Hello people,

 

This is my first post here.

 

I own a 2007 Škoda Fabia Elegance, 1.4 16v, it's the BBZ engine (101 bhp). 

 

I have an expensive and annoying problem with it. It's just consuming petrol as if it were dumping it down the drain.

 

This week I topped the tank. Drove it until the reserve light came on. 10.014 gallons. And I only managed to get 140.8 kms (roughly 87.5 miles) out of it. That's about 14 km per gallon (US) or 27 l/100 km. That's absurdly high. 

 

Apart from the high fuel consumption I have no symptoms of an issue. 

 

I suspect a broken coolant temperature sensor is the culprit. Do you guys have some input on what may be wrong with my vehicle? 

 

Thanks in advance. 

The ECT sensor is absolutely the first thing to change.

42 minutes ago, sepulchrave said:

The ECT sensor is absolutely the first thing to change

 

Thank you @sepulchrave, that confirms my suspicions. I'll do change it.

Location, Columbia - so I presume that is US gallons (smaller than UK gallons)

 

However your display says l/100km 24.8 - that's about 11mpg. Yup that's a lot of petrol. My 2001 Octavia, bigger car with a similar version fo the same engine (75ps) does a bit over 40mpg

 

Probably related to temperature sensor however:-

Does it drive with reasonable power - coil packs are know to fail on these engines

Does it burn oil - oil breather issues are well known

 

Edited 8 January, 20188 yr by bigjohn

5 minutes ago, bigjohn said:

Location, Columbia - so I presume that is US gallons (smaller than UK gallons).

 

US gallons indeed, sir. Roughly 4 litres each, for a total of 40 litres for 140 km. Either US or Imperial, that's a lot of fuel for the distance. 

@juanse_2691 - I'd be surprised if this isn't the ECT sensor. One question/observation you can do without any tools: Does the exhaust smell of petrol/gasoline at trip end?

2 hours ago, KenONeill said:

@juanse_2691 - I'd be surprised if this isn't the ECT sensor. One question/observation you can do without any tools: Does the exhaust smell of petrol/gasoline at trip end?

 

Thanks @KenONeill. I'd say the smell of petrol is pretty consistent. Haven't checked at trip end, but it's there at start or while running.

14 hours ago, bigjohn said:

Probably related to temperature sensor however:-

Does it drive with reasonable power - coil packs are know to fail on these engines

Does it burn oil - oil breather issues are well known

 

@bigjohn it does drive with reasonable power, only a bit laggy at low revs but as far as I'm concerned that's pretty normal for the 1.4 16v powerplants. A spark plug change is on the way though, to see if it improves performance a bit. Oil -doesn't burn to write home about- but these engines have a reputation for using quite a bit of oil. So far I haven't seen any significant oil consumption. 

Edited 9 January, 20188 yr by juanse_2691
Clarity

Just ordered the ECT sensor. It's a two connector piece with gray top. Checked it this morning. 

 

At first I thought I could use a green top, but that's a 4-pin instead of two.

4 hours ago, juanse_2691 said:

but these engines have a reputation for using quite a bit of oil. So far I haven't seen any significant oil consumption. 

 

My 1.416v is burning very little oil at 125k miles. Had a period of burning a lot of oil but that was a blocked oil breather pipe within the air filter - this pressurises the crankcase and blows oil past the valve stem seals

I think all Mk1 Fabias use the same coolant temperature sensor.

Please let us know if the new one fixes your problem.

Thanks @Wino. I'll do. Just learned that this morning when ordering the replacement part. 

 

@bigjohn that's good to know. Have new bulbs coming (Osram Nightbreaker Laser) as well as the replacement ECT sensor, so I'll be sure to clean the breather pipe just in case when I put the new parts.

@juanse_2691 Well, the smell of petrol positively confirms that it's running very rich, and the most likely cause of that is a dud EMS channel on the ECT sensor. Don't bother with the spark plugs until after changing the sensor, so as to not wet foul new plugs.

@KenONeill Absolutely! The new sensor should be arriving in the mail today so I'll change it and see how things go from there. 

Well... I don't even know what to expect after changing the engine coolant temperature sensor but so far I haven't noticed any difference. Let's see how much this week's refueling lasts. Perhaps I was expecting too much of a change OR any other component (EGR? O2 sensors? Sticky injector) is the culprit. According to VCDS nothing is wrong with my car, there are no fault codes or CELs.

 

I'll keep you posted on my "new" MPGs.

You must reset the ECU by disconnecting the battery for a while, next thing to change is the pre-cat lambda sensor if it doesn't improve.

Thanks @sepulchrave! Damn, I should've known better. Will do the resetting tonight!

Have you checked for fuel leaks? With consumption that poor, I’d be looking for a split pipe or filter. 

 

Try parking the car over some clean and dry paper (the back of a roll of wallpaper is ideal), run the car and look for signs of dampness on the paper.

1 hour ago, arry_b said:

Have you checked for fuel leaks? With consumption that poor, I’d be looking for a split pipe or filter. 

Interesting. But would the trip computer account for the leakage? I think the MFA would show normal values then. 

@juanse_2691 - I'd agree that the trip computer wouldn't detect a split pipe, because it works off distance traveled and fuel flow and return at the metering system, not tank level.

You’re right chaps, I’m not used to such modern farcles!

 

That makes the fuel consumption look very bad indeed. Good luck finding the cause.

I hope it's not expensive. The ECT sensor didn't solve the problem, judging by the numbers on the trip computer. Consumption hasn't changed a bit, though I feel the car is a little bit more responsive now -but that could be a placebo effect, anyways-. Let's see if a good injector testing and cleaning does something, and let's hope that it isn't a bad (stuck open) EGR or O2 sensor.

Quick update: I went to change my spark plugs (Putting new NGK BKR6EIX-11 iridium spark plugs) and spark plug from cylinder number 1 was caked in oil. The valve cover is out for a reseal and I'm cleaning the injection nozzles as well. Tomorrow we'll see. 

@juanse_2691 - An oil-fouled plug could also cause rich running.

 

Likely causes of oil fouling are a worn valve stem oil seal (in this case on #1) or a seized oil control ring (again on #1). Is there any indication of the car producing blue smoke, particularly when cold and/or when you pick up the throttle after a period on overrun?

@KenONeill the cause of the oil build up has likely been addressed, but no, there weren't any signs of smoke at all.