AUIII I6: fuel consumption up by 10-20%

rowan194 · 28-08-2011, 08:45 PM

I have an AUIII Fairmont I6. My fuel consumption has gone up from the mid-high 13's, to 15's (sometimes 16's) in the past couple of months. At first I thought it was a bad batch of petrol, because it happened suddenly, but I've mixed up the outlets since and there's no real change.

No unusual friction or rubbing noises. No change in engine note. No pulling to one side. No hard auto changes. Oil is clean (has been changed routinely once since). Basically nothing is jumping out apart from the trip computer showing higher consumption.

I did have a minor misfire due to deteriorated leads, I replaced them and also the coil pack, but no change.

There is one possible thing, I replaced the sparks a little before this started happening (maybe a month?). I checked them a few days ago and they look good... not like the "bad" examples in the gregory's manual.

The engine is stock, apart from a tickford snorkel. What else might be causing the high consumption? I've read that resetting your ECU can be a bit hit and miss - mine has been reset twice since, no diff.

Time for a compression test? Thanks for any help.

edit: will first hook up an LED to the diag connector to see if it's flagging any faults, that would probably be a good place to start...

dieseltrain79 · 28-08-2011, 10:45 PM

02 Sensor ?

mongrelEF · 29-08-2011, 12:29 AM

Also:
Check the old school way too - how many km do you get out of a tank?
Vacuum leaks?
Throttle position sensor may need adjusting
Plugs won't really affect the fuel efficiency readout except through o2 sensors
Thermostat not opening? How's your temp?

blueoval · 29-08-2011, 11:12 AM

Is your car dual fuel?
Did you pregap your plugs before fitting?
As already said, could be 02 sensor.
Fuel filter on petrol may need replacing if havent been done in part 70,000km.
What oil viscosity do you use? Too thick oil can be an issue with fuel economy.
It could be a number of things....

I would do all the cheap fixes first, and do it as a process of elimination.

rowan194 · 29-08-2011, 04:13 PM

Fuel is straight petrol.

I installed the plugs as-is -- I couldn't find any info on what the gap was supposed to be, I assumed they were set up properly. I have gauges to measure the gap but I'm not sure what I'm supposed be setting them to! Where can I find this info?

(edit: I just looked in my Gregory's manual and managed to find it... 1.0-1.1mm, but that's for an EL. Is the AU the same?)

Using Castrol Magnatec 10W-40 and have been using that for years.

Fuel filter hasn't been replaced for some time (I don't think since I've had the car, about 110,000km)

Thermostat+gasket was replaced as part of my cooling system overhaul the past couple of weeks, noticed the temp is more consistent now, but no change to fuel consumption.

Transmission does have a minor leak from the rear servo gasket and also rear housing seal. Don't see any spots on the driveway but it's possible the oil is being flung onto the exhaust and burned off. Will be getting that repaired soon.

I notice the list of possible error codes includes a couple for the O2 sensor so hopefully once I rig up the LED there will be a smoking gun!

blueoval · 29-08-2011, 04:37 PM

02 sensors would be my first port of call. If you need to replace them, you can get them off ebay quite cheaply.

http://www.ebay.com.au/itm/FORD-FALC...item2eb6c5cc16

midgetyone · 29-08-2011, 05:19 PM

AU III plug gap is 1.3mm. Only the AUI was 1.1mm

rowan194 · 29-08-2011, 05:37 PM

Ok, looks like the diagnostic connector changed between the EL and AU, so the instructions in my manual are useless...

Is there a way to hook up an LED to flash codes like with an EL, or do you need specific diagnostic equipment?

rowan194 · 30-08-2011, 05:09 PM

Quote:

Originally Posted by blueoval

02 sensors would be my first port of call. If you need to replace them, you can get them off ebay quite cheaply.

http://www.ebay.com.au/itm/FORD-FALC...item2eb6c5cc16

I called Bayford spares today for a laugh... they quoted me $185. Assuming the ebay part is genuine (or even from the same manufacturer that Ford uses), how can Bayford justify a 400%+ markup?

Also found lots of people confused about why their OBD2 equipment doesn't work with the AU, seems it wasn't fully compliant with the spec until the BA. Looks like I might be out of luck there. On the EL (OBD1?) you could attach an LED and get it to blink codes at you. I may have to take it to a dealer.

blumx · 31-08-2011, 02:58 AM

The first thing I check when I get bad fuel consumption is the air filter

cheers
Keith

**Mechan1k** · 31-08-2011, 03:19 AM

Replacing the O2 sensor is not a bad idea to start with.

I'd check the air filter as well as the fuel filter too.

Checking for codes needs the use of an OBDII scanner and relevant software.

O2 sensors can start reading out of whack ... but not report a failure ... hence economy changing over time. And no fault code is reported for it.

sneaky · 31-08-2011, 05:19 AM

+1 for the air filter.
i did a trip to coffs harbour and back a few years ago and the consumption on the highway was terrible. got home and the air filter was dirty as - i should have bought one up there and changed it for the trip home..

rowan194 · 31-08-2011, 05:33 PM

Quote:

Originally Posted by Mechan1k

Checking for codes needs the use of an OBDII scanner and relevant software.

Have you actually done this? Every thread I've found so far contains people who are complaining that their OBDII scanner doesn't work on an AU, because it uses a non conformant protocol.

Have ordered an O2 sensor from ebay, and the air filter is new (4-6 weeks). Will look into the fuel filter.

rowan194 · 09-09-2011, 08:50 AM

I'm having trouble getting my exhaust manifold off (see the other thread) and was going to replace the O2 sensor while I did that...

I already tried to get out the O2 sensor with an adjustable wrench but it doesn't want to go... just slips. Not really much room for leverage either. That's why I was going to try again with the manifold off.

How do you remove the sensor? 22mm ring spanner? (if such a thing exists)

**Mechan1k** · 09-09-2011, 08:52 AM

22mm spanner from memory is what I used. It came off fairly easily ... was a bit firm at first though.

rowan194 · 09-09-2011, 08:54 AM

Quote:

Originally Posted by Mechan1k

22mm spanner from memory is what I used. It came off fairly easily ... was a bit firm at first though.

Yeah, just edited my post as you did yours... I measured the wrench gap... where do you find a 22mm ring spanner?

**Mechan1k** · 09-09-2011, 08:55 AM

I had one in a kit ages ago ... that got borrowed ... and I haven't seen since :(

**Mechan1k** · 09-09-2011, 08:59 AM

Actually ... it may have been 24mm.
It was ages ago ... I can't remember ... maybe the B-series is 24mm.
It's a Friday .... my brain is not here at the moment ... LOL

rowan194 · 09-09-2011, 09:13 AM

Quote:

Originally Posted by Mechan1k

Actually ... it may have been 24mm.
It was ages ago ... I can't remember ... maybe the B-series is 24mm.
It's a Friday .... my brain is not here at the moment ... LOL

From my measurements (wrench clamped onto the new one) it's closer to 22 than 24.

I should be able to find one but probably not from the usual suspects... all those seem to stop at 19mm.

**Mechan1k** · 09-09-2011, 09:15 AM

Maybe one of the cheaper sets in the roll-up plastic sleeves ma have a 22 in it.

rowan194 · 09-09-2011, 11:21 AM

Managed to get the exhaust manifold off, once I had it out the O2 sensor was easy to get off, like about 1/4 turn with the wrench and then I could rotate it by hand. Not sure if it was already that loose and I just couldn't get the right leverage, or my attempts at removing it previously had loosened it up a bit. Didn't do it up too tight, never know when I might have to replace it again, and I don't plan on removing the exhaust manifold just to change the O2 sensor!

**Polyal** · 09-09-2011, 11:25 AM

Yeap as the others said, FE can be improved by the O2 sensor, Filter, Ignition but also remember an engine is just a pump, look at maybe CAI and Exhaust if your keeping the car for a while.

Otherwise I find the best way to get better consumption is to not boot it off lights etc, I always drive 1/4 throttle and let the torque do the work. Around town you will just hit another red light anyway so getting there quicker serves no purpose.

Day-mow · 09-09-2011, 11:53 AM

here's a good simple CAI. will improve fuel economy and power.

after changing o2 sensor i think your we'll on your way though

Beer Baron · 09-09-2011, 03:26 PM

A stuck open thermostat will change fuel economy too, Or one that doesn't close properly. The car uses more fuel when cold starting/running.

Mine was stuck open for a while and it cost me close to 120km's a tank.

rowan194 · 09-09-2011, 03:57 PM

Quote:

Originally Posted by Beer Baron

A stuck open thermostat will change fuel economy too, Or one that doesn't close properly. The car uses more fuel when cold starting/running.

Wouldn't a stuck open thermo make the coolant temp vary since it's unable to regulate it? I replaced the thermostat about a month ago as part of some TLC for my cooling system, and once it gets to temp (on the "O" in NORMAL) it stays in that position.

I've replaced the O2 sensor now so I'm keen to see if that fixes the prob.

rowan194 · 09-09-2011, 04:01 PM

BTW... did you guys reset & retrain your ECU after replacing the O2 sensor?

**Mechan1k** · 09-09-2011, 04:03 PM

Did you disconnect the battery for a bit and reset the ECU as well????
This can help a bit as well after an O2 sensor replacement.

I just realised your extra post afterwards.
An ECU reset is a good idea ... first bit of driving will need to do some relearning.
Your 2nd tank of fuel will be a better guage if it has worked or not.

**redxm** · 09-09-2011, 04:10 PM

Quote:

Originally Posted by rowan194

Using Castrol Magnatec 10W-40 and have been using that for years.

I used to use that as well. I changed to Shell Helix 10w-30 & went from 9L/100 to a tad over 8L/100 on a trip

rowan194 · 09-09-2011, 04:28 PM

Quote:

Originally Posted by redxm

I used to use that as well. I changed to Shell Helix 10w-30 & went from 9L/100 to a tad over 8L/100 on a trip

Is that HX7 AJ 10W-30?

http://www.shell.com.au/home/content...uct_range/hx7/ (click on 10W-30 tab)

I know moving from semi to fully synthetic is going to improve economy, but I've read fully synth oils are good at dislodging gunk, and may cause leaks in older engines if it's "used to" mineral or semi synthetic? It's done just over 190,000km.

Quote:

Originally Posted by Mechan1k

Did you disconnect the battery for a bit and reset the ECU as well????
This can help a bit as well after an O2 sensor replacement.

Ah shoot, I should have asked earlier, could have d/c the battery while I was fiddling with my exhaust manifold. I'll reset it later.

Quote:

Originally Posted by Day-mow

here's a good simple CAI. will improve fuel economy and power.

Was this meant to be a link?