I have a Miata. I have a plug that is stuck. Prob been in the car 20 years/95k miles. It turns about 1.5 of a turn then stops. I am afraid to just push it and snap the thing off in the head. I have put penetrating oil down the plug hole (not pb blaster). Any suggestion on how to get this out and not F up anything? Any tricks?
You could try some heat, but I believe the Miata has an aluminum head, so you’d need to be careful with it. It sounds like it’s galling as you’re turning it. I hope heat works because the alternative won’t be easy or pretty.
If it has any threads exposed in combustion chamber, it probably is carboned up. I would do some type of top engine clean. Screw the plug back in, do the seafoam cleaner or similar, and then try removing the plug again. If it still won't come out, try the cleaner again. If you try to force it out, you'll probably strip it and then you'll need to do a helicoil repair. Hell, if it had a carb, I would tell you to start it up, get the rpms up a little, then dribble a cup or two of water down the carb and steam clean the cyls. Old trick...
I’ve run into a similar situation. Liquid Wrench, PB Blaster or your favorite penetrant of choice, spray the outside of the plug, back it out until it stops, spray again, tighten it back up... rinse and repeat. It’ll work itself out with repetition (and lubrication).
I had a similar problem many years ago with a 710 Datsun. I just kept turning the plugs back & forth and eventually I git all 4 removed with no damage.
The easiest solution- if it's not misfiring tighten it back up and move on with your life. I did this with a Beretta I drove in college. It had 140k on it so I figured I owed it plugs and wires. Two of the back plugs were doing the same thing. I could tell i was pulling the threads out of the crappy alluminum castings. I punted and drove the car another 2-3 years with 4 new plugs and 2 old ones. Also- you may consider not broadcasting to the world that you own a miata!!
This is my 3rd Miata through the years. I love them. Great driving cars. You won't outrun anyone going down the road but drive it through the turns and the like and it will beat most any car every time to the other side. Then there is collectable side of things. First gen (pop up headlights) units are selling like hot cakes if you can get one in good shape. The special edition units with low miles are clearing 15 to 20k now. Well anyway, this plug is driving me nuts, I want it out. ha ha ha ha.
Just got home and went and started on the plug. It came up and gave me a little push back for a second then came out fine. The threads on the plug were fine, just the last 4 or so were browner then the others. I assume carbon and that was what was holding me up as the plug came out? Tune up done now.
Fat girls, mopeds and Miatas.. Good to see you got it out. Alluminum heads can be sketchy for this reason.
Mine was a 90 or a 91. My sister and I shared it in college. It had a 3.1 and an auto trans. It was a plain jane car but it ran well and made good power for what it was. I think it was 900 bucks and we drove it for 5-6 yrs. I think it had 170k on it when we were done. It was a good rig.
Yea it has good power, I would have loved to have had a manual version. I had this... https://barnfinds.com/1990-chevrolet-beretta-indy-pace-car/
That's a lot of yellow. I had friend in highschool with an earlier Beretta with a 2.8 that was a 5 speed. It was a hoop by the time he got it. He cut the steering wheel so it was the same shape as the batmobile. It was a wild time.
