Thomas.B Posted July 3, 2011 Share Posted July 3, 2011 (edited) Ok so I have changed the 02 sensor and the sparkplugs (also the oil, oilfilter, diff-oil and Autobox oil). Still the car seems way to thirsty, was driving very moderate with only 1-2 overtakings other then that kept to about 60 and some driving in town. Came 28.3 miles and filled up with 9,45 liters of gas. It comes to just above 2liters/10-km or 0,4liters every Mile. Is this normal? It should be a Jspec and only have 1 o2-sensor right? I was going to put the cat back on for the MOT and found another sensor looking like an 02 sensor, this was just put up out of the way with wire.... could this be the issue? Image is found here (http://www.imageupload.org/?d=1AF603E11) big picture so dont want to link it in. If this is an extra 02 sensor, can I work around this so the ECU wont get more readings from it? Edited July 3, 2011 by Thomas.B (see edit history) Quote Link to comment Share on other sites More sharing options...
JamieP Posted July 3, 2011 Share Posted July 3, 2011 Works out 13mpg? thats not normal, worse than the black beast:d Quote Link to comment Share on other sites More sharing options...
stevie_b Posted July 3, 2011 Share Posted July 3, 2011 Yes, Jspec TTs only have 1 O2 sensor. you're using about double the fuel that you should be (expect 26mpg from an economically-driven supra). Quote Link to comment Share on other sites More sharing options...
secondjump Posted July 3, 2011 Share Posted July 3, 2011 I was going to put the cat back on for the MOT and found another sensor looking like an 02 sensor, this was just put up out of the way with wire.... could this be the issue Image is found here (http://www.imageupload.org/?d=1AF603E11) big picture so dont want to link it in. If this is an extra 02 sensor, can I work around this so the ECU wont get more readings from it? Looks like the Cat sensor. I've tucked mine out of the way too Quote Link to comment Share on other sites More sharing options...
Thomas.B Posted July 3, 2011 Author Share Posted July 3, 2011 Looks like the Cat sensor. I've tucked mine out of the way too Ok so nothing that is needed for any function? I can just weld the hole in the cat for it? But still, any ideas on what is causing it to drink so f-ing much fuel? Quote Link to comment Share on other sites More sharing options...
Thomas.B Posted July 3, 2011 Author Share Posted July 3, 2011 Works out 13mpg? thats not normal, worse than the black beast:d Exacty, and for only being a full BPU Im not very impressed Could it be the whole ECU that needs changing? Before I changed the o2 sensor I only came 130miles on 65-70£ (gas is 1.40£/liter) so somewhat better now but still sucks. Was thinking of driving it to see some friends far from me when my vacation starts in 2 weeks so would be nice to fix whatever is wrong.... When resetting the ECU, should I drive away directly? Or does it need any certain way of driving to set itself? Not that I think it'll help to reset again but worth a shot maybe.... It does pull strong, maybe abit slower then what I would like until it hits boost. Quote Link to comment Share on other sites More sharing options...
wile e coyote Posted July 4, 2011 Share Posted July 4, 2011 pull the ecu fuses then drive for approx 50 miles for the ecu to relearn Quote Link to comment Share on other sites More sharing options...
Thomas.B Posted July 4, 2011 Author Share Posted July 4, 2011 pull the ecu fuses then drive for approx 50 miles for the ecu to relearn I disconnected the battery for 15-20min and then had it on idle for 5-10min and drove for a couple of miles. Would this really matter? Might it drink less petrol for every mile I drive? As it is somewhat lower now. If this is the case that would be really strange and everytime the battery gets low youll have to drive 50miles to get it to be normal...? Strange that the ecu is so ancient when everything else seems to be very "high-tech" for its age. Quote Link to comment Share on other sites More sharing options...
sdistc Posted July 4, 2011 Share Posted July 4, 2011 What about a boost leak? Quote Link to comment Share on other sites More sharing options...
Thomas.B Posted July 4, 2011 Author Share Posted July 4, 2011 What about a boost leak? The boost comes to 1.2 without any problems so dont think so, pulls fine and everything just a drag to "wait" for boost RPM. Quote Link to comment Share on other sites More sharing options...
richarde7927 Posted July 4, 2011 Share Posted July 4, 2011 Have you got any of your brakes binding on ,as i was getting low mpg and my brake were sticking on . Rich. Quote Link to comment Share on other sites More sharing options...
Thomas.B Posted July 4, 2011 Author Share Posted July 4, 2011 Have you got any of your brakes binding on ,as i was getting low mpg and my brake were sticking on . Rich. "Sadly" all weels are easy to push around by hand. I am really clueless as to what it can be and it pisses me off Could the ECU be bad? Any ideas or maybes? It does not leak any gas as the fuelpump does not load anything (after the first load) when having the key on and its clean underneath. I really need it fixed before the MOT as the values will be completely off.... Quote Link to comment Share on other sites More sharing options...
Konrad Posted July 4, 2011 Share Posted July 4, 2011 I'm not 100% sure, but i think that dodgy fuel pressure regulator might play a part in poor fuel economy. Where you got your O2 sensor from? Quote Link to comment Share on other sites More sharing options...
Durandal Posted July 4, 2011 Share Posted July 4, 2011 I had a low mpg problem that ended up being leaky banjo fitting at the fuel pump. Didn't see any leaking underneath because the gas was bleeding out slowly and evaporating. Quote Link to comment Share on other sites More sharing options...
KrisM Posted July 4, 2011 Share Posted July 4, 2011 I had the very same problem. 10-15mpg. I changed the o2 sensor, reset the ecu and drove 60 miles of varied driving in one turn. Now getting 24+. Toyota or aftermarket sensor? When the car is at idle go to the passenger side and stick your nose under the sill and see if you get a strong smell of fuel. Cars are getting on and fuel lines can and do rot and go porous. Quote Link to comment Share on other sites More sharing options...
Hellstrom Posted July 5, 2011 Share Posted July 5, 2011 well, Fuel pressure regulator or something wrong with the returnline from the FPR. esiest way is to install a fuelpressure gauge and see what readings you get. if its higher then normal its probebly a faulty FPR. Quote Link to comment Share on other sites More sharing options...
Thomas.B Posted July 5, 2011 Author Share Posted July 5, 2011 hmm will have to look into this, but how can it give to much fuel if its faulty? Wouldnt the ECU try and correct it and I would get an error code or something? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 6, 2011 Share Posted July 6, 2011 Measure the output voltage from the MAP sensor at idle and at cruise and post the results. Check the MAP sensor hose and anything that has been T'd off it have no splits or leaks. Has it got a new thermostat in it? If it runs too cool it will use a lot more fuel. You need a good garage to check all the sensor outputs. Quote Link to comment Share on other sites More sharing options...
Thomas.B Posted July 6, 2011 Author Share Posted July 6, 2011 Dont think the thermostat can make it drink double the amount it should. Also it drank more before I started the change (before 2.5liters/swedish mile, now 2). If the mapsensor is bad then it shouldnt run so good and I would have trouble getting good boost. I get 1.2bar without hesitation. I have booked a time to get a error-code search if I cant find the problem myself. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 6, 2011 Share Posted July 6, 2011 OK, I'll shut up then, you seem to have the job sussed Quote Link to comment Share on other sites More sharing options...
Thomas.B Posted July 6, 2011 Author Share Posted July 6, 2011 I did not mean to come off cocky in any way m8. Its just that what I've learnt the MAP sensor will make more then just fueling f*ed up. Please do tell if its any other way as I do want to learn. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 6, 2011 Share Posted July 6, 2011 If the MAP sensor is outputting the wrong voltage for the pressure / vac applied, or the pressure / vac signal source has a leak, it could well over fuel, yet still give pretty normal boost and good power. Also if the t/stat is opening too soon a low engine temp will have it running on a rich part of the map. Again, pretty normal boost and power, but bad economy. The only way to see is to measure resistance of the ecu water temp sensor and voltage from the MAP sensor. Quote Link to comment Share on other sites More sharing options...
Thomas.B Posted July 6, 2011 Author Share Posted July 6, 2011 Thanks I'll try to get time and do it as soon as possible. Do you know where I can find the info on where on the ECU/MAP I should measure? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 6, 2011 Share Posted July 6, 2011 Resistance of water temp sensor at varying temps below: http://www.mkivsupra.net/vbb/showthread.php?238522-2JZ-sensor-resistance Post #2 I have MAP sensor figures but not to hand. Quote Link to comment Share on other sites More sharing options...
NathWraith Posted October 3, 2012 Share Posted October 3, 2012 sorry to bump and old thread but at least I searched! Had both my O2 sensors done (Uk spec) and MPG is still poor, so I have reset my ECU tonight by removing the fuse etc. I'll update you guys to whether my economy improves! (17mpg atm stock UK spec) Quote Link to comment Share on other sites More sharing options...
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