Failed Emission Test - WHY?

There are no engine lights on. I have not performed a tune-up as I just bought the car and brought it in to be e-tested. Air filter is clean and the car has a tankfull of new regular gas.

You failed to mention if you've tuned it up recently. Running smoothly is not an indication that it's perfectly tuned. Changing the wires, distributor cap and rotor, spark plugs with NGK or Denso, and air filter might do the trick. I would also suggest replacing the old fuel by either using it up, draining it, or a combination of both.

I would suggest to stay away from the "home brews" that others are using. If your O2 sensors are bad, a check engine light will typically light up.

It looks like the car passed everything except the Hydrocarbons (HC) test above idle.

From this article about emissions testing:

"Hydrocarbon failures mean unburned gasoline is passing through the engine and entering the exhaust. The three most common causes include ignition misfire, lean misfire and low compression (typically a burned exhaust valve). Ignition misfire can be caused by worn or fouled spark plugs, bad plug wires or a weak coil. Lean misfire results where there is too much air and not enough fuel, so check for vacuum leaks, dirty injectors or a fuel delivery problem. In addition to these, hydrocarbon failures can also be caused by oil burning due to worn valve guides, valve guide seals and/or rings."

As viperkiller mentioned, do not try any home brews like Coleman gas, etc. Premium fuel will not help.

What may help is a bottle of fuel injector cleaner like Chevron Techron or the stuff that Toyota dealers sell, although I doubt if it would make much of a difference.

If you replace ignition parts, I recomend using OEM ignition parts to increase your chances of success.

You an try cleaning the Mass Air Flow Meter located at the outlet of the air filter housing with carb cleaner.

Regarding O2 sensors, the #1 sensors on the exhaust manifold control fuel mixture, the #2 sensor by the catalytic convert monitor the converter. Check both #1 sensors operation before replacing them so that they are not replaced needlessly.

I think what the car failed is the 25 percent load test. I would check the EGR valve for normal operation and then clean the seat valve. If EGR operation is normal then it may be just a engine temperature sensor. Like Viperkiller says, I would not introduce any type of "home brew", camping stove fuel, or anything of the sort. The Hydrocarbon ppm reading indicates a high level of unburned or possibly raw fuel. If you just purchased the car, make sure that first, the "check engine light" does work correctly (they normally illuminate with the key in the "on" position but check the manual for certain). If it doesn't work then start with that, then any codes that may be set. You did not mention the vehicle's mileage.

Yeah, I'd stay away from Stove fuel, too, unless the car is a beater and you don't really care about it long term.

Do the tune up with Real Toyota parts. Don't go to Canadian Tire! ;) Like VK said, Denso or NGK plugs, and real Toyota cap and rotor if equipped. The only aftermarket items I use in the tune-up is NGK plug wires, since they are OEM anyway.

Well guess what? The engine light came on after driving it about 75 km. I noticed the engine oil and transmission oil are both pretty dirty. Would dirty oil be enough to trigger an engine light and even be the reason why it fail the emission test?

I've since added some "Guaranteed to pass" additive to the gas (after the light came on) and will do an oil change... I've also bought a new rotor but not the cap itself as it comes with the wires and wanted $120 for it. Here hoping the oxygen sensors don't need to be changed as they also want $220 for OEM or $116 for universal one. I may end up changing the spark plugs but I will check them first.

IMHO, you're going about it the wrong way. What you need to do is to learn what the real problem is. You have a check engine light on. Get a proper diagnosis to find what is causing the check engine light to come on.

You also need to learn what is required to pass. It may be that you can pass, even if you fail the test. In some states, I beleive, once you have spent a certain amount of money to fix the problem, you automatically pass, even if your emmissions are too high.

So find out what is causing the problem. Adding the guarenteed to pass crap won't do that. Then fix it.

In other words, arm yourself with knowledge.

Jeff

Well guess what? The engine light came on after driving it about 75 km. I noticed the engine oil and transmission oil are both pretty dirty. Would dirty oil be enough to trigger an engine light and even be the reason why it fail the emission test?

****** No, dirty motor and transmission oil will not be enough to trigger a check engine light or cause an emissions test failure unless the oil is basically the consistency of tar. *****

I've since added some "Guaranteed to pass" additive to the gas (after the light came on) and will do an oil change... I've also bought a new rotor but not the cap itself as it comes with the wires and wanted $120 for it. Here hoping the oxygen sensors don't need to be changed as they also want $220 for OEM or $116 for universal one. I may end up changing the spark plugs but I will check them first.

******** As Jeff advised, changing parts is not the proper way to go about trying to fix the problem. I forget what kind of vehicle you have, but you should check trouble codes first to see why the check engine ight is on and then post the results of the most recent emissions test, along with the applicable limits in your area.

You should be able to find specs online, by my guess would be the correct gap to be ~.030, and out of spec at ~.080.

'94, eh? This is Pre -OBD II. Google Toyota Trouble Codes and you should be able to find a method for getting the code out of the ECU. Ray O has a link to a Camry diagnostic site, maybe if you ask nice he'll post it.

I know where the connector is on my three cars, but on yours...

You should have a connector under the hood that says, "Diagnostics". I can't remember which contacts, but the easiest thing to do is shove a paper clip in there to jumper them and then count the flashes on the Check Engine light. This will give you a clue.

This is for a Supra, but most Toyotas are similar:

Short pins E1 and T, turn the key to the ON position (Don't start the car!) and count the flashes.

These are for a 4WD, but they are about the same:

Here's a better diagram:

And another:

Good luck!