Poor fuel economy - where to start?

[gmacrae]

fuel filter in my UCF20 basically required draining the tank, pain in the ass, wait till it's empty if its in the same spot and be prepared to catch it all

[solitaire]

fuel filter in my UCF20 basically required draining the tank, pain in the ass, wait till it's empty if its in the same spot and be prepared to catch it all

good point, just in front of the rear wheel?

[gmacrae]

mine is right up high under the tank, was too tricky to plug the hose as it was pissing out so just left it to drain into a clean oil pan

[solitaire]

mine is right up high under the tank, was too tricky to plug the hose as it was pissing out so just left it to drain into a clean oil pan

they dont make it easy eh? all the engine covers on mine make changing leads/plugs/dizzy a chinese puzzle... drives me mad, everything has to be put back in a particular order.

[solitaire]

Ok, drove to work today. Exactly the same conditions and driving style.

And its missing/bucking/getting generally pissed off even more than before.

So whats next? O2 sensor(s) i guess? Or should i ditch the k&n or maybe replace the ignitors?

The leads were rooted though so good to replace them.

[gmacrae]

plug it in man, see what the computer says, it'll cost you ten bucks if you find a nice mechanic with a scantool

[solitaire]

plug it in man, see what the computer says, it'll cost you ten bucks if you find a nice mechanic with a scantool

Ok, so it will show more than simply bridging the terminals and doing the dashboard disco routine?

My neighbour works at pitstop, maybe he has one.

[sergei]

Ok, drove to work today. Exactly the same conditions and driving style.

And its missing/bucking/getting generally pissed off even more than before.

So whats next? O2 sensor(s) i guess? Or should i ditch the k&n or maybe replace the ignitors?

The leads were rooted though so good to replace them.

Don't replace random bits... you can check O2 sensors if they are working properly (it is very easy for narrow band, not sure for wide band).
If it is missfiring, the coils might be suspect.

[gmacrae]

plug it in man, see what the computer says, it'll cost you ten bucks if you find a nice mechanic with a scantool

Ok, so it will show more than simply bridging the terminals and doing the dashboard disco routine?

My neighbour works at pitstop, maybe he has one.

not certain, but I think it will. Worth a look at least.

[solitaire]

Don't replace random bits... you can check O2 sensors if they are working properly (it is very easy for narrow band, not sure for wide band).
If it is missfiring, the coils might be suspect.

Oh ok... can you point me to where I would find the testing proceedure? I don't have a 1uz engine repair manual so unsure of the proceedure.

No way to test coils I am guessing?

not certain, but I think it will. Worth a look at least.

Ok will see what I can dig up.

[sergei]

Don't replace random bits... you can check O2 sensors if they are working properly (it is very easy for narrow band, not sure for wide band).
If it is missfiring, the coils might be suspect.

Oh ok... can you point me to where I would find the testing proceedure? I don't have a 1uz engine repair manual so unsure of the proceedure.

No way to test coils I am guessing?

not certain, but I think it will. Worth a look at least.

Ok will see what I can dig up.

Any common narrow band sensor can be tested with propane torch and multimeter. You should get ~1V (on sensor wires) when flame is applied the the business end of the oxygen sensor.

[solitaire]

Ok, I swapped the plugs and while the car seemed a bit "happier" (placebo effect?) it did not stop the missing at 50% throttle.

So a day or two ago I dismantled the maf and gave it a good going over with crc contact cleaner and so far it has not missed or hesitated.

I just filled up so will see what mileage i get out of it this time.

I also replaced the fuel cap gasket which i believe was not sealing, given that it takes me a good 3 weeks to go through a tank of gas i wonder if it was evaporating as well?

[sergei]

Ok, I swapped the plugs and while the car seemed a bit "happier" (placebo effect?) it did not stop the missing at 50% throttle.

So a day or two ago I dismantled the maf and gave it a good going over with crc contact cleaner and so far it has not missed or hesitated.

I just filled up so will see what mileage i get out of it this time.

I also replaced the fuel cap gasket which i believe was not sealing, given that it takes me a good 3 weeks to go through a tank of gas i wonder if it was evaporating as well?

After cleaning MAF it is good idea to reset ECU to get rid of dodgy long term fuel trim maps.

[solitaire]

Ok, I swapped the plugs and while the car seemed a bit "happier" (placebo effect?) it did not stop the missing at 50% throttle.

So a day or two ago I dismantled the maf and gave it a good going over with crc contact cleaner and so far it has not missed or hesitated.

I just filled up so will see what mileage i get out of it this time.

I also replaced the fuel cap gasket which i believe was not sealing, given that it takes me a good 3 weeks to go through a tank of gas i wonder if it was evaporating as well?

After cleaning MAF it is good idea to reset ECU to get rid of dodgy long term fuel trim maps.

Oh good suggestion, i cleared it recently but did not do it after cleaning the maf. I will do that before i drive home, 30 seconds should do it right?

[sergei]

Ok, I swapped the plugs and while the car seemed a bit "happier" (placebo effect?) it did not stop the missing at 50% throttle.

So a day or two ago I dismantled the maf and gave it a good going over with crc contact cleaner and so far it has not missed or hesitated.

I just filled up so will see what mileage i get out of it this time.

I also replaced the fuel cap gasket which i believe was not sealing, given that it takes me a good 3 weeks to go through a tank of gas i wonder if it was evaporating as well?

After cleaning MAF it is good idea to reset ECU to get rid of dodgy long term fuel trim maps.

Oh good suggestion, i cleared it recently but did not do it after cleaning the maf. I will do that before i drive home, 30 seconds should do it right?

yeah, should be fine. You will know if it was cleared, once you start it afterwards it will idle higher than normal for a short while.

[solitaire]

Ok so a bit of an update.

Fuel economy after cleaning the maf was still around 12.5L/100kms BUT the nasty hesitation more or less went, putting 95 instead of 91 in it killed off the hesitation all together.

I then went to the car the other week at about 2pm to discover petrol literally pissing out the filler flap (tank was 3/4 full at the time), spent a fair bit of time trying to figure out why so much pressure was being created only to discover some dick had made a hole in the fuel cap?

Why would someone do that? Definitely a shitload of pressure being held back now judging by the noise it made when i went to fill it from empty today.

will see how far this next tank gets me.

[allencr]

What's the compression?
Air in the tires & no extra concrete blocks in the boot/trunk?
Ethanol gasoline/petrol mix changed? Poorer kilometerage then straight petrol.

[RomanV]

Someone might have put the hole in the fuel cap if they had removed the charcoal cannister setup etc...

Is all that still there?

[XS1V]

Ditch the K&N, no good with air flow meters at all

Brad

[solitaire]

Someone might have put the hole in the fuel cap if they had removed the charcoal cannister setup etc...

Is all that still there?

Good question, i have no idea where it would be, the engine bay is full. According to the toyota book it should be where the battery is located, but then if i look at the next model up (20 series) it should be under the battery - my car seems to be a bastard hybrid of the ucf10 and 20 in a lot of ways and I know there were '94 ucf20's as they changed model at the end of '94.

I am guess my ls is the bastard child of just in time production and the charcoal canister is under the battery, i will have to have a look on the weekend.