[Ray Bell]

Normal fuel consumption in my silver Forester has been a little better than the green one. Around 620kms on a tankful (dead full to bone dry).

Two weeks ago I had to go down a road which was very twisty and climbed over lots of big hills. Naturally this inspired some spirited driving, but I was pretty mortified when I ran the tank dry at only 438kms.

Three drums of fuel later (one @20 litres, one @ 21 litres and one unknown, but estimated @ 14 litres) I was dry at 465kms - without the twisty road and hills.

So I know I have a problem. I am thinking it might be an Oxygen sensor, the airflow meter or something else which has input into the computer to change settings. If the second figure, 465kms, on regular running with approximately totalling the regular tankful - maybe less a litre or at most two - is my new 'norm', then I have a jump in fuel consumption of approximately 30%, though there seems to be no change in anything else.

Except that the exhaust smells pretty rich...

Any advice is very welcome.

 

[Ray Bell]

I managed to get a code on this, the numbers were 0031, clicked on that and got told the 'heater sensor No 1 bank' or similar, I'm told this refers to the O2 sensor of the RH bank?

I have been through several old threads and this seems to have come up before, but nobody ever actually answers the question. Any chance of some further information here, please?

 

[Kevin]

Yep, front O2 sensor. Explains the increased fuel consumption as it will run rich once the O2 sensor plays up.

 

[Ray Bell]

Found another one and installed it...

In fact, because I wasn't sure which bank went to which sensor I changed them both. Codes are clear now, I just have to check the actual consumption over the next day or two.

 

[Kevin]

Great! Let us know how it goes.

 

[Ray Bell]

Not all that well...

I have a kind of fluctuating power interruption at speed. One suggestion has been that the catalytic converter might have cried "Enough!" at the overdose of extra fuel and had a meltdown. If it's like the Nissan cat converters I've looked into before, the bits inside break up and float around and block the exhaust and that just might be consistent with the power fluctuations I'm now getting.

I did take the whole front half of the exhaust system with me when I left home the other night, so I can change this while I'm on the road during this trip and see how it goes. It really is helpful to have all this stuff lying around!

I would expect it will take me about 45 minutes to change it, I just need ramps or somewhere I can straddle a low bit of ground to give me clearance.

 

[Ray Bell]

Yes, I found the catalytic converter...

...bits that were floating around in the first muffler.

 

[BicycleMad]

The information in threads like these is priceless

 

[Ray Bell]

One thing I am now very sure of...

The ELM327 OBD2 bluetooth sender unit is a big help.

https://www.ebay.com/itm/OBD2-ELM32...m=401560337366&_trksid=p2045573.c100505.m3226

With the free download to your smartphone to use it, you can go to it any time and check what fault codes are registering. And you can remove them if they're fixed.

Mine told me that the O2 sensor was bung, then when I fixed that it told me the catalytic converter was not working to full efficiency (you might say that!) and when I put it all back together again I cancelled the codes. Today the check engine light came on again with the cruise control light blinking, I hooked up via bluetooth as I drove along and it said it detected an occasional miss on No 3 cylinder.

So I now know which cylinder to put my spare plug lead on until I get myself a complete set of new ones.

 

[Ray Bell]

...and it's now fixed!

The tankful of fuel I put in on Friday ran out tonight at 629kms. A lot of twisty roads and quite a bit of fairly quick running on better backroads. I'm a happy boy.

 

[Ray Bell]

Just to clarify a bit about those O2 sensors...

The 'front' one registers after the merging of the left and right banks of the manifolds/extractors join, so it's nothing to do with which bank.

The rear one is immediately after the catalytic converter.

So the front one's job is measuring the oxygen in the raw exhaust, the other measures the things the cat converter is supposed to modify or remove from the flow.

Now here are a couple of interesting You Tube clips:

And this one

Unfortunately, it seems those 'non-foulers' aren't available in Australia!

 

[Kevin]

...and it's now fixed!

Terrific! Thanks for the update.

 

[Ray Bell]

And a little more...

I've subsequently had three tankfuls deliver over 700kms each. Regular unleaded (91 octane here, which would be 87 there, I think) and regular driving, generally sitting on 100-110kmh.

Now I've changed the gearbox in the green Forester I've got it on the road, it's not so good, but what I found was that in trying to detect what I think is a misfire the ELM327 OBD2 gizmo wouldn't hook up to the ECU in this car. Nor a spare one I had, so then I tried them in the silver car and they don't work there now either!