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Discussion Starter #1
I did a rebiuld of the top end of the engine (valves and such) and replaced the plugs with platinum ones. This is a 91 NA and I thought I read or heard somewhere that you shouldn't use platinum plugs on the older models. Anyone have any ideas or heard something similar?

Right now the engine is burning too rich and missing a bit. I don't know if the plugs have anything to do with it or not (maybe there not igniting everything. Comments. Thanks.
 

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I know for Turbo's we're recommended to use cheap NGK 6097 copper plugs gapped at like .28

People generally stay away from fradgile platinum plugs or fancy spark plug wires...
 

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Discussion Starter #3
Think I give the old copper plugs a try (those platinum ones didn't seem too beefy to me - ultra small tipped electrodes). I put new wires on as well (stock) but don't like the way they fit (hard to snap on and a couple of the rubber tips on the plugin end got stuck at the bottom of the tube - crap!!!). Might have to ditch those buggers as well. Thanks for the info.
 

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platinums don't have ultra small tipped electrodes, iridiums do.
you should be fine w/ the platinums. should gap it to spec.- .043" if I remember correctly. you'll definitely have problems if you gap it at .28, whether in mm. or in.
one step colder copper plugs gapped closer than stock(.031" on turbo models) are recommended for Turbo models running higher than stock boost. But only for track use. Daily driving a cold plug at .028" will foul it unless you go wot stop light to stop light.
so, you might wanna check your cam and base ignition timing first.
 

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Discussion Starter #6
I know my timing is off cause I can't get the idle below 1300 (I'm waiting for a used ISC valve a guy is sending me - hope it is better than what I got now - I figure the ISC is bad since it didn't meet the resistance values called for in the manual so it is my first place to try. I can't time the engine right until I get the idle down. I can smell it burning too rich, just thought these plugs might not be helping too much either but it sounds like they should be ok. thanks for the input.
 

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You can't smell it running rich, thats impossible. CO is an odorless gas.
You already mentioned that it's misfiring. If it's constantly missing, then what youre smelling is HC(unburned fuel).
 

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Discussion Starter #8
Running rich has always meant too much fuel in the mixture and not burning all of it. I can smell the unburned/half-burned fuel and yeah, it is HC. Thx for the input nonetheless.
 

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If a vehicle is running excessively rich you'll definitely smell HC in the exhaust. But saying "it's running rich" just bec. you smell HC in the exhaust is silly especially for a car that the owner said is misfiring. Let's just throw away that wideband or that gas analyzer or that scanner tapping for fuel trim. Let's just stick our nose in that exhaust to tune our cars or repair our drivability problem.
What if a car is running closed loop stoic AFR, then a misfire occurs? Is it running rich? I smell HC, so it must be.
 

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Discussion Starter #11
Before this gets too fat out of hand let me clarify some things. I agreed with you OEMonkey that it is HC (ie. hydrocarbons) because that's what unbrunt fuel is and just plan fuel for that matter. I, myeslf, never call it HC but I can agree with you for the sake of arguement.

Second, sometimes a nose is the best sensor there can be. I've done at look of work tinkering with old cars over the years to know what an exhaust smells like for an engine that is not completely burning all the fuel. I did mention that there is some misfiring but it is symptomatic of an engine running too lean a fuel mixture. The Toyota manual actually spells this condition out as " Running too rich, misfiring".

Third, fixing cars always requires a degree of common sense and not always thinking that one needs to rely solely on sophisticated equipment or computers to give them an answer.

There is no need to berate someone who employs these time tested and proven techniques.
 

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I offer quick and easy diagnostic routines and some facts. And I try to illustrate it w/ real world experience and what should be well known facts. I wasn't trying to berate anybody, but understand how it could be misconstrued. I apologize to jtl and hope you get your car rolling healthy soon.
 

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JekylandHyde said:
Lachean, the turbo gap is .028" and it is the Iridiums that break (are fragile).

Platinums are fine for the NAs and mildly modded Turbo MR2s.
Typo.... but way to call me out JH
 
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