Technical Fiat Grande punto 1.2 8v After valves changes 3 and 4 cilinders dosnt work

[Agdesas]

Hi.I changed all 8 valves and now have a problem 3 and 4 cilinder not working...what can be wrong? i check sparks its ok.

 

[bugsymike]

Hi.I changed all 8 valves and now have a problem 3 and 4 cilinder not working...what can be wrong? i check sparks its ok.

If all four spark plugs are working and the fuel is injecting to them all, bearing in mind the engine work just done I would give it a compression test, just to eliminate low compression as a problem.
I assume it wasn't missing on the same two cylinders before.

 

[Agdesas]

If all four spark plugs are working and the fuel is injecting to them all, bearing in mind the engine work just done I would give it a compression test, just to eliminate low compression as a problem.
I assume it wasn't missing on the same two cylinders before.

it was no problems before until i try to change timing belt without timing tool and i lost timing marks and pistons hits valves then i have to change valves and after this i set timing belt with timing tool and now i have this problem...

 

[bugsymike]

it was no problems before until i try to change timing belt without timing tool and i lost timing marks and pistons hits valves then i have to change valves and after this i set timing belt with timing tool and now i have this problem...

I would do a compression test first then. If it is low on those two cylinders it looks like head off again, are they the ones you put new valves in and did you carefully "lap/grind" all the valves in. When not changing all the valves, only the ones that obviously appear damaged, it is a good idea to gentle roll the valves on a flat surface to check no others have got slightly bent, but they all should be lapped in again when head is off.
Another thing to do is carefully look at the tops of all the pistons for marks where the valves have hit.
On diesels with timing failure the conrods get bent as well, showing as two pistons not at matching heights in the bores!
Also that there is no other damage and hydraulic tappets should be left in oil as if they are worn they sometimes take a while to fill up and work correctly which can cause a misfire usually with a loud tapping noise. Another thing is any part not being replaced must go back exactly where it came from. i.e. No.1 Ex. valve in No.1Exhaust valve guide etc.
Future advise you now know is , after any cam belt /chain timing work on an engine always gentle turn the engine over at least two full revolutions by hand, as that would have avoided everything !!!