Crappy Fuel Economy

BADan · 04-06-2006, 10:24 PM

Hey guys,

As you can guess by the title, my car (EFII 4.0l) is, and has been getting crappy fuel efficiency for a while. City driving, at the most I will get 350k's out of the tank. I see many others on here easily getting 450k's +. Also, I am not a leadfoot at all.

I have a new fuel filter, fuel pump and it has been recently serviced (new plugs, air filter, oil).

I don't know how accurate the fuel information displayed in the car is, but on acceleration, the numbers (instantaneous) jump to very high numbers: 60,70 sometimes. When cruising, it seems to be ok, judging by the dash estimations (7-8 on the freeway). It says that the average is around 15.1L/100k, this is well below what the actual usage is IMO. Other things to note is that is does not idle very smoothly, and jumps up a bit when sitting. On a cold day last week, I noticed that the amount of air the excaust was spitting out looked fairly excessive.

What reasons could be causing this? I read a few posts on dodgey o2 sensors that can be a problem. Is taking it out, and seeing if the car runs the same the best way to test, or a multimeter like I read? Could blocked injectors cause this, or other reasons?

Sorry about the long post, but with petrol prices continuing to rise, I want to try and get rid of this problem.

Cheers.

Jet-Star · 04-06-2006, 10:55 PM

EDIT: Im a nong. Please delete.

Aaron_EF8 · 05-06-2006, 09:31 AM

The trip computer reading high figures under acceleration is normal.

Have you reset the avg L/100km counter on the trip computer? It stores the average economy since the last reset, which could be 50,000km ago. Have you done an ECU self-test to see if it has any problems? Have you checked all the vacuum hoses to see if one's split?

Info on ECU self-testing - http://www.fordmods.com/forums/documents.php?doc=52

crannersEL · 05-06-2006, 09:40 AM

Quote:

Originally Posted by dbarkho

Hey guys,

As you can guess by the title, my car (EFII 4.0l) is, and has been getting crappy fuel efficiency for a while. City driving, at the most I will get 350k's out of the tank. I see many others on here easily getting 450k's +. Also, I am not a leadfoot at all.

I have a new fuel filter, fuel pump and it has been recently serviced (new plugs, air filter, oil).

I don't know how accurate the fuel information displayed in the car is, but on acceleration, the numbers (instantaneous) jump to very high numbers: 60,70 sometimes. When cruising, it seems to be ok, judging by the dash estimations (7-8 on the freeway). It says that the average is around 15.1L/100k, this is well below what the actual usage is IMO. Other things to note is that is does not idle very smoothly, and jumps up a bit when sitting. On a cold day last week, I noticed that the amount of air the excaust was spitting out looked fairly excessive.

What reasons could be causing this? I read a few posts on dodgey o2 sensors that can be a problem. Is taking it out, and seeing if the car runs the same the best way to test, or a multimeter like I read? Could blocked injectors cause this, or other reasons?

Sorry about the long post, but with petrol prices continuing to rise, I want to try and get rid of this problem.

Cheers.

We are all in the same boat as you mate, ive had to settle to the fact that my EL is fuel hungry and the fuel eco will always hover around the 15-17L/100km. My cars had regular maintainance and $1200 worth of repairs in the last 4 months and nothings changed with fuel eco, even after extractors there was no change.

The answer is skip the 4.0L and get a small zippy 2.0L

ilsautomotive · 05-06-2006, 09:37 PM

For the low cost and ease of installation, a new/genuine Ford thermostat would be well worthwhile. My EA was getting terrible economy and that was the reason; the car was in 'closed loop' mode and running rich/cold all day long.

Hotwire · 06-06-2006, 09:42 AM

^ Agreed with trouty. My EF at the moment is getting rather average economy, and the temp is not getting over 80*C in this cooler weather. Have noticed fuel consumption going up, and as such am fitting new t/stat on Friday. Will let you know if changes at all ;)

falcon91 · 06-06-2006, 10:06 AM

Check your catalytic converter and O2 sensor! My EA was shocking on fuel. I put on extractors (and the cat was blocked) put in a new cat and o2 sensor. Heaps better fuel economy. Can't be just the extractors!

RG · 06-06-2006, 11:06 AM

Something is definately not right with those consuption figures. Definately check the O2 sensor and the cat converter. I was getting about the same consumption as you are before I replaced mine. I'm now down to 11.6 l/100k and get around the 550-600k mark per tank on the highway.

MacGyver · 06-06-2006, 06:29 PM

Same here. I'm down to 10.5l/100km combined cycle. Easy to get 500+ km out of her. All I did was install new O2 sensor and reset the ECU.

cheers
Scott

Me_3 · 06-06-2006, 07:08 PM

urk... thats worse than my v8.. (lexus 4L v8 in EB wagon, 11.5L/100k)

O2 sensors, and a few meters of vacume hoses... makes a world of difference...

Hotwire · 08-06-2006, 02:15 PM

MAP sensor is a black box on the firewall with a number of vacuum hoses running to it. Dont have a photo, but I know its not cheap to replace ($200+)

djmaker · 08-06-2006, 02:41 PM

i get about 400km out of 74ltrs of gas :S... in my eb xr8 :S....

AshMan · 08-06-2006, 05:47 PM

I'm another 300km - tank guy...

Temp never gets off cold...

MightyXR6Turbo · 08-06-2006, 09:28 PM

Yeah thats the same with my ED wagon, but thats because I have to wire the thermofans up properly, one going all the time - ED very cold.. and the MAF was rooted lol.

Well don't dispare, I was only getting 18.2L/100kms out of my XR6T last tank (I thrashed it a bit ;) lol)

coolcanberra · 10-06-2006, 08:11 PM

Check your exhaust system for leaks.

I had crappy fuel economy, then discovered my rear 2 mufflers were rotten, with holes. When I had (used) ones put in, the professional man at Roadways (highly recommended), waved a CO wand over things and used a rattle gun to eliminate the not obvious leak around the headers, and up where the cat joins the header.

Thinking back, I replaced my head gasket, by pushing the header aside, but did not bother to split the manifold and install new joiner bits, and bolted it all up again. I was leaking gasses at both ends.

Fuel economy improved.

The MAF Mass Airflow Sensor and puts out a voltage reading. My manual on p 10-1-11 fig 15 shows 0.8 volt on idle, and 2 volts at 60MPH, 1.2 volts odd at 20MPH.
MAP is for Manifold Absolute Pressure and it the box on the firewall.

BADan · 10-06-2006, 09:07 PM

I've put in a new oxy sensor. Will see how it goes. I think I have noticed a lag on acceleration that was there with the old one is gone. Does the ECU need to learn new settings with the new sensor?

Because of the cold weather, I have noticed excess exhaust fumes, possibly related?