Help again! Polo 6n 1.4 Very high consumption

[Jasondj]

Hello again,

So i had this issue a while ago and went away but now its back and even worse

Current fuel consumption driving mainly 80/20 Town/Freeway driving i get 7.1km/l and mainly open road i get around 10.3km/l. I use to get around 9.5km/l and 13km/l.

I have checked the spark plugs and they almost look lean, little on the light brown side. According to a VW technician at Barons that is a sign of a healthy motor (sitting at 309000km) but he also said that type of economy is a little to high for these cars.

I have replaced the following: Coolant Temp sensor, MAP Sensor and took the car in again to a different guy for timing.

What can be the issue? Computer box giving in? I do get a strong smell of fuel on a cold start but after few second it goes away.

With my little knowledge on cars a car that's over fueling will but the spark plug black?

The guy that did the timing said that these cars really don't give out any readings or error codes. He plugged it in to bring up the revs while doing the timing and also scanned for codes and nothing came up.

Any help or advice will be appreciated

[Jetta2]

Is that according to the on board computer telling you the consumption?

Rule Number 1: never trust those consumption figures.
Easiest and most reliable way is to fill up the tank, then drive until it is empty, then work out consumption. Do that a few times to get a reliable figure.

[Jasondj]

Unfortunately these models does not have that luxury

Your suggested method is exactly how i do it.

Did some research and so far it looks like it my be the TB but very difficult to say as all the motors in the 6n and 6n2 model over the ocean was different but got a few having similar issues.

[panic-mechanic]

Impossible to comment. One needs to see what the fuelling numbers look like on a dyno under load.

[smitbrandon]

That is rather high for a 1.4? You aren't running a open cone filter right next your engine block by any chance? This also causes running rich on fuel and you run on hotter air which results to less power in essence leaving you having to press the throttle a little more resulting in more fuel usage.

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[Jasondj]

Standard filter box and GUD filter.

One thing i did notice the other day when cleaning the TB when i started the car the butterfly was vibrating like the TPS struggling to find idle speed but the motor revs did not increase or decrease at all like i've seen some say searching for revs, motor was stable at lets say 900rpm. Can see the motor shaking a little like a vibration as the butterfly was moving. I would say the butterfly movement was around a mm or 2. Does this mean my TPS is shot?

I phoned GW and they say its a sealed unit so need to buy the whole complete TB but its R2800

[panic-mechanic]

no the idle motor is not connected to TPS. If the tps side is shot it won't show the throttle position percentage in reading blocks.
So check that.

[Jasondj]

Ok, had the car at a auto service centre around the corner from me. They had the car for two days and did all kind of checks with no errors.

They recommended i book it in for a injector clean as the car is currently on 309k. The car does have a rough idle in the mornings and as the car heats up it smoothens out.

Can dirty injectors cause that?

I believe them in a way as they had the chance to milk me and say its by TB or some other electronic part and they came back to say there's no errors and recommend a injector clean of R950.

They also said i can do a small test at home. I can buy at Midas Wynn's Petrol Injector Cleaner and add that to my tank and Wynn's Fuel System Cleaner to clean my TB and intake as according to them it can/is dirty.

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[Jasondj]

Here is a video i took few days back with the issue regarding cold starts.

This only happens when the car stood over night or for 10 hours and more.

https://youtu.be/YjFxrgAQr2U

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[Jasondj]

Yesterday i took it to a guy in Grabouw who also did a test and picked up 0 errors or faults.

I brimmed the tank drove 15km and filled it again before setting off to Grabouw. Got back drove a few km here and when the clock hit 210km i filled her up again and car gave me 9.72km/L. Ill say i drove 80% highway.

I know Sir Lowrys Pass will drain a lot of fuel on a 1.4 weighing 1 ton with AC on and 3 people in the car. So if it was a flat road all the way i think the car will do 10.5km/l. Flat long open road i use to get 13km/l plus.

The video i posted clearly shows something is wrong but vagcom not picking anything up.

I did a sparkplug change before i left as they guy wanted to see the plugs but i felt i could just as well change them. According to him the plugs are perfect and there's no indication of over fueling. I will post a pic of the plugs in a min.

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[Jasondj]

They did just under 10 000km. I changed the airfilter also. Wasn't dirty at all.

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[panic-mechanic]

I have said it a million time and say it again.
Diagnosing an issue like that does not comprise of looking at faults and declaring the thing healthy.
You need to get it on a dyno and see what it does for feulling under load.
That consumtion is about normal for what you are driving and the conditions 3 people plus aircon in that car ain't never going to give you anything better than that.

[Jetta2]

Go Google on the proper way to do a plug chop.

Taking plugs out after driving, idling and what not and looking at them says nothing.

[Jasondj]

I have said it a million time and say it again.
Diagnosing an issue like that does not comprise of looking at faults and declaring the thing healthy.
You need to get it on a dyno and see what it does for feulling under load.
That consumtion is about normal for what you are driving and the conditions 3 people plus aircon in that car ain't never going to give you anything better than that.

Then the places here in Cape Town needs to get there act in order. All the "best" places I've contacted and all of them laugh when i ask them to see the fuel consumption under load on the dyno. They all say we plug it in, if there's error codes then what's giving the error is the issue. I would have accepted that mileage if i bought the car and gave me that. Low consumption. I use to get 720km on a full tank. Now i just get over 400km. Ill see who else will be able to assist me. Like i said, now one is willing to help as the majority say my foot is the heavy of the traffic in Cape Town got worse...

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[Jasondj]

Go Google on the proper way to do a plug chop.

Taking plugs out after driving, idling and what not and looking at them says nothing.

The guy i went to in Grabouw is apparently a "VW boffin". He said first thing to do is check the plugs, if they black the car over fuels in normal conditions, if they black and wet the car is using oil and if they brown to grey colouration the car is perfect and to light might mean the car is running lean.

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[Jasondj]

My main concern now is the cold start issue. No errors but clearly like in the video a person gan hear something not right

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[panic-mechanic]

The video is a missfire. That is caused by one of a few things.
Either there is a leaky injector that drips fuel in the cylinder overnight.
or the system pressure drops and the pump does not prime so it take a bit to build fuel pressure
or the temp sender is sending a false value
or you have a cylinder head gasket that is leaking water onto the piston overnight.

So do the following.
1 ) have the injectors tested
2) get a fuel pressure gauge - see what the pressure does on startup.
3) I know you changed it but get one form VW and see or borrow from a car that is OK
4) remove the sparkplugs one morning before cranking and let somebody swing it. See if water comes out of one of the cylinders.

Mechanical faults are not recorded on VCDS. One has to do some investigation instead of just plugging a computer in. That is why there are so many issues around cars being repaired these days. Nobody has a clue of how to actually diagnose stuff.

for the consumption issue - buy yourself a proper wideband air/fuel ratio meter.
Get a exhaust shop to weld a bung in. Install it and see what the fuelling looks like when you drive.
Very lean or very rich will both be heavy on fuel.

[Jasondj]

The video is a missfire. That is caused by one of a few things.
Either there is a leaky injector that drips fuel in the cylinder overnight.
or the system pressure drops and the pump does not prime so it take a bit to build fuel pressure
or the temp sender is sending a false value
or you have a cylinder head gasket that is leaking water onto the piston overnight.

So do the following.
1 ) have the injectors tested
2) get a fuel pressure gauge - see what the pressure does on startup.
3) I know you changed it but get one form VW and see or borrow from a car that is OK
4) remove the sparkplugs one morning before cranking and let somebody swing it. See if water comes out of one of the cylinders.

Mechanical faults are not recorded on VCDS. One has to do some investigation instead of just plugging a computer in. That is why there are so many issues around cars being repaired these days. Nobody has a clue of how to actually diagnose stuff.

for the consumption issue - buy yourself a proper wideband air/fuel ratio meter.
Get a exhaust shop to weld a bung in. Install it and see what the fuelling looks like when you drive.
Very lean or very rich will both be heavy on fuel.

Sound advice thanks Panic.

Yeah the mornings it does idle rough and when it idling roughly if i give petrol it misfires like that.

Car is booked at a place in Bellville for tomorrow. They will be putting it on a dyno to see.

I also think it might be the injectors as the place i had it last week said a injector service is well needed on this high miler.

Will post the results tomorrow.

Thanks

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[Jasondj]

Right, just got word on the fuel pressure test. Next will be the dyno to see the air fuel mixture.

On prime the reading was 2.5bar and idle was 2.1 bar. According to them it must be on prime around 3.3 bar and idle 2.2bar

Is it correct what they are saying?

They say it might be the fuel pressure regulator or the fuel pump but they cant tel me for sure.

I know with my Corsa years back if you remove the vacuum line from the regulator the needle will jump up a little, this meant it was working, does the same principal apply to the AGY motor?


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[panic-mechanic]

The vaccum line reduces thenpressure when the engine is running.
You Should see 3 bar without the engine running and or if it is running and the vacuum line is removed or on full throttle under load you should get 3 bar.
On idle with vaccum line connected around 2.6 bar.
The regulator is 3 bar so you should see 3 bar. Not 3.3 bar unless their calibration is out on the gauge.
A broken or cracked fuel rail can also drop the pressure.
So can a iffy pump,a dirty filter or a cloged intake on the pump.

[Jasondj]

Yeah thats my understanding also. If the regulator is 3 bar it cant go over 3 bar.

But anyway so on idle it must also be 2.6 and prime 3bar. So basically its a little more pump related.

Can it also be why the car cuts out now and then when driving a very steap incline?

Ill get the car back this evening and see what they say, the dyno will only be done past 5.

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[dazza]

Possible it is leaking injector(s), especially if you have rough idle when cold and difficulty stating...similar thing occurred on the MKV Golf and Jetta's in 1.6 engine configurations

[Jasondj]

Funny thing is, and this baffled everyone i talked to. The rough idle when starting the car when it stood over night is only in the summer time and now winter. Winter i have no issue at all.

To test and clean the injectors will cost me around R950, but i can buy a brand new Bosch set from a friend for R1200, think that's a better option maybe, then i know they are clean and correct.

Will see what the results hold this evening on the dyno with the mixture.

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[VAG Fan]

I don't know this type of fuel injection system, but to me it sounds as though the management system is over-fuelling. In winter, this is not such a problem, as there are condensation losses, and extra fuel is needed for starting. In summer, the engine will flood more easily.

Purely intuitively, I would look for any faults on the temperature sensor(s).

[Jasondj]

I did change the coolant temp sensor from a Goldwagen one to Agents unit. Still same issue. There another sensor i missed, MAP sensor thats on the intake?

Hope fully we will see if the car is running lean, rich or perfect on the dyno this evening.

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