[Mk2] [Turbo] MPG issues, is there something wrong?

[Apocalypse]

hi guys, just trying to gain some opinions.

My MPG ain't been too great averaging 180 miles to a full tank. So I had a service done where I changed the Spark Plugs, Oil and Filter, HT leads, Rotor Arm, Distributor Cap and Lambda Sensor.

Filled a full tank, was hoping to get loads more miles but pretty much the same, 190 and with 100 of those miles on motorways.

I put in 20 litres last week,.. been driving steady,... not going over 3000 rpm,.. no turbo use and only got 80 miles.

Any advice?

Thanks

[nitric4k]

sounds about right, 200 miles to a full tank

[Razor04]

yeah i get about 200 miles to a tank. P**s poor really

[Slarty]

yeah i get about 200 miles to a tank. P**s poor really

I recently got 300 miles to 43L of petrol Granted, mainly motorway driving but even around town I'll get comfortably over 200

@OP, the only thing I can think of is to check the CAT and the exhaust, make sure neither has collapsed and is causing a restriction.

[ancient mariner]

i average between 250 to 300 miles on a full tank,and given the chance am quite heavy on the right foot.
imo anything less than 250 to a full tank,something isn't right.
that is of course under normal driving situations. paul.

[nitric4k]

i used half a tank the other day i only went 15 mines with my foot solid on boost

[Moo]

180 to a tank is bad. I see between 250 and 300 with varied driving.

Sounds almost like the o2 sensor is playing up. Have you checked the ECU for codes? What o2 sensor did you use, stock or after market? Aftermarket 02 sensors have been known to fail almost straight away.

http://www.imoc.co.uk/forums/viewtopic. ... highlight=

http://www.imoc.co.uk/forums/viewtopic. ... highlight=

It's a long shot but you could also check the air box sensor is connected/operational. I remember leaving mine disconnected once and it destroyed my mpg.

A blocked air filter element wouldn't help fuel economy either.

[Apocalypse]

Hi guys,

Thanks for the responses.

I bought an 02 sensor from Rogue and service and everything fitted at Pacific Works. Going to try checking for error codes. Can I cause any damage by doing this cause I usually screw things up.

Also, how do I check airbox connection? I have a Blitz SUS, would that still have a connection?

Thanks

[Razor04]

On the Blitz SUS the hole for the sensor is on the backplate of the induction cone, you have to utilize the rubber bung off the OEM airbox to seal the sensor plug into the hole.

[Apocalypse]

Awesome, gonna have a look now

[Apocalypse]

ok,.. so I've checked the sensor which was fine... and i checked for error codes too and none were detected. Does that mean that the o2 sensor is fine?

I was thinking of resetting the ECU too, would this make a difference?

[black gts]

02 sensor can be broken and with no codes showing on ecu
it happened to me

[Moo]

My mpg went through the roof in the past and it took six months for the ECU to show an o2 sensor code. An ECU reset is certainly worth a try but it still could be a dodgy o2 sensor. It's a tricky one for sure, I guess one way to find out is to swap the o2 sensor and see what happens but that will involve more cost/hassle etc and isn't guaranteed to fix the problem.

Do you know if the new o2 sensor you just had fitted was a Toyota one? How old is your air filter, what condition is it in? Also worth speaking to Luke and get his take on your fuel economy.

[Marf]

Any advice?

Is your car warming up correctly?

I just had to change my thermostat as it was sticking open, which meant the engine was spending longer running warmup fuelling, reducing MPG.

[Apocalypse]

Car is warming up fine,... a couple mins and its off the mark, about 6 or 7 and its halfway n stays there. I changed thermostat earlier this year.

02 sensor was not toyota model, a generic one that rogue supply. Is there any way to test them??

The filter looks fine, but giving at a clean out won't hurt I guess

[Razor04]

Are you running the stock cat or an aftermarket downpipe?

[Apocalypse]

Aftermarket downpipe, no idea which one, no details on it... was on the car when I bought it.... does it change anything?

[Razor04]

My rev3 runs even richer (it stinks) and my fuel economy worsened a bit after i fitted my berk tech downpipe.

This may be contributing to your problem. I take it your 4 wire lambda sensor is BOLTED into the top of your aftermarket downpipe?

Also just going on something i was told a while back, the generic or blueprint lambda sensors aint all that, i think oem is the way to go with the lambda sensor. You could try buying one of one of the people breaking mr2's on here and just try it out, see how it performs.

Rev3's have 4 wire lambda sensor i think rev 1/2 have 2 wire.

[Apocalypse]

Ok cool, thanks for the info, I may look into replacing o2 sensor again then lol,

Another year... still gonna be poor lol

[eurosmith]

Don't jump straight in and replace your o2 sensor. Get the multimeter our and test it first using the grey earth wire and the black output signal wire, you should be seeing a voltage fluctuation of around 0.6/7V at idle eg. 0.2V - 0.8V. Thats only a general rule but if you imagine it as a graph plot of voltage against time you should be seeing a peak (0.8ishV) to trough (0.2ish) time of around 0.5 secs or peak to peak of around 1 second.

Also whilst testing the o2 output get a friend to rev the car and check for the sensors reaction time, it should compensate for rich/lean fuelling almost immediately if the sensor is in good working order.

Hope this helps, if you can get hold of some data from an autodata book/disc etc and test your ECU coolant temp sender's resistance as this would surely cause poor MPG.

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