High fuel consumption | 3SGE

[GreddyMR2]

Hi,

I hope someone could help me...
Recently started to drive N/A MR2 and it consumes really lot of fuel. It's very similar to my track mr2 which has around 300hp.

Maybe these point would shorten the list of causes:
1. Lambda was changed to Denso not so long ago
2. There is "sport" air filter and free flowing exhaust fitted
3. Brake calipers are not seized
4. Water temp gauge acts very strange. Firstly, it goes to operating temp (just a little less than half), then it sometimes goes all the way down and then goes back to regular point. I don't feel anything to engine's work when gauge is fluctuating, so I guess it's only gauge itself or sensor.
5. There are some problems with idling speed. When the car is started from cold, idle speed is around 1k rpm (at this point I think it's running very rich) and then slowly after a minute or so it goes up to normal ±1.5k rpm point. Then it slowly decreases when engine is warming, but when it's fully warm, rpm stays at around 1k. So it's a bit high.

Today morning I started a car with a fuel gauge showing half of tank and drove to work about 6km. After this "trip" fuel gauge dropped by 2 points. When I parked the car I even checked for fuel leaks as this drop really shocked me...

Any help would be really appreciated.

[Mullen]

4. Water temp gauge acts very strange. Firstly, it goes to operating temp (just a little less than half), then it sometimes goes all the way down and then goes back to regular point. I don't feel anything to engine's work when gauge is fluctuating, so I guess it's only gauge itself or sensor.

That sounds like an air pocket in the system, or at least other people whose gauges were doing that found it was an air pocket - when the air hits the sensor it doesn't read it and the needle drops.

Re: Fuel consumption, what are you actually getting out of a tank?
Have you been using the trip and noting the mileage before refilling?

[GreddyMR2]

4. Water temp gauge acts very strange. Firstly, it goes to operating temp (just a little less than half), then it sometimes goes all the way down and then goes back to regular point. I don't feel anything to engine's work when gauge is fluctuating, so I guess it's only gauge itself or sensor.

That sounds like an air pocket in the system, or at least other people whose gauges were doing that found it was an air pocket - when the air hits the sensor it doesn't read it and the needle drops.

Re: Fuel consumption, what are you actually getting out of a tank?
Have you been using the trip and noting the mileage before refilling?

I agree that there might be some air in the system, will need to do a good bleed.

Not really sure yet how much I get from a full tank, but last time I filled 18 liters and done only about 140km when I needed to refill again. And that was half city and half highway driving. And I really wasn't agressive with a throttle.

With a full tank I should drive around 300km at the moment.

[SonicSW20]

4 and 5 could be related - if there is air in the system, then your ECU temp sensor will be getting erratic readings as well. This affects idle speed and fuelling.

If 4 and 5 are unrelated, then you could have air or vacuum leaks. That will give you poor fuel economy.

[2barGee]

I found that my tubby was actually better than my old NA on fuel.

With the NA you have to work them hard to really get moving, with the tubby you can be lazy and use the torque under general driving conditons.

On track it was a different story though......70 miles to a tank on the tubby.

[GreddyMR2]

Tried to rebleed coolant yesterday (just by unscrewing radiator and heater bleeding points and filling coolant).
Still the same. Water temp gauge didn't even started to raise and stayed down all the time when I was driving to work.

Maybe it's worth mentioning that this car was standing for about 2 years unused. Maybe something is stuck...

[2barGee]

I'd be changing the thermostat mate. Only get a genuine Toyota one.

[mr2garageswindon]

Do the coolant pipes in the engine bay feel hot after driving the car? Maybe worth undoing the coolant temp sensor a little till coolant flows out to eliminate any air locks near the sensor. Be careful not to burn yourself though. Does the heater blow out hot air? Could just be a duff coolant temp sensor or gauge or stuck or missing thermostat.

[Draven]

I'd be changing the thermostat mate. Only get a genuine Toyota one.

^^ This

[GreddyMR2]

Do the coolant pipes in the engine bay feel hot after driving the car? Maybe worth undoing the coolant temp sensor a little till coolant flows out to eliminate any air locks near the sensor. Be careful not to burn yourself though. Does the heater blow out hot air? Could just be a duff coolant temp sensor or gauge or stuck or missing thermostat.

Haven't checked the hoses yet, but heater blows hot air normally. I'll be changing coolant anyways, because now I am running with water just to clean the system after long time standing.

I think I will have to check thermostat at the same time.

[GreddyMR2]

I've just remembered one thing that I didn't mention and now I think it can cause high idle and fuel consumption.
I've fitted Walbro fuel pump in advance in case I will swap engine to some kind of V6 and maybe it's overfueling a bit? Could this be the reason?

[Al-sw20]

Overfuelling the stock regulator?

Possible. It happens on the 4AGE when people fit a big Walbro because they are cheap to buy.

[GreddyMR2]

I can't think of anything else, so probably this will be the problem.
Wondering what's my best option now. I don't even want to think about taking fuel tank off again, it's terrible.
Is the only option to fit aftermarket fpr then? How about fitting 3sgte fpr?