temp gauge hardly goes above C in peak summertime in the Desert maybe it will go up to less than 1/4 of the way up.  

Urm thanks. Although I'm just a guy in the process of making. Unless I am doing a private chat with you in which you tell me what will happen if you do the following, I will keep doing this. So get ready to deal with the load of my horseshit cuz that is what we do here in carnity right?

 Also, a hole this small would cause the mpg to go down this much? wierd. I read that straight pipe makes MPG better. :/

Also I thought that you need a tune to make your car to run rich. Running rich cause backfire in the exhaust right?

Edited by umarcrespo333

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1 minute ago, desertdude said:

Well then keep suffering the consequences and the cost, eventually people will get tired of your shit and just stop responding.

And a hole in the exhaust, makes a straight pipe not! 

come on. really? :D

Well until you can please reply :D

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In theory, a straight pipe can help MPG but not by a noticeable amount. In practice, it noticeably brings it down because you’re always driving everywhere with your foot to the floor to hear the exhaust note. Been there, done that. 

There are many, many factors that can introduce a rich running condition, you don’t need a tune be it a remap or whatever. Running rich can cause pops and bangs in the exhaust but it’s not always a good thing. You will end up with a melted catalytic converter and spark plugs so black they won’t ignite the mix properly under normal driving conditions. 

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