Hey mates

This past evening I changed the plugs out in my Z as she was running oddly rich and rough. This is what I found. Can someone elaborate on why my plugs are orange? They are a bit cooler (5 on the heat range) but I'm wondering.

Thanks

Jan

Edited August 27, 201311 yr by Pomorza

I used a fuel injector cleaner and had orange deposits on my plugs from it... looks like you may have a bad batch of gas with too much refinery additives. octane boosters can do this too....they also deposit on O2 sensors (on cars with those).

Other then the orange coating, those plugs look good. Why do you think you are running rich? I also see you are running BPR5ES-II instead of the BPR8ED-II. Was this to mask a rich condition?

Edited August 27, 201311 yr by Gary in NJ

I also run BPR5ES-II and I was under the impression that they are the hotter plug, not cooler - 6ES is usually preferred.

To answer above questions

I was experimenting to see if a hotter plug would make a difference in my Z. I ran the BPR5ES's for about nine months ago to see if there would be a noticable difference in how the car acted and drove. As for running rich, I have an air/fuel ratio gauge in my Z - in the place of the clock - and during idle it would sit at 11.4 when cold and 12.2 when warm. I don't like it that rich as its bad for too many things - my cat especially. I figured that it was due to the orange deposits on the plugs.

Thanks

Jan

As Virto says, -5 is hotter than the -6 standard. The heat range will only affect how clean the electrode and insulator are, not the air-fuel ratio. Usually hotter is chosen for engines that might have lots of short trips where the engine doesn't warm up completely. The orange deposit, from what I've read, is just residue from additives in the gasoline.

You can adjust your idle air-fuel ratio by opening up (CCW) the idle air screw on the side of the AFM. It will let more air past the AFM vane and lean out the mixture.

Chilton's says, "A small deposit of light tan or grey material (or rust red with unleaded fuel) on a spark plug that has been used for any period of time is to be considered normal."