Spark plug change and check engine light
 

Just changed spark plugs on my 996. After much swearing and extreme body contortions, only to find engine runs rough and check engine light pops up to confirm something is amiss. I think that the problem lies with the coils. Either there is a connection problem with the clips, or one or more of the coils is faulty. I plan to recheck connections, or is installing a new coil pack recommended? Thanks

Check the plugs where the harness plugs into the coils, one or more are not seated.

If you have an OBD reader or Durametric, you may be able to shorten the search for which position it is, by learning the "Pxxxx" misfire code.

Did you check if the coil packs were cracked? This is very common. When you removed the coils you may have sent them to the grave.

Thanks for your response. I rechecked the coils and found one that was not connected, as the rubber boot was folding under. All is well.