I just had the spark plugs changed and this popped up less than 24hrs later. Any ideas on quick things I could check?

 

Check each coil pack connection. Basically trace from the spark plug every connection, but for sure the connection to the coil pack on each cylinder.

Do you have a GAP tool? If you do, you can plug that in and run the vehicle and see which cylinder isn't working.

 

Second what chpsk8 said. If you had someone change the spark plugs for you, take the Defender back to them.

 

Check for fault codes first. That may show the problem.

check for misfires and in what cylinder (GAP tool can do both of these things.

There are multiple hoses that need removal and replacement. If any have not been correctly repositioned and clipped in there could be an emissions fault.

there are multiple electrical connectors that need to be removed and reattached. Plenty of room for error in these. Each one a little puzzle unto itself.

Each spark plug and ignition coil need to be carefully repositioned and torqued to spec. More room for error there. Precision is needed.

Aside from stripping the thread on a plug, getting a CEL after changing plugs was my biggest worry as there are so many potential errors that would require hours of labor to resolve.

Straight back to the tech who did the dirty. This is far from a simple task.

 

If the engine is running smoothly, no misfires or issues with driving or accelerating, then it’s very likely that in removing everything to access the plugs and coils he either forgot to replace a a vacuum line or similar or dislodged something in his efforts. A lot has to be removed to get to the plugs, and if it’s not put back correctly that CEL will be the result. Maybe an electrical connector was either not reconnected or was not seated firmly when reassembling everything.

 

@GavinC - Stripping threads on a spark plug is my horrid fear as well! I remember as a kid (back in the last millennia) my dad changed the spark plugs in his Chevy Vega. Yeah, don't ask. The stories around that thing are still entertaining the family. Anyway, back to the "sparkplug incident". He changed the plugs and stripped one. Left it in there until he could take it to a "real mechanic" to repair. Next thing I know, in a loud explosion it launched the spark plug almost thru the hood. One of the most dramatic moments of my youth.

 

Thanks for all your help! It is wild how big of a job this is. Acceleration was fine, light did not come on until the next morning (Sunday). I took it in Monday morning and the tech had not attached a hose all the way. In and out within 20mins with everything functioning as it should. Apparently if the CEL flashes it is detecting a misfire and can get bad quickly.

 

That's great that it was something quick and painless. Easy enough to miss a hose. Probably one of the easy superficial ones on the front air duct.