Cuba

Today I finally got round to changing the air filter and spark plugs on my '94 3vze. Haven't had it long. Air filter was pretty shocking to say the least.





But check out this plug. I have a feeling these things have been in for quite some time. One was really tight for almost half way out. You can see in the thread where it has gummed up. What do you think has been happening to create this condition?



On the bright side, the difference in performance is remarkable. Gained 5-10hp I reckon. Now it's just slow instead of freakin embarrassing.

suncomb1

The plug condition indicates a lean condition / too hot. Adjust your carb mixture or run a cooler range spark plug.

Mr.Utah

Wow, it was still running. Another tribute to toyota.

NJRunner86

It does look like the fuel mixture is off. Since it's a 94, you can't really adjust the carb. I would change out your O2 sensor. If the O2 sensor is faulty, it will trick your ECU into adjusting the fuel. You should change it every 40,000 miles anyways whether or not you get a check engine light.

By the looks of the air filter and spark plugs, the routine maintenance hasn't been done on this thing in a long time.

mightymouse

iTrader: (6)

In regards to the spark plug. Running hot (white residue), What does the gooey stuff between the electrode look/smell like? Looks kinda wet to me and a green tint. Well we both know what looks green in a motor right? Then ask why the heck is my 4runner running hot via the spark plug? Not out right sating the head gasket is gone but if i pulled that plug out of a motor i would be concerned with it and making sure all is well inside that cylinder. Then again it's just a picture on the web and i'm just speculating for you. If it was completely clean and smelled of antifreeze we'd know for sure so keep an eye on it for sure.

MudHippy

Running hot/lean = NO

Ash Deposits = YES

Don't switch to cooler plugs, that will make the problem worse.

You were running rich due to the fact that the engine was starved for air with the clogged air filter element. Simple as that, DUH!

sb5walker

I agree that the plug doesn't show abnormal lean running. There are ash deposits, which are from additives either in the engine oil, or, possibly, from a leak in the power steering pump allowing ATF to get into the vacuum tube that leads to the throttle body (if your pump has vac tubes - mine doesn't but it's an 89).

Plugs from lean cylinders are really super clean, and the terminals are way worn and rounded, more than what's shown in your pic. The computers in most fuel injected vehicles tend to run the mixture slightly lean, so relatively clean and slightly worn plugs are common if the plugs have more than 30k miles on them. Higher mile engines will show some ash deposits on the plugs, from the calcium and magnesium additives in engine oil sneaking past the rings or valve seals - also normal. You might try Valvoline MaxLife 10W-40 to see if tightening up the valve seals helps matters. Also pull the P/S pump vac tubes if you have them to see if they're oily inside (they should be clean and dry).

This plug is from a lean cylinder - pure white, clean terminals with no deposits (but this plug has few miles on it so terminals not worn yet):




A plug from a lean cylinder that has 20k or more miles on it will have excessively worn, rounded terminals like this:


(But that plug is not from a lean cylinder - if it were it would be clean and white. The above plug just had way too many miles on it.)

Some pages on reading spark plugs:

http://www.densoiridium.com/howtoreadusedplugs.php
http://www.tuner-junction.com/TJForu...ark-plugs.html
http://www.autohausaz.com/html/spark...lug-wires.html
http://www.northursalia.com/techdocs/spark/spark.html
http://aboutkarting.com/plugs/
http://roadstarclinic.com/content/view/70/127/
http://www.theultralightplace.com/sparkplugs.htm


EDIT: For the plug threads, try some Permatex Copper Anti-Seize (use sparingly and be very careful not to get on porcelain insulator - that will cause a short for sure).
http://www.permatex.com/documents/td...tive/09128.pdf
http://www.amazon.com/Permatex-09128.../dp/B000HBM8HU

Cuba

Thanks for the replies. I do tend to agree on the ash deposit diagnosis. I have had a few lean running engines in the past, but never this "depositing". I guess I'll run the truck and see how it looks in a week. If there is a correlation between the air filter condition and the plug condition, hopefully I will see a change for the better. I put a swipe of silver grade anti-seize on the threads of the new plugs, so that should make it a bit easier. The plugs are a ball ache to get to as it is without them being tight like that. Nothing a selection of socket extensions and a universal can't handle. Pulling the intake helps.

Moonfish

I'd stick a new one in there and check it next oil change or so. If it was half way out, it would not work properly, it could not exchange the right amount of heat with the head and the spark is physically not where it is supposed to be.

Cuba

Maybe the description wasn't the best. It wasn't half way out. It was just tight to turn out for half the way out.