Spark plug electrode gap for Fabia 2 1.2 HTP 70 (engine BZG)

[Spiffer]

I wonder if someone could point me in the right direction for finding the correct electrode gap for the above. Haynes manual says 9 mm (NGK plugs), but I'd like to be sure (Haynes isn't the most reliable source of technical information, in my experience, and I've seen 0.6 - 0.8 mm mentioned on this forum - but never 0.9 - which adds to the confusion). NGK's plugfinder just states the plug gaps are preset. Workshop manuals I have access to don't appear to mention this minor detail.

 

The plugs I've ordered are ZFR6T-11G (5960), which I believe are stock replacements.

 

The reason I'm changing them, incidentally, is that the revs are dropping at idling when the engine is hot. I've already replaced a cracked brake vacuum booster pipe, so I thought I'd try the plugs next, as they were last changed in 2016 (9,000 miles ago). If new plugs don't fix it then it's probably garage time.

[sepulchrave]

The plugs come pre-gapped so you don't need to touch 'em.

Incidentally it's the coil energy that dictates plug gap, nothing to do with the plug itself.

[nta16]

Sorry I've no idea of the gap you need but it used to be with NGK plugs that the end number was the preset gap, I assume but don't know that this is still the case, if so then 11 would be 1.1 mm gap.  All databases have errors and omissions and I've found this includes Haynes publications sometimes.

 

ETA: I always check the gap in case the plug has ben dropped or swapped and always buy from a reliable source to avoid cheap fakes.

 

  

Edited 30 April, 2023 by nta16
ETA:

[Jocko]

16 hours ago, Spiffer said:

The plugs I've ordered are ZFR6T-11G (5960), which I believe are stock replacements.

If these are in fact the recommended plugs for the car then the gap is 1.1 mm.

[sepulchrave]

34 minutes ago, nta16 said:

Sorry I've no idea of the gap you need but it used to be with NGK plugs that the end number was the preset gap, I assume but don't know that this is still the case, if so then 11 would be 1.1 mm gap.  All databases have errors and omissions and I've found this includes Haynes publications sometimes.

 

ETA: I always check the gap in case the plug has ben dropped or swapped and always buy from a reliable source to avoid cheap fakes.

 

This isn't possible any more since the plug electrode is protected by a plastic tube to prevent any such variations.

By all means continue with your mediaeval rituals if they bring you comfort but it really isn't necessary any more.

[Spiffer]

23 minutes ago, Jocko said:

If these are in fact the recommended plugs for the car then the gap is 1.1 mm.

I've checked NGK's plug codes and you are correct. And the Haynes manual is inaccurate — or is it? Presumably Haynes got their information from Skoda technical documents (which I can't find to verify). Odd that Haynes would quote a plug with a set gap and then state a different measurement, unless somewhere down the line it was decided to reduce the gap, for whatever reason (e.g., preserve coil pack life).

 

 

[Breezy_Pete]

For the mk1 HTPs the gaps are different for different plug manufacturers,  what's listed for mk2, did you say somewhere?

 

Sorry,  yes, you did  in the first post. What gap did they arrive with?

Edited 30 April, 2023 by Breezy_Pete
All sorts of typing issues!

[Breezy_Pete]

FWIW I can't see any gaps listed in the erWin Fabia mk2 workshop manuals (maintenance nor engine-specific) so Haynes probably just carried forward their info from the mk1 manual when they couldn't find anything else to write.

 

Do you happen to know what your fuel pressure is regulated at? May be stamped into the end of the filter just in front of offside rear wheel.  

I recently discovered that some of the later mk1 HTPs (some if not all BME 12V engines) got 4 bar regs instead of the original 3 bar. May also be true of the BZG. Could be relevant to spark gaps, I guess?

 

Edited 30 April, 2023 by Breezy_Pete

[Spiffer]

2 minutes ago, Breezy_Pete said:

For the mk1 HTPs the gaps are different for plug different manufacturers,  what's listed for mk2, did you say somewhere?

 

The plot thickens. Digging deeper, NGK's recommendations indicate there may be two type for engines with the BZG code: ZFR5P-G and ZFR6T-11G

I note the different heat ratings, and the lack of gap info in the code for the former plug.

 

(BTW, I presume mine is a mk 2, but now I'm not so sure. First registered July 2007.)

 

 

P.S. I can't get to my fuel filter right now to check BAR as the car's parked in a main road.

[Breezy_Pete]

Message me your VIN and I can check it for you.

[Spiffer]

52 minutes ago, Breezy_Pete said:

For the mk1 HTPs the gaps are different for different plug manufacturers,  what's listed for mk2, did you say somewhere?

 

Sorry,  yes, you did  in the first post. What gap did they arrive with?

Haven't arrived yet (Car Parts 4 Less - order a week ago!).

I assume they'll be 1.1 mm, as per suffix code 11G.

Edited 30 April, 2023 by Spiffer

[Ootohere]

It is just so simple with new plugs to check all 3 or 4 are correctly gaped.

Yes they have a cardboard or plastic cover. 

 

Yet even those can have been looked at at a factors or a sellers and the cover off, dropped on the counter by professionals and non professionals.

 

Too often when a car is misfiring and it is suggested that the gap is checked that the person has no idea even if they fitted them.

They might get knocked before they ever get threaded and into the plug hole but then that has always been the case, plenty handless techs, mechanics or DIY,ers about.

 

Lots of issues with cars are those servicing them ignoring things that as apprentices they were taught was the basics, or maybe they are never actually taught much because seemingly someone else can be trusted to have done something. 

Edited 30 April, 2023 by toot

[Breezy_Pete]

Don't think mk1s ever had the BZG engine, so mk2.

[Spiffer]

Just now, Breezy_Pete said:

Don't think mk1s ever had the BZG engine, so mk2.

That's good to know.

[sepulchrave]

18 hours ago, Spiffer said:

...so I thought I'd try the plugs next, as they were last changed in 2016 (9,000 miles ago).

 

You don't even need to change the plugs, at 9k they'll still be like new, it's physical wear, not age that dictates changing them.

 

[nta16]

2 hours ago, sepulchrave said:

This isn't possible any more since the plug electrode is protected by a plastic tube to prevent any such variations.

By all means continue with your mediaeval rituals if they bring you comfort but it really isn't necessary any more.

Oh, to live in a perfect and absolute world, and where age and environment have no effects, I hope it always remains so for you. 

 

[Spiffer]

2 minutes ago, sepulchrave said:

 

You don't even need to change the plugs, at 9k they'll still be like new, it's physical wear, not age that dictates changing them.

 

I wouldn't say like new, given that they're a third way through their lifetime (at least). Bear in mind that Skoda recommends changing them every four years, and the previous owners ran up mileage with short trips over the past 7 years. As I said, I'm having trouble with rough idling when the engine is hot, and plugs are one of the known culprits. If they're coming out for inspection, I may as well fit new ones — with the correct heat rating and correctly gapped; for all I know the previous owner/garage had got it wrong.

[Spiffer]

A tardy update to my original post. I asked my local garage who interrogated Autodata, and the recommended gap for my Fabia 2 (2007-8, BZG) using ZFR5G-P plugs is 1.0 to1.1 mm. So Haynes, at 0.9mm, is wrong by between 10–18%, and would result in a weaker spark and poorer efficiency. The preset gap of this plug is also 0.9, so needs to be widened with the appropriate tool.

Edited 21 October, 2023 by Spiffer