Just replaced the plugs in my 2011 1.2TSI Yeti and judging by their external appearance it may be their first time out!

 

I believe they are specced for 60,000 miles and with the car recently turned 100,000km (I'm in Spain) if they are originals then they are fractionally over that.

 

In the photo they are L to R 1-2-3-4 and 3 & 4 look considerably weaker than 1& 2, is that normal?

 

 

 

Strange that the 2 with corrosion have been running much weaker than the other 2.
Did you replace them with iridium plugs?

6 hours ago, KiNeL said:

Just replaced the plugs in my 2011 1.2TSI Yeti and judging by their external appearance it may be their first time out!

 

I believe they are specced for 60,000 miles and with the car recently turned 100,000km (I'm in Spain) if they are originals then they are fractionally over that.

 

In the photo they are L to R 1-2-3-4 and 3 & 4 look considerably weaker than 1& 2, is that normal?

 

 

 

Your car has a waste spark ignition system. This fires spark plugs in pairs, 1 and 4, then 2 and 3. Electrically one plug gets a positive sparking voltage, the other in the pair gets a negative sparking voltage so current flows in opposite directions in the two plugs. Because of this, electrode spark erosion wear is greatest at the tip in one plug and at the ground electrode at the other.

The plugs have an iridium alloy tip, which are incredibly tough and suffer very little wear, but the ground electrode has a welded platimum alloy disc, which is less tough, and after a while the disc often becomes detatched and you are down to the steel ground electrode to take the spark errosion.

 

The rusting on the bodies is due to an external problem, water from somewhere. Looks and could be serious, it is not normal. Is the heat shield removed? Looks like a leak from somewhere in the vicinity, as the turbo is water cooled, check for leaks around the stainless pipes that feed water into the turbo.

 

Alternatively it may be just because of their age. 10 yrs is a long time. Maybe you had a period where the car was subjected to lots of water or stood for a long while. Just monitor the replacements.

 

Edited 14 August, 20214 yr by xman

1 hour ago, xman said:

Electrically one plug gets a positive sparking voltage, the other in the pair gets a negative sparking voltage so current flows in opposite directions in the two plugs.

How are the 2 negative sparking plugs isolated from the head with the engine being negative earthed?

36 minutes ago, Urrell said:

How are the 2 negative sparking plugs isolated from the head with the engine being negative earthed?

My understanding is that the HT coil secondary winding for a pair of cylinders is not 'earthed'. One end of the winding is connected to one plug, the other end to another plug, hence those two plugs will be working in opposite polarities.

1 hour ago, Urrell said:

How are the 2 negative sparking plugs isolated from the head with the engine being negative earthed?

 

2 hours ago, xman said:

The rusting on the bodies is due to an external problem, water from somewhere. Looks and could be serious, it is not normal. Is the heat shield removed? Looks like a leak from somewhere in the vicinity, as the turbo is water cooled, check for leaks around the stainless pipes that feed water into the turbo.

 

Alternatively it may be just because of their age. 10 yrs is a long time. Maybe you had a period where the car was subjected to lots of water or stood for a long while. Just monitor the replacements.

 

Heat shields all in place and nothing looks untoward. No evidence of any leaks so more likely the second option, overzealous engine pressure washing perhaps?

 

I have no service history for the car which is why I'm starting with a blank sheet with an oil and filter change and new spark plugs.

 

That said the engine has very clearly been worked on in the past as at the very least there is unmistakable evidence of the head having been off, traces of non OEM gasket goo etc. 

 

It runs perfectly though and is very quiet with just a hint of valve train noise when the bonnet is up, oil consumption over the 1000km or so I've driven it has been zero.

 

For the record I'm an old school amateur enthusiast who and can pull and rebuild an MGB engine or gearbox/overdrive in a weekend with my eyes closed and one arm tied behind my back but not at all ashamed to admit that all this modern witchcraft leaves me a bit nonplussed!

If the sealant looks sloppy around the cam chain covers its likely the chain has been changed, hopefully for the latest full upgrade kit including latest hydraulic tensioner. Very common on early CBZA/CBZC engines.

 

Watch out for loud prolonged machine gun rattles on cold starts, switch off immediately and then try a  restart. Indicates the hydraulic tensioner has backed off and/or chain is stretched. High possibility of the chain jumping on the bottom sprocket or even coming off completely. Early revisions of the chain drive were both poor in design and of poor quality. So a revised design introduced over the course of 2012. More details elsewhere on this forum.

 

A slight rattle that only lasts a second or so is nothing too much to worry about. You get that even with the revised kit, but even then I'm inclined to switch off immediately and restart to allow the chain to align. Usually its nice and quiet on a restart.

 

In any case, avoid forcing the engine backwards, e.g. parking facing uphill in a forward gear. This pulls the return side of the chain into tension and stresses the tensioner which can slip back and even strip the internal ratchet and push it back and the chain goes slack.

 

So if you must park in gear then, if facing uphill, select reverse, or downhill, select first. Hope you understand the reasoning.

 

Another thing to check is whether the small PCV valve (about £16) has broken off. Situated in the back of the camvcover near the right, gearbox end, often found hanging on the rubber hose attached the airbox.

 

Again common on earlier engines and more detail available on this forum.

 

Check the ignition leads all read the same resistance (OE cables in 2011 are 9k ohm), reason being that cable to No.3 plug specifically often goes open circuit due to heat damage but the engine continues to work normally due to sparking internally, however this results in highly elevated voltages at the coil pack which then eventually breaks down.

 

New coil pack and leads are not that expensive (avoiding the dealer) Later engines are fitted with leads that have corrugated sheathing called "marten protection" which also conveniently protect the leads from excessive heat.

 

Otherwise, an excellent engine. (I shan't mention turbo actuators, I don't want to frighten you unnecessarily) 

 

 

2 hours ago, xman said:

 

This fires spark plugs in pairs, 1 and 4, then 2 and 3. Electrically one plug gets a positive sparking voltage, the other in the pair gets a negative sparking voltage so current flows in opposite directions in the two plugs.

That looks like positive going thru both pairs to negative earth  via plug body.

1 hour ago, Urrell said:

That looks like positive going thru both pairs to negative earth  via plug body.

Neither end of the ht coil secondary is connected to earth. When a spark is needed one end of the coil will be positive with respect to the other end (but completely isolated from car's earth) Both plugs will spark, because they are in series with one another. 

 

Bit more info here

 

https://www.ngk.com/wasted-spark-ignition-systems

 

Edited 14 August, 20214 yr by muddyjim

I'll try and explain.

 

Don't get hung up about a "negative earth". The spark plugs are all connected to "chassis" historically mistakenly referred to as "ground" or "earth" which no car actually is connected to.  Chassis is battery zero volts.

 

When one of the transistors shown above closes the circuit (as contact points would do), current builds up in the primary winding and generates a magnetic field in the iron core. When it opens, the current is interrupted and the magnetic field collapses causing a large back emf (voltage spike) to appear at the primary as the magnetic field is looking for a way to release its energy, generating several hundred volts at the transistor collector. This is reflected in the secondary winding which acts as a transformer, multiplying it up to many kV. Because of the secondary circuit configuration, one end of the secondary winding will spike positive and the other negative, both gaps will spark over and current flows only in one direction until the energy stored in the magnetic field is dissipated.

 

So one tip goes very positive, current flowing from tip to ground electrode (which is at chassis potential) and the other tip goes very negative, current flowing from ground electrode (at chassis potential) to tip. To add some confusion, the electrons responsible for the spark plasma, actually flow in the opposite direction to the current, its the flow of electrons out of an electrode that errode it.

 

If you don't believe me, get an oscilliscope and check, but remember we're talking several kV here....

 

Hope that description helps...

 

Some homework

https://www.physicsclassroom.com/class/circuits/Lesson-2/Electric-Current

Edited 14 August, 20214 yr by xman

7 hours ago, xman said:

If the sealant looks sloppy around the cam chain covers its likely the chain has been changed, hopefully for the latest full upgrade kit including latest hydraulic tensioner. Very common on early CBZA/CBZC engines.

It's a CBZB engine and I'm tempted to pull the top chain cover just to see what's in there. Not sure at the moment if it would actually reveal anything useful (is it possible to identify the modified 'anti chain jump' top cover without removal?), but no doubt there are folk here who could tell by photos.

7 hours ago, xman said:

Watch out for loud prolonged machine gun rattles on cold starts, switch off immediately and then try a  restart. Indicates the hydraulic tensioner has backed off and/or chain is stretched. High possibility of the chain jumping on the bottom sprocket or even coming off completely. Early revisions of the chain drive were both poor in design and of poor quality. So a revised design introduced over the course of 2012. More details elsewhere on this forum.

 

A slight rattle that only lasts a second or so is nothing too much to worry about. You get that even with the revised kit, but even then I'm inclined to switch off immediately and restart to allow the chain to align. Usually its nice and quiet on a restart.

Yes I'm aware of the rattle and what it potentially means.

7 hours ago, xman said:

In any case, avoid forcing the engine backwards, e.g. parking facing uphill in a forward gear. This pulls the return side of the chain into tension and stresses the tensioner which can slip back and even strip the internal ratchet and push it back and the chain goes slack.

 

So if you must park in gear then, if facing uphill, select reverse, or downhill, select first. Hope you understand the reasoning.

Had to think about it for a moment but yes, I understand. It's substantially flat hereabouts and I'm not given to parking in gear but will bear this in mind, training 'er indoors might prove more of a challenge!

7 hours ago, xman said:

Another thing to check is whether the small PCV valve (about £16) has broken off. Situated in the back of the cam cover near the right, gearbox end, often found hanging on the rubber hose attached the airbox.

 

Again common on earlier engines and more detail available on this forum.

In place and intact.

7 hours ago, xman said:

Check the ignition leads all read the same resistance (OE cables in 2011 are 9k ohm), reason being that cable to No.3 plug specifically often goes open circuit due to heat damage but the engine continues to work normally due to sparking internally, however this results in highly elevated voltages at the coil pack which then eventually breaks down.

I'll check this morning.

7 hours ago, xman said:

New coil pack and leads are not that expensive (avoiding the dealer) Later engines are fitted with leads that have corrugated sheathing called "marten protection" which also conveniently protect the leads from excessive heat.

 

Otherwise, an excellent engine. (I shan't mention turbo actuators, I don't want to frighten you unnecessarily) 

Best not!

 

Thanks for the detailed post