Asta La Vista

Plugs look normal. Read them at the electrode (cylinder) end.

Plugs can be misleading depending on how you "chopped" the engine.

I know on my motorcycle, the procedure is to run the engine to operating temperature, get on a highway run at speed. Hit the KILL switch and pull the bike into neutral, coast to a stop. Pull plugs for the read. This procedure captures the burn on the plugs at engine load, temperature and speed. But, my bike is N/A with a a pair of carburetors.

I'm not sure if the same or similar procedure applies to these engines.

 

these days, for the most part, fuel trims are the quickest/ easiest way to tell if there is a fuel control problem.

If the system was lean enough to damage or show excess heat on a plug it would be reflected in the trims. If the system was rich enough to soak a plug with fuel it would be reflected in the trims

Thats not a knock on plug reading, it has its uses in certain situations. Before the convenience of OBD it was a very helpful window into the health of the engine. Its just these days, if you know how to read and interpret data, you have tons more info sitting in your lap on a screen while you drive down the road.

Its less intrusive into the motor too, sometimes plugs and coil packs are buried and hard to get to. Why turn bolts if you don't have to?

If a customer comes in complaining about mpgs, I'm looking at thermostat operation (want to see coolant temp get hot quickly and stay there) and fuel trims.

If the trims are stable and the engine isn't running around cold.. look somewhere else..