[stcywll]

Hello,

This is my first post . I am not a 4 runner owner but I am trying to help my girlfriend’s dad. They have a 93- 4 runner that runs great, always s past the emission test, until last week when it failed miserably.

The truck is a 4 cylinder and has 285 000 km on it . Since the last emission test it has become a second vehicle now, used mainly for short trips around town in the winter.

I have checked the plugs, wires, air filter ( all good) and ran injector cleaner through it as well. I just replaced the cold start injector (with a used one) because it was having problems starting in cold weather, but it is still hard to start. I know the car probably needs a long drive and the cat converter needs to be cleaned out. Just wondering if there is anything specific or a common problem that makes them fail (other than the cat and 02 sensor being old). The truck is a rust bucket now and we don’t want to spend $$$$ on it anymore.

Thanks

[fourwd1]

What failed and by how much?

[slowpoke99]

Not sure how they do it up there but here they give you a printout showing whatever codes your ECU may throw if it fails. I know guys that failed simply because their fuel cap was bad. Sometimes it's that simple of a fix.

[giro]

The O2 sensor or cat could be likely, especially if they are original. Both are pretty cheap, relatively.

The problem is if something upstream is causing a problem, and then fouling either of those things. For instance, when a friend's car failed smog, I think it was already having head gasket issues, likely letting in coolant or oil into combustion since he went through at least one o2 sensor. That's just a guess on his, but it later blew it's head gasket, so it seems probable.

So it all depends. Rockauto has oxygen sensors for $40 or so for my '92 v6, and when I replaced my cat years ago (when the original was stolen) I bought it for just $80. And a gas cap o-ring or cap is even cheaper. So it all depends.

[airdreams1]

We need more info on what part failed Hydrocarbons or CO2 & the numbers.

Some times all you need is a really long drive just before you go in to test. That way the cat is @ its max temp.

Also fill up with all new high grade gas not old stuff thats been sitting sitting around for several months. If you can get non ethanol gas, go that rout even if more expensive. The rig will run better, last longer & produce less smog. Thats a fact, not an opinion. Its been proven time & time again.



some basic info:

WHAT CAUSES HIGH CARBON MONOXIDE (CO)?

Below are common faults which are likely to produce high Carbon Monoxides (CO) and Rich Fuel Mixtures. Carbon Monoxide is a by-product of incomplete combustion. Carbon Monoxide exceeding maximum limits, can be due to a number of emission failures ranging from inadequate air intake to defective engine computer sensors. This condition is referred to as a "Rich Fuel Conditon".

What causes a rich fuel condition?

1. Dirty Air Filter - The number one overlooked emissions component, yes, "emissions" component is the engine air filter. A dirty air filter will absolutely restrict air flow, thus disturbing the proper 14.7:1 air/fuel ratio required for optimum fuel combustion.

We recommend replacing the air filter at the manufacturer's required intervals; usually every 15,000 miles, or at least before your vehicle's smog check.

2. Faulty Oxygen Sensor (O2 Sensor) The Oxygen Sensor is responsibly for delivering information to the ECU (engine control unit) or ECM (engine control module) relating to the oxygen content in the exhaust stream after it has left the combustion chambers.

The engine control computer will determine how much fuel to inject into the combustion chambers based on this data. The more oxygen in the stream, the more fuel the computer will deliver, and visa-versa. A defective O2 sensor will cause increased carbon monoxide emissions. More about oxygen sensors.

3. Defective Manifold Absolute Pressure (MAP) Sensor - The MAP sensor determines the level of vacuum created during an engine's intake stroke, and sends this information to the ECU. During low vacuum the MAP sensor assumes the engine's throttle is in some degree open, meaning you've stepped on the pedal. It relays this information to the ECU. The ECU, in turn, sends commands to the fuel injectors, or carburetor, to increase fuel delivery.

A defective MAP sensor will not report the correct information to the ECU, thus disturbing air/fuel ratio. Usually when the ECU senses a defective MAP sensor it will learn to ignore its data, and rely on preset values, and other sensors such as the Throttle Position Sensor (TPS), and Engine Coolant Temperature (ECT) Sensor; Fuel delivery will not be as accurate and high CO may result.

4. Defective Throttle Position Sensor (TPS) - Obviously a very important emissions sensor; the TPS relays information regarding the position of the air intake system's throttle plate. The throttle plate, located after the engine air filter and before the intake manifold controls the amount of air entering the combustion chambers. It is usually manipulated by the gas pedal via a cable. On late model vehicles the throttle plate may be controlled electronically. A defective throttle position sensor will confuse the ECU into thinking the vehicle's operator is demanding more or less fuel, when neither is really neccessary. Most often a faulty TPS will cause high CO, as an engine's ECU always prefers to send more fuel rather then less, in an effort to avoid a lean fuel mixture and subsequently higher engine temperatures.

5. Defective Engine Coolant Temperature (ECT) Sensor - Low engine temperature requires more fuel. When the ECU is unable to determine what the engine's accurate temperature is, it will not adjust fuel delivery properly; resulting in high CO. As explained above, the Engine Control Computer prefers to send more fuel rather then less to avoid a lean fuel mixture.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~

WHAT CAUSES HIGH HYDROCARBON (HC)?

Below are common failures which are likely to produce high Hydrocarbon HC. Hydrocarbons are basically raw fuel, otherwise known as Gasoline. High Hydrocarbon (HC) emissions are almost always a sign of poor fuel ignition. However, it's not always that the engine's ignition system is responsible for high Hydrocarbon emissions. Read on.

1. Improper Ignition Timing - Engine ignition timing is measured in degrees before or after Top Dead Center (TDC). Example of an ignition timing failure would be in the case where an engine's ignition timing is required to be set at 10 degrees Before Top Dead Center (BTDC) and instead is set to 15 degrees BTDC. This fault will not only cause a smog check "functional failure", but will increase Hyrdocarbon (HC) emissions as well. California allows 3 degrees +/- off of the manufacturer's required setting. Note: Late model vehicle's may not have a distributor, and therefore no timing adjustment will be needed. On these engines timing is electronically controlled by the ECU (Engine Control Unit).

2. Defective Ignition Components Your vehicle's ignition system consists of the ignition coil/s, distributor*, distributor cap*, distributor rotor*, ignition wires, and spark plugs. If any of these components are defective the engine will produce high hydrocarbons. A common reason ignition components perform poorly is due to carbon build-up. High ignition voltage traveling through the air pockets within these components form carbon. Carbon acts as an insulator between paths of electricity, decreasing the energy required at the spark plug to ignite the air/fuel in the combustion chambers properly. *Distributor-less engines do not have these components.

3. Lean Fuel Mixture - Any condition which will cause unmetered air to enter the intake manifold, and ultimately the combustion chambers, will cause high hydrocarbons (HC). This condition is called a lean miss-fire. Such faults as vacuum leaks and gasket leaks will cause lean fuel/air mixtures. Broken, disconnected or misrouted vacuum hoses will do the same. It is also important to note that many engine components rely on engine vacuum for proper operation. If any of these components are defective, externally or internally, they may cause large vacuum leaks as well. A good example of such a component is your vehicle's power brake booster.

4. Defective Catalytic Converter - A defective catalytic converter (CAT) may be responsible for high HC, CO, and NOx emissions. The Catalytic Converter, commonly referred to as the CAT is a component designed to continue the combustion process within itself and emit a more thoroughly burned and less harmful emissions containing exhaust. The most accurate way to find out if your vehicle's CAT is working efficiently is by using an exhaust gas analyzer. Unfortunately this tool is fairly expensive. Testing the CAT should be conducted at a smog check repair station.

Some obvious symptoms of a bad CAT could be any of the following:

a. Major loss of power over 15-25 mph. This may be an indication that the catalytic converter is plugged up and restricting exhaust flow.

b. Strong sulfer or rotten egg smell emitting from the exhaust on an otherwise good running vehicle. This may be an indication that the Catalytic Converter isn't burning fuel completely, instead storing it, then releasing it as hydrogen sulfide.

c. Loud rattle being heard from inside the CAT. This may indicate a broken Catalytic Converter substrate. You may want to insure this sound is not due to loose exhaust components, i.e. broken muffler flanges, loose exhaust pipes, loose or cracked exhaust manifold.

5. Defective Air Injection Components - Faulty smog pump and related emissions system components will cause high HC. The air injection system is designed to introduce additional oxygen, after the metering system, to the engine exhaust as it exits the exhaust manifold, or directly before it enters the Catalytic Converter; thus burning whatever remaining fuel (HC) in the exhaust completely.

6. Low Cylinder Compression - This fault is one of the less common high HC causing problems we encounter. Reasons an engine may have low or no compression in one or more of its cylinders may include things such as burned intake or exhaust valve/s, defective valve guides and/or seals, defective piston rings, and burned head gasket/s. A wet/dry cylinder compression test will diagnose this fault. More then often if such a problem exists it will be very apparent. You should notice rough idle.

[stcywll]

OK, thanks for the reply's. They do the tailpipe test on anything older than 1998 here, so I got the emission report today.

HC- Limit is 200, reading 429@ 2500 rpm and @ Idle

CO- Limit 1, reading 4.29@ 2500 rpm, 6.44@ Idle

Took a look at the cat. today. Looks like its rusted on pretty good and wont be easy to remove without a torch, otherwise I would take it off and clean it out.

I haven't driven the truck in a while, but she told me its sort of as sputtering in 2nd gear. Now I'm thinking EGR problem Possible vacuum hose problem?

[Manpdhi1]

Hi guys,

I am new here. I am curious what you guys think after seeing my 1993 Toyota Pickup 22re 2.4L Automatic California Emissions test results. Also what does ignition timing: PB04 means?

Is this good running truck? Mileage is 186,500.

Thanks

[RonJR]

This is an old thread, but your question is up-to-date, so I'll reply.

Your NOx emissions look great. That means your EGR system is working properly.
CO and HC are passing, but creeping up. Your O2 sensor may be getting tired. Mine did the same thing last year, and replacing the O2 sensor (the upstream one, before the cat) dropped the HC and CO emissions by 2x or so.

O2 sensors are cheap and pretty easy to replace, unless rusted in badly. Get a Denso from Rock Auto. Don't buy a parts store substitute.

Not sure what PB04 means - I'm not in California. That's not a code from the truck itself - the truck only produces two digit numerical codes. Probably a code that says the tech checked it with a certain methodology. You'd have to ask the tech.

Looks healthy for 186,000 miles.