Poor running, Throttle body and idle 1.4 BBZ

[Inkubate]

Hi All,
I have been looking around this forum for quite a while now trying to diagnose and fix poor idling and misfires on my 1.4 Formula sport. So far I found poor compression on cylinder 3 that has been fixed and a cracked brake servo vacuum pipe thats also fixed but despite these and a throttle body clean and vacuum leak check I'm still getting misfire. Obvious stuff like plugs and coil packs have been changed / swapped but to no avail.

Oddly however when I re-adapt the throttle body in VCDS it goes through the run sequence then settles on around 4.2% and says 'ADP OK' however about 10 seconds later whilst still on 'ADP OK' that value jumps to around 6.8%. Has anyone else seen this or am I likely facing a bad throttle body? The car also only idles once hot around 670rpm and is a manual! Attempting adjustment in VCDS adaptation 01 does nothing what so ever and its set to 158 by default but nothing makes a difference. Oddly as well the misfires are more problematic on very hot sunny days - when its colder it seems more stable although there is still some lumps in the idle.

I really like the car but this chasing faults is starting to wear me out so any advice would be most appreciated as I've looked through these forums extensively but not found these exact symptoms.

Many Thanks,
Chris

[Doctle Odd]

Is the butterfly valve closing fully in the throttle? The plastic gears may be worn and you might need to replace the throttle body. Also check the air intake temperature sensor and the CTS

[Inkubate]

Thanks for your reply. It felt like the butterfly valve closed properly when I cleaned it but am not totally sure. The coolant temperature reading increases steadily to around 90 as expected so would I be correct in assuming that the coolant temp sensor is OK? I may just change the throttle body as I'm guessing the adaptation behaviour I described is not normal?

[Doctle Odd]

Coolant temperature sounds right. Can you get your hands on another throttle body? Yours may have ran it's race

[Inkubate]

Hi Again,
I've looked into this again and have found that my cylinder 3 is still low on compression even after valve work so may still be the issue. The odd thing however is that all cylinders including 3 are well within spec at 225, 225, 195, 220 PSI. Therefore I don't understand why 3 is misfiring as the min spec is 7 bar which this meets at 13.4 bar - the only thing is it being 2 bar lower than the other 3 cylinders. Before I go further can anyone please shed any light on this as it seems confusing.

Many Thanks,
Chris

[Inkubate]

Hi again,
As mentioned earlier I had the exhaust valves replaced on my Ibiza back in April due to misfire and low compression. This failed to fix the problem and the garage denied it would be an issue with the work that they did replacing the valves so wouldn't do anything further. Having some time during the last week I refurbished an old scrap cylinder head and swapped it myself which has now totally fixed the problem. However looking at the condition of the valves and seats that were replaced in April on the old head I would like any opinions please. Pictures are below of the new valves and seats that the garage fitted and I would appreciate any advice as to if this was caused by poor workmanship or something else - 4 months doesn't seem long for them to get like that!

Many thanks for looking.

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