Another Spark Plug Question...

[cbeaudry]

My 91Q has about 135,000 miles on it now. I bought it when it had 90,000. When idling, the engine kinda "rumbles" along making the whole thing shake. I figured that it's probably the spark plugs that need to be changed.

When I went to autozone (yes, I am a rookie...), they listed the Danso double-platinum plugs as the OEM part in stock. From reading these boards, I see that the NGK's are the OEM.

Are Danso the same but are marketed with a different name or is Auto Zone screwed up by listing those as the OEM parts? If they are, should I return them and buy the NGK's somewhere else?

Two other questions:

First, I do mostly city driving but do occasional highway driving. I never go more than 75-80mph on highways. If I need to get the NGK's, do I get the hot or cold plugs for my driving conditions in St. Louis.

Second, is this something I should leave to a mechanic? I looked in the service manual and changing plugs seems to require the disconnecting of several things and disassembly of the engine's cover. As a newbie, would this be over my head?

Thanks for the help. I wondered where everyone on the Yahoo boards had disappeared to...

Charles.

[cbeaudry]

The Denso (not Danso as I previously put in there) plugs they sold me were plug # PK20R11 which were listed on the Denso site as the plug for the 91Q.

[nisstech]

The direct cross for the ngk to denso is the pk20r11, most of the guy's here prefer to use ngk, I have found that bouth are a good spark plug. PK20 is equiv to the "6" ngk heat range and the pk16 is equiv to the "5" ngk. The denso is a oem for toyota/lexus. On some of our cars mostly the ls430,sc300 and sc400 we mostly find ngk's in from the factory. I'am running the pk16's in my 92'q45 and find them equal to the ngk's in every way! Fast start's ,very smooth accl and very stable idle. It seem to be a matter of "what you like" Or a little brain washing from the few with nothing more than "it's what HE uses" Stay away from the champion,autolite,splitfire and mighty cheap plugs. NGK and Denso are the two best plugs and only plugs to be used in you engine. As for heat range there a a few great trends on this to be found here or visit NGK and Denso's web address for more info on this.

[forecast]

For times to change plugs, see my post at:

http://www.nissaninfiniticlub....21142

While you have the air duct off, scrub the TB. Get shop rags and carb cleaner. Go to town but make sure none of the carb cleaner drips on the rocker cover.

I don't know anything about Denso - everyone here will say "take them back to Autozone and contact Infinitipartsusa.com to get NGK"

If I could be so bold, check my post on my experience with NGK at:

http://www.nissaninfiniticlub....21717

I doubt however that spark plugs will fix 100% of the idle tremor. It could be:

igition system (spark plug, spark power or timing)dirty or broken injectorsdirty TBdirty Plenum

if the spark plugs don't quiet the shakes, I'd suggest you swallow hard and go pay $125 for a tech to do the BG rail flush and plenum scrub. Q45tech suggests making this an annual habit:

http://www.nissaninfiniticlub....21672

dan