Spark Plug Assessment

vesnyder · vesnyder's Garage

Attached is a plug I just removed from my rebuilt motor - about 600 miles - and my milage is horrendous. Any ideas?

DRACO A5OG · DRACO A5OG's Garage

Hmm Looks Good. my 2 cents.

What is Guage setting, Base Idle Settings and Air/Fuel Mixture?

Steve@Rennsport · 05-23-2008, 02:01 PM

Vance,

If that plug came out of your engine while it had idled for a moment, the coloration and condition are largely useless,....

The only way to "see" what is going on in the engine is by performing a "Plug Cut". This is done by holding the engine at a specified throttle setting and load for 20 seconds and then quickly switching off the ignition. Then,.....the plug coloration is meaningful to someone who knows what to look for,...

Now,..if your fuel consumption is higher than normal, I would ask if you had your injectors tested and cleaned? Have you checked & confirmed your CIS control and system pressures, both hot and cold?

vesnyder · vesnyder's Garage

I let the car warm up then took the car out on the freeway at 70 MPH. Got off an exit and shut it off as I was exiting. Took the plug out right there and took this pic - does that help?

BTW - It is a carbed car.

JFairman · 05-24-2008, 08:28 AM

Looks like a high heat range "hot" plug in an engine thats running very rich AFR's.

Steve@Rennsport · 05-24-2008, 08:44 AM

Quote:

Originally Posted by vesnyder

I let the car warm up then took the car out on the freeway at 70 MPH. Got off an exit and shut it off as I was exiting. Took the plug out right there and took this pic - does that help?

BTW - It is a carbed car.

If you backed out of the throttle before you cut the ignition, the "Plug Cut" won't tell you anything.

Without all the details about your engine such as displacement, compression ratio, camshafts, intake specs and jetting, spark plug heat range, ignition, header/heat exchangers, & muffler, its difficult if not impossible to offer anything constructive.

Complete information is really essential when attempting to diagnose something from afar,...

Henry Schmidt · Henry Schmidt's Garage

Come on Steve, it's shouldn't be that hard for a master like you. Just read the tea leafs or your crystal ball. It's just a plug after all.