981 Boxster S Missfire Mystery

[pec996]

Hoping someone on here can help...

981 Boxster S (late 2012 car) has a misfire on 1/2/3 and computer says thats all it is.

Only happens between 800-1200 rpm and gets worse when warm.

Coils and plugs have been changed.

Leak down is good at less than 3%.

Earth has been checked and replaced.

No borescoring.

In short its nothing mechanical although we are doing a smoke test on the manifold just to be sure but given rev range its highly unlikely this is the culprit.

Any advice or guidance much appreciated as its a head scratcher...

[Magnum 475]

Well, if you've got compression, and you've got spark, that would suggest fuelling issues. One or more injectors not squirting quite correctly / part blocked?

[David W.]

Had a misfire on a 14 reg 991 S, it was a solenoid that does something to the valve timing! They found this when doing other service work. Sorry not to be upon the tech here but my independent had a couple of others needing same repair and parts were on back order. I hadn’t detected it but car (fairly new to me) did seem a bit sluggish at lower revs.
HTHs

[pec996]

Magnum 475 said:

Well, if you've got compression, and you've got spark, that would suggest fuelling issues. One or more injectors not squirting quite correctly / part blocked?

Thanks, I should have said that the computer will show if its an injector, apparently Porsche diagnostics very good

[pec996]

David W. said:

Had a misfire on a 14 reg 991 S, it was a solenoid that does something to the valve timing! They found this when doing other service work. Sorry not to be upon the tech here but my independent had a couple of others needing same repair and parts were on back order. I hadn’t detected it but car (fairly new to me) did seem a bit sluggish at lower revs.
HTHs

Thanks a great help David, thank you

[Pope]

+1 valve lift solenoid; very common on 9x1 cars, can be related to oil filter condition or following a service after filter replacement.