Corsa is missing when is warm

[Hoffnungsloss]

Corsa B GSI 16V,
is not running well when warm - shaking and not taking gas.

Symptoms.

Car runs fine when first started but as soon as it starts to warm up it starts to miss on cylinder 4. Spark plug in cylinder 4 shows black deposit within short period of time and appears wet when removed.

Computer connection first not possible - then suddenly established by using C16XE code when engine is listed as X16XE according to Vin number. No explanation of why it will not connect with X16XE code



Checks run.

1) Compression test- very good- no head gasket leak/O ring/valve seat problems?

2) Test for exhaust gases in water system- negative- no head gasket leak?

3) Test for pressure drop in water system with and without engine running- negative-no head gasket leak?

4) Test of injectors- all excellent ( 93% -100% flow through for all units)

5) Test of temp sensor- good

6) Test of Oxygen sensor-good

7) Test of EGR- good but now blanked off until cause of problem found.

Timing belt position checked- correct

9) Ignition coil checked - excellent

Other changes made.

1) New sparkplugs

2) New HT leads between plugs and coil.



Any idea what it could be? Spend lot money and still have not a perfect car running.
Thanks

[LesterPiglet1]

Have you tried cleaning the ICV? This deals with cold starting and if sticking could cause the problems you describe.

[skidmarks]

I had a similar problem with an old Cav.

Does it use a small amount of water? Does it steam slightly when warm and on idle?

I had a tiny crack in the head that was only apparent when the head had warmed up and expanded sufficently to allow a small quantity of water into the cylinder, thus causing juddering but not to the extent that it became a missfire.