Real bad fuel consumption, rev 3 Turbo

[Mr2Madlad]

Hi all

Got a rev 3 turbo had it for 10 years now, but over the last 3 weeks the fuel consumption is really going up.

I an now only getting around 100 miles from a full tank where as before it was 280 ish, its now around 25 miles per 1/4 of gauge.

There are no leaks in pipes or tank, no smell of petrol, I have changed dizzy, and rotor arm, plugs & leads, oil and filter change, nothing seems to of helped.

Compression test comes back ok as well.

Car seems to run and pull as normal.

Even jacked car up and seen if breaks are binding but all wheels spin freely and easy.

Thinking possibly 1 injector may be stuck slightly open / leaking or Lambda dead or possibly thermostat - cabin heat warms up quick as normal.

Car is in locked garage and no one is nicking the fuel overnight !

Any thoughts out there as to what it might be ?

[Adam86]

Wow thats track day consumption lol.

My knock sensor failed earlier this year and my fuel consumption increased but not to your level.

[Peter Gidden]

Error codes?

Has garage done CO test? If so what was result? If 02 sensor is bad fuel consumption will be bad.

[2mad]

Lambda would be my thinking .. hope you sort it

[Mullen]

Error codes?

21 is Lambda.

[Mr2Madlad]

No errors at all on dash with link in diag port.

My Lambda is heated 4 wire type.

2 black wires are open circuit think these are meant to have a low resistance not sure how much effect the missing heating will have once engine is running.

The other 2 Blue and white read naff all, not open but high value

Went to scrapyard at lunch and found a possible substitute on a W reg Avensis with same plug and colour wires in same place, its pretty new (only 8 months old as service book with receipts and one of Lambda replacement was in glove box), even had the butterfly mount like my original has so had that for a couple of quid.

Heater (black wires) read 2 Ohms on this "new" one so looks better.

White and blue high again.

Plugged it in (not fitted to exhaust just holding it) and started engine just to see what it would do and end got red hot in a matter of seconds so assume this is normal for a working heated lambda.

Its a DENSO DOX-0251 Lambda with Toyota P/N the actual sensor probe bit cover only has 8 holes in it where as my original has loads will this cause an issue does anyone know ??

Am thinking of trying it and see what will happen / if fuel consumption improves unless anyone thinks this is a bad idea ??

I try to avoid garages like the plague (as I fix things myself where possible) so its not had an emissions test yet, but will see if I can get one done with both Lambda probes 1 at a time at my work buddy's mates garage one evening this week.

Cheers for reply's thus far

[Peter Gidden]

So not tested the one in your car?

[Mr2Madlad]

Hi all

Finally sorted the tubby, it was indeed the Lambda probe, fitted a brand new one and got her all warm then disconnected battery reconnected it took her for a good long hard drive so se learns herself again and now get 300 miles a tank.

I cut the old probe open to see what's inside, there is quite a bit in one actually was surprised.

Mine had 2 wires the black pair that had come completely off the Zirconia probe tip these are the heater wires that warm the probe up when engine is first started to get it to temperature quick so it can enter its loop quicker to save fuel and keep emissions down.

The probe end has a metal cage over it's tip under that there is a pours ceramic cover that keeps the Zirconia protected but allows the oxygen though to the Zirconia tip, the tip is grounded by a fitted metal collar which is in direct contact with metal casing held in place by large spring which is then press moulded into metal case.

white wire is spot welded to metal housing so ground and blue is the signal output from the probe, see attached photos.

On oscilloscope the waveform looks great where as the old one was virtually flatlining.

So anyone ells who is getting bad MPG and a service does not cure you will want a new Lambda.

DOX-0226 is the one I now have fitted to my 1994 REV 3 Turbo (and fits all 1994 - 1999 turbo REV 3 - REV 5), heater DC residence is 12 ohms which is correct, (some are 2 - 10 ohm which will upset the ECU), its a Denso part (like the original) has same butterfly flange with holes, same plug on the end and same colour wires, was £44 off the electronic bay brand new sealed in packing a bargain.

Hope this helps.

[2mad]

Glad its sorted buddy