Spiffer

I used to have a problem with erratic idling when warm (engine wanted to die at traffic lights, bouncing between 900 and 500 rpm). I solved that problem by replacing the accelerator pedal with a second-hand one in February, as well as replacing a cracked brake servo pipe before that, along with a set of new spark plugs. Being somewhat alert to idling now, I have noticed an odd phenomenon. When cold starting in cold weather the engine immediately idles at 900 rpm, but cold starting in warm, summer weather (i.e., ambient temp of >20C) the engine idles at 1100 rpm, before dropping down to 850 rpm after a minute, when the coolant reaches aroud 45 deg C, as one expects. I would have expected the same behaviour in cold conditions (but to have a high idle for longer). I suspected a temperamental cooling sensor/connection, but the OBD diagnostics reveal it works in both scenarios. It isn't a problem (yet) but an explanation would put my mind at ease. Is this normal behaviour? Any advice/comments gratefully received.

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.

Job done and problem fixed. The seal had perished beyond belief, which explains the Niagara Falls effect over the entire width of the bulkhead. The grommet/seal for the main cable was challenging and required several more attempts after I'd reinstalled the metal panel, as water was going down the middle of it too, which I hadn't anticipated. I used Wynn's Black Instant Gasket Maker Silicone. Cleaning off the old cruddy seal was a challenge though. As requested, photos attached of the Mk II ...

I'll aim to get some photos. Incidentally, I'm planning to use silicone sealant (like Granville's). What did you use? And did you dispense with the neoprene seal?

I was just about to say the same, from those very good photos.

Thanks, both. Drainage is fine both sides. I think you've identified the problem as the neoprene seal. I've just checked again. The instant I pour water at the wiper spindle it pours down and out between the water box and the metal bulkhead. Not sure why it's so bad, to be honest!

Is it normal for water to pour down the scuttle panel and bulkhead within the engine bay? There's no water ingress to the cabin (so far). I gently tested with a water hose around the wiper spindles (bonnet open). The water isn't lapping over the edge of the seal to the bonnet; it seems just to go straight down past the wiper motor and emerge behind the sound-dampening felt and over the brake and clutch pipes and servo. Not sure if there's something adrift there or if it's designed that way.

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.

That's good to know.

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.

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.

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).

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.

Many thanks to you both -- and also to Pete. It appears my model should have a 60Ah battery, 50% more than the 40Ah than is currently installed, which explains a lot. The 'options' label decoder is very handy too. Thanks for that. T.

Just wondered whether anyone knows what the original battery specifications are for my Fabia. I can't seem to find them, and the current battery fitted by the previous owner is a rather sad aftermarket job at 40Ahr 360 CCA which isn't holding its charge. My trips are mostly short city drives, with a motorway drive once every two months. I'm reluctant to get a battery with an Ahr capacity that exceeds the OEM battery by too much, as I understand that batteries are originally selected with the current output of the alternator in mind, which in my Fabia's case is 70 Amp (larger engines with larger batteries have higher output alternators). Alternators that have to work too hard may overheat, or so I understand.