Spark plugs

mazda
miata

#1

Hello,



I just removed all of my spark plugs and one out of four had oil all over the boot cable and outside of the spark plug. Two questions. What do you think is the problem and should I install all of the new plugs and cables or wait for my mechanic to look at the troubled plug or all of them? Thanks for your time


#2

Usually, that’s a symptom of valve cover gasket leaks. Oil does degrade the spark-plug boots. I would replace the gasket(s) and the cables. If you’re going to get someone else to do it, and you have already removed the old plugs, you might as well go ahead and put the new plugs in. I wouldn’t put the new cables in until the VCG(s) are replaced.


#3

I was thinking exactly the same thing as tardis. Just FYI, the torque on valve cover bolts is really low - they often just jiggle loose a little bit. I don’t know how easy the procedure is on this car for full replacement but before doing anything drastic just snug those valve cover bolts down. (This has worked for me before on exactly the thing you describe).


#4

Most likely the o-rings in the spark plug tubes are leaking. The o-rings are part of the valve cover gasket set. I’d install a new gasket set before installing the new plugs and wires.


#5

Hi,

Thanks so much. I think I tightened the valve cover bolts. Are they the little ones on top of the engine(all sides and two in the middle). sorry I’m new at this. Unfortunately I did not read this before I tighten the bolts and I believe I might have stripped one. Is that a problem? Thanks again for your help.


#6

Thanks so much for your input


#7

I agree with the spark plug tube post and agree that they should be changed along with the valve cover gasket. The gasket can take a “set” over time and lose much of the compression that enables it to seal. If you compare the thinkness of the old gasket once removed you’ll find it much thinner than the new gasket out of the package.

Be wary when torquing the valvecover bolts. Some use shoulder bolts and you don’t want to snap those. A friend’s Justy had shoulder bolts. Fortunately, I knew enough not to keep turning when they stopped…