I'm trying to tune my ecm and I pulled a plug to see if its running rich or lean and I pulled this... I have looked at many pictures of plugs but haven't seen this yet. I'm thinking it running lean. But what does the dark spot under the arm thing mean?? My plugs only have about 500 miles on them.

 

Looks glazed, probably running lean.

 

yeah I have high BLM's they are about 140 idle and 137 cruising. I know 128 is what I need to get. At start up it smells like gas though. So I don't know if I need to increase the injector constant or lower it, Or mess with the MAF tables. But these are questions that should be posted in the DIY prom forum...

Thanks for the response. But I got one more question, Why is their a brownish spot under the arm thing I think its called the ground electrode??

 

The surface coating of the insulator looks melted. It's caused by high temperatures IE running lean and racing the engine. Some suggestions if you couldn't correct it via PROM tuning might be to go with a colder plug, taking out some timing, etc.

You should replace all the plugs that look like that too, they'll probably cause misfiring. It's possible you're running rich at idle (looks like it from the ground electrode being black) but lean at WOT so you're getting some deposits from running rich and they're heating up under lean conditions.

 

Wow you know how to read plugs, all I could see it was maybe running lean... but you saw a whole lot more than me!

Timing is set to stock. I'm still learning prom tunning so it's far from being tunned. So for the idle I need to change the MAF tables (I think...), Could I do the same to help the driving around richness? I tried setting the injector constant to 19.7 and that really richened it up for driving around, BLM's where around 125. I think if I set it to 20.5 maybe I'll have 128 for driving around. For the idle do you know if I need to increase the grams or or decrease?

 

I just installed a heated o2 sensor and that really smoothed out the idle but I deffenanty feel a missfire at idle now. I think that might be why it smells rich at idle. I wanted to get it tuned before I changed the plugs but it seems like I need to do it before tuning... anyways this time im getting delco plugs and thanks for the help. I hope my next plugs last alot longer!

P.S. I forgot to ask my question... How long does it take to get a lean or rich reading on the spark plug?