long time lurker, first time poster (well, its been awhile since i've posted)
anywho, my 93 4 runner failed the smog test today and was wondering if anyone can give me some helpful tips or advice on what could be the problem or possibly a rough price figure on how much it would cost to replace whatever necessary part/parts to have my baby pass smog.

The part of the ASM Emission Test that failed at 25mph:

HC (PPM)
Max: 53
Ave: 64
Meas: 64

any advice would be great!
Thanks in advance!!!

 

The HC was not far off. There is a chance it would pass the next time. What was the weather like when the test was done? If it was later in the day maybe in the AM where the air might be cooler/more water vapor. I know it sounds funny but it does make a difference some times. Your so close I might just clean up the plugs and air filter and try it again. Other wise all things considered equal replacing the cat converter would be a sure bet to pass. There are some cheaper aftermarket ones and ones on Ebay you could have welded on at a reasonable cost.

 

I just tested mine today ('85/22REC) and HC was between 4 and 9, new cat and O2 sensor. You could also try and dump a gallon of denatured alcohol (a.k.a. shellac thinner) in the gas tank. The alcohol has extra oxygen and more oxygen and that helps burn more of the fuel (i.e. Hydro-Carbon).

 

Thanks for the help! The test was performed late in the afternoon so that could be a factor. I also shouldve mentioned that the only mods i've done was KNN air filter and Magnaflow exhaust with 2.5 inch diameter pipe from the cat back. And, with the gas prices increasing in California, i've been filling up with the lowest octane.
Someone did mention to perform a tune-up, cleaning up the air filter, and filling up with super unleaded to help it pass. I'm gonna do that after work and hopefully it'll help. Thanks again guys!!

 

Be careful running too much alcohol in the tank that can have other bad effects on the system as well.
You are close to the limits so that is good news (ie not likely anything major).

First of all, was the truck fully hot (ie driven for at least 30 min) when the test was done?

Other things to do are typical tune up stuff (cap, rotor, plugs, fuel filter).
You may need to replace the O2 sensor if it still doesn't pass and finally look at replacing the cat converter.

 

Yes, the test was performed right after work which is about a 30 - 40 minute drive. Also, the smog test station had the truck running at idle for approximately 15 minutes before performing the test.

How much does a O2 sensor cost? i know the cat is probably gonna cost me more than $75 i think.