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Car Forum / Toyota / Toyota Trucks / March 200896 5VZ 4Runner fails SMOG test
A friend of mine has a 94 5VZ 4Runner. It failed on the 15mph test, too much NO more than double allowed. It passed fine on the 25mph test, but still in the upper limits. CO2 and HC levels are within normal or below average. The SMOG tech suggested it was running too lean. I don't think it's the CAT, IMHO, but I'm leaning towards clogged injectors or bad MAF sensor, but usually it would run rich if the MAF is bad. The EGR valve was recently replaced, but I'm not sure if it was replaced before or after the SMOG test. What else would cause the NO to be so high? TIA JW P.S. I'm referring to California SMOG test. >A friend of mine has a 94 5VZ 4Runner. It failed on the 15mph test, too much >NO more than double allowed. It passed fine on the 25mph test, but still in [quoted text clipped - 12 lines] > > P.S. I'm referring to California SMOG test. High NO would be casued by an inoperative EGR system. > >A friend of mine has a 94 5VZ 4Runner. It failed on the 15mph test, too much > >NO more than double allowed. It passed fine on the 25mph test, but still in [quoted text clipped - 16 lines] > > - Show quoted text - High NO implies higher than normal combustion temperatures. A lean mixture can cause that. A faulty thermostat or a malfunctioning cooling system can raise temperatures too. Is the temperature gauge reading high? A faulty EGR system, which cools engine temperatures by inserting recycled exhaust gas into the cylinder, can also cause combustion temperatures to get high. In exteme cases, noticeable pinging can be heard. Good luck. Al >>A friend of mine has a 94 5VZ 4Runner. It failed on the 15mph test, too >>much NO more than double allowed. It passed fine on the 25mph test, but [quoted text clipped - 16 lines] > > High NO would be casued by an inoperative EGR system. Thanks for the Replies! The EGR was replaced before the test and engine temp is normal. Unless the new EGR is bad or the vacuum lines are leaking clogged, I don't know what else to think of. Also the engine runs normal, no unusual pinging or miss fires at idle. We're gonna try to clean the intake and throttle body, it did seem a bit dirty, and replace the air filter. Like others said, check your EGR system. Also too advanced engine timing or lean mixture can do it too. Check things that raise combustion temperature. Check following: http://www.asashop.org/autoinc/oct2004/techtips.htm > A friend of mine has a 94 5VZ 4Runner. It failed on the 15mph test, too much > NO more than double allowed. It passed fine on the 25mph test, but still in [quoted text clipped - 12 lines] > > P.S. I'm referring to California SMOG test. On Mar 12, 11:50 pm, johngd...@hotmail.com wrote: > Like others said, check your EGR system. Also too advanced engine > timing or lean mixture can do it too. Check things that raise [quoted text clipped - 20 lines] > > - Show quoted text - When the EGR system fails it is often not the EGR valve. The EGR system must be checked. That includes the vacuum lines but most importantly the passageways that carry the exhaust gas. Given the corrosive nature of exhaust gas, problems with components that it routinely contacts are not unusual. Good luck. Al > On Mar 12, 11:50 pm, johngd...@hotmail.com wrote: > [quoted text clipped - 28 lines] > corrosive nature of exhaust gas, problems with components that it > routinely contacts are not unusual. Good luck. Al To start with, wasn't the 94 4runner a 3VZ 3.0 liter not a 5VZ? If so, I have seen the EGR modulator (Toyota pt # 25870-65010) get a pinhole leak in the diaphram. The modulator is located right above the power steering pump and is mounted in a clip on the intake plenum. You should be able to rev the engine and see if the stem to the valve on the EGR valve is moving when you increase the engine RPMs, if it is not, you either have a stuck EGR valve or a vacuum leak leading to it. It's a 96, I'm familiar with what your describing, I have a 93 with a 3VZ. My friend is supposed to get it retested this week. > To start with, wasn't the 94 4runner a 3VZ 3.0 liter not a 5VZ? If > so, I have seen the EGR modulator (Toyota pt # 25870-65010) get a [quoted text clipped - 4 lines] > RPMs, if it is not, you either have a stuck EGR valve or a vacuum leak > leading to it. |
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