Bad fuel economy in 20v

[Bling]

i'd be in heaven if i got 500 km i think

likewise around town...

I managed over 500km on a tank driving from Christchurch to Motueka (plus other driving) with a boot / back seat full of piss, food and camping gear with a mate. So it is possible

[sergei]

In my AE101 I managed 700+ out of tank that is on 1 full tank to get to Wellington - when I was poor student.

[Punter]

I've got a really heavy foot and I get 500 ~ 550km a tank in my ae101, can manage 600 on a long trip.

Some of you guys are getting shite fuel economy.

Blacktops should be cheaper to run shouldn't they?

[Matty104]

how do i go about resetting the ecu? then ill try checking codes again

[sergei]

pull the EFI fuse out for ~15sec, from fuse box under the bonnet.
But before that, did you have any codes?

[Matty104]

filld up last nite, and had checked the codes the previous time i filld up, and had no error codes then

[gasman]

i only got about 400kms city driving in my blacktop with it running perfect with no errors or anything. driving like a nana as well

[sergei]

if you have free time 12mm spanner/socket with ratchet, jack, some safety equipment (jack stands, stumps bricks, concrete blocks), and butane torch, you can try and clean your oxygen sensor.

Remove sensor (pretty straight forward). But it in some kind of vice (vice the flange of the sensor not the body of it). Heat the sensing area with the butane torch until it is bright red hot and keep it like that for 2-5min. let it cool down, all the crap on it should flake off by that time.

Put it back in, reset ECU and measure OX1 voltage. Should fluctuate between ~1V (+/- 200mV) and 0V about 8 times in 10 seconds or more. Fluctuations are the result of the ECU constantly adjusting mixture. It does in error and trial way as these sensor have quiet steep hysteresis.

If the voltage is not fluctuating and is stuck at 1V it means that something causing ECU into overfueling. ECU can only compensate maximum 20% of the fuel correction from factory map. If it is stuck at 1V it will clog again after a while. If ECU is out of that 20% range it will run in open loop (like it does under full throttle, or low coolant temp).

The cause of that could be something simple like stuck thermostat, or faulty water temp sensor (unlikely, but possible), or wrong timing (too much advance - causing detonation - which causes ECU to overfuel and retard ignition), cam timing - either cam/crank shaft jumped a tooth or somebody did not install it right in first place (with one tooth out on exhaust cam, it will still run fine, but will be slightly under powered and cause all sorts of issues, because the camshaft and ignition timing runs off that shaft). Even wrongly set Throttle sensor can cause ECU going into open loop.

[Matty104]

wow thats alot of info to take in , kind of understand, i will have a go at resetting the codes at some stage and try elominate that and get back to you , and then get on to cleaning the oxy sensor

Matt

[Matty104]

just reset the error codes and went for a drive around the block then tested again and had no error codes, so will get round to cleaning that oxy sensor early next week, and add injector cleaner at the same time

[sergei]

Another question: how long does it take for your car to fully warm up (slightly lower than middle of the temp gauge)?

[Matty104]

about 2.5 to 3 kms in the morning before its at that level, just had a quik look under the car and from what i could reach the wires that go to the oxy sensor seemd to b just hanging and the grommets that connect it to the body (or what ever they secure to) wernt connected to anything,planning on doing the sensor tomorow morning,

just while im here , im lowering my car with adjustables, where would the lowest part of the body be that they measure from? the rails that run down kindof under the seats, or the rails that you lift up with the jack?

[Boosted_162]

Lowest structural bit, so not bumpers or exhaust, but includes chassis rails and sills.

[Matty104]

hey guys, just cleand the oxy sensor , reset everything , drove round and did the voltage and codes again and its still all exactly the same,, no codes , 2v accross vf1 and 0 accross ox1

[deaf_rattle]

i just did 495km off 35l in my ae92, mostly town driving.


but ive seen as little as 230kms off closer to 40l was fun though.

on the open road ive done about 700 off 40l

[Boosted_162]

i just did 495km off 35l in my ae92, mostly town driving.


but ive seen as little as 230kms off closer to 40l was fun though.

on the open road ive done about 700 off 40l

Damn thats good! I couldnt even manage 700km in my GT4 from its 68L tank!!

[Matty104]

so wot the hells goin on with mine then haha. hopefully its cheap tho, got to gt a cert in the nxt few weeks , what a waste of money, owell

[spark_38]

i just did 495km off 35l in my ae92, mostly town driving.


but ive seen as little as 230kms off closer to 40l was fun though.

on the open road ive done about 700 off 40l

Damn thats good! I couldnt even manage 700km in my GT4 from its 68L tank!!

the GT-4 are thirsty. I got 400km out of 68L, and that wasn't driving it hard either. when I was boosting it, was more like 350km/tank

[sergei]

from completely empty to completely full is about 70.5L on a ST205.
My first fill up was 69.8L, I barely made it to gas station. My ST205 consumes about 12L/100Km btw. My AE101 does about 8-9L/100Km with similar driving.
My ST165 does 15-25L/100Kms (err did, now it is in the garage with wiring sticking out like guts from samurai who just committed sepuku), but it has (had) got a bit more power.
Back on the topic. If you are measuring right, (Voltmeter set to right voltage range ie 2.0V max) if the OX1 voltage is 0 all the time it means your oxygen sensor is dead. Before dishing out $340 for a new one just make sure you are measuring right and there is no fault in your wiring. Remember how you cleaned it? You can test it at same time, while heating up measure the voltage across white and blue wires on the oxygen sensor it should read approx 1V constantly (or -1V depending on polarity).

[Matty104]

the volt meter was a automatic one so it should adjust to whatever i connect it to shouldn't it? is a pretty expensive one.

i will have a go cleaning and testing it again when i have some spare time,
i assume when you say test it while heating it, it (the wires) doesn't need to be connected to the car?

is that how much a new one costs?