Missing on 2 cylinder 4and 6 right beside each other i have done a compression test thats fine new tuneup still does it plugs are fireing but blacking the 2 plug tips what could it be

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Seat (pronounced See-At) is a spanish car manufacturer that make small 3 and 4 cylinder pieces of junk. I don't think they make a straight 6 or V6? ALL questions in this category need 'year make model' as the first 3 words and Fixya software will offer you the correct category. Very often searching 'year make model misfire' will show other occurrences and the the fix for it.

Good testing procedure! Stuck valves only stick open. The rotating cam won't let them stick shut.

Your problem is the spark plug. Replace all of them with OEM spec plugs, normally Champion, NGK or Bosch.

replace the injector in no 2 cylinder

It sounds like your on the right track, the next step is to do a compression test to verify good rings in that particular cylinder.

gas smell is from car not fireing right...mis fire could be coil,plugs or wires and let me ask you is car just missing and if so try tuneup first

possibly wiring harness fault,sesor wheel installed backwards or an even fire/odd fire engine mismatched components

first do a cylinder compression test on engine to verify good engine compression this should be around 110psi to 175 psi check for vacuum leak, intake port for #6 cylindermay be leaking air, or also check coil for that cylinder, if wire and spark plug have already been changed, last replace fuel injector for that cylinder.

Have a compression test done ,and look for a vacuum leak near the cylinder,like a vacuum hose or intake gasket.If the compression test shows a fluctuation between the 3 and 4 cylinder,then the head gasket would need to be replaced.

Recheck the firing order; 1-6-5-4-3-2

On the distributor passenger side radiator to fire wall. 2-4-6-coil
On the distributor drivers side radiator to fire wall. 3-1-5

Cylinder passenger side radiator to fire wall. 2-4-6
Cylinder drivers side radiator to fire wall. 1-3-5

Good luck and also check the distributor cap again for proper seating.

The plugs shouldnt matter they are the same just different manufacturer.

Have you distributor module checked out.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

Check timing belt,sounds like belt may have skipped.