New plugs and wires done last night. Anyone know what causes the yellowing of the plugs 1 & 2? My stumble upon acceleration is gone. The wires were original (10yrs old). All parts ordered from 1stsubaruparts.com.

 

97 OBW 2.5 dohc, 110,000 miles.

 

 

 

click to enlarge

I believe it has to do with the fuel air mixture. A slight yellowing of the insulator reflects an ideal fuel/air mixture, whereas a white (hot) insulator reflects a lean fuel/air mixture.

 

Most cars these days are tuned to run pretty lean to meet EPA standards.

do you remember if the yellows were front, rear, left or right????

 

New plugs and wires done last night. Anyone know what causes the yellowing of the insulator on plugs 1 & 2?

 

97 OBW 2.5 dohc, 110,000 miles.

 

 

 

click to enlarge

Yes, cylinders 1 & 2. The front ones.

 

rd

New plugs and wires done last night. Anyone know what causes the yellowing of the insulator on plugs 1 & 2?

 

97 OBW 2.5 dohc, 110,000 miles.

 

 

 

click to enlarge

 

I think the porcelain on those two plugs may be yellowed because of engine oil seepage around the "spark plug opening" gaskets in the cam cover. Was there any engine oil on the spark plug wire boots where they pass thru the cam cover and attach to the plugs?

Was there any engine oil on the spark plug wire boots where they pass thru the cam cover and attach to the plugs?

 

Not that I noticed, although my engine has all the usual seeps. I'll address those now that my hesitation seems to be gone.

Good question, johnceggleston. The rear plugs may be baked white because the rear two cylinders run hotter than the front cyinders (1&2), which get more air flow. A leaner fuel/air mixture will also cause the engine to run hotter.

 

So long as the insulator is not fouled by oil or a rich fuel/air mixture (black soot), a slight yellowing (the color of a coffee stain) of the insulator is completely normal.

The yellowing he is referring to is outsided the combustion chamber. I can't see mixture being able to affect this portion of the insulator. If it can, I would expect to see effects on the pistons shortly.....

 

These are the front plugs. Could it be road crap getting cooked on? Or some minor oil leak from the front of the engine, getting blown back onto these plugs?

 

Rob.

The yellowing he is referring to is outsided the combustion chamber. I can't see mixture being able to affect this portion of the insulator. If it can, I would expect to see effects on the pistons shortly.....

 

These are the front plugs. Could it be road crap getting cooked on? Or some minor oil leak from the front of the engine, getting blown back onto these plugs?

 

Rob.

 

Ah, thanks for pointing that out. What you say makes total sense then.

How hard was it to do the plugs, and what are the recommended parts in the process. It looks a little tight. I have a 99 OB and all the literature I have been able to find stops at 98 and starts again at 00.

Thanks,

Billy

It is tight. But very doable. Remove washer tank and air intake pieces for improved access.

 

Do a search for specifics on the tools.

 

Actually give me a few hours and I'll post a pic of my tool setup.

 

rd

The yellowing actually comes from the ionization of oil in the presence of sparking voltage. It's normal but a lot of build and and debris can lead to spark leakage if you couple that with bad boots.

 

I would be more concerned with what else is on the insulator. It looks very serious and I am surprised no one pointed it out yet... THEY SAY BOSCH PLATINUM!!!! I know they are cheap for a platinum plug, and you will get what you pay for...

 

I just replaced my OE NGK Platinums with a projected tip spark plug (slightly colder too), and have a noticeable increase in mileage. Stick with NGKs, I think you will be happier.

 

Just my $0.02

Well I tried but I suck with computers, so give me your email and I'll send the photo of the tools.