Tony DeCicco

I just changed the plugs from Bosch Super to Bosch Platinum, maintaining the same .028 gap. While the engine is smooth at high rpm, the idle is rocky and low at about 550 to 600. Does anyone know the proper gap for platinums?

Thanks,
Tony

83 911SC

lagoon

Same gap as standard plugs. Your idle should be 900 rpm. 81'SC

Tony DeCicco

Thanks. I checked the plug caps and all was fine. After driving for several hours, the idle has settled but is still at about 700. Can the idle be adjusted at the throttle body or is it adjusted via fuel mixture? It's an 83' ...

Tony

lagoon

It is adjusted at the throttle body with the bypass screw ccw to raise idle speed. 81'SC

Tom F

FWIW, I tried the platinum plugs in my '83 SC years ago, and they made the car run worse. I'd stick with the standard plugs. Have you compared fuel mileage with the two kinds of plugs?

david914

I'll cast my vote for "standard plugs" versus platinums. I haven't had much luck in either of my cars with the platinums. Good ole' copper seems to work best, plus they're alot cheaper! <img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" />

Tony DeCicco

This is what I found... see if it makes sense to all (btw, my handle changed to my name from 964newbie...)

I kept the old plugs and measured the gap on each. They were all above .040 inches and worn. The idle adjuster was in quite a bit as well. I read somewhere that bigger gap = faster idle. I adjusted the idle and brought it to 900 rpm. While the acceration is smooth, the performace is not noticibly different than the "Super" plugs. I also noticed that the throttle response is not as crisp. At next tuneup, I may very well go back.

Thanks to all for your help.

Jdub

A sloppy idle can also be tight valves. You should check the valves, loosen up the advance mechanism in the dist. with a good out-of-car cleaning, and then work from there.

Jw