3rd & 4th Generation (1992–1996 & 1997–2001)Toyota Camry Discussion for years: 1992-1996 & 1997-2001
Topics of discussion range from fuel economy, safety, modifications, performance all involving America's favorite family car, the Toyota Camry.
I recently put my 94 Camry V6 through an emissions test with it failing because the HC levels were to high (greatly over the limit) and the CO level were slightly above the normal limit (but a lot less than the HC levels). Also, the NO levels were fine and below the limit. But the second time I did the e-test/smog test, it still failed because the HC levels were greatly high, but this time lower than the HC levels on the first test. The CO level also slightly decreased, but were still higher by 5 to 8 numbers over the limit. Since I purchased this car, I have no idea how it was maintained previously so now I'm trying to do everything I can so it runs better and so that it can pass the smog/emissions test. Before the test I only changed the oil, oil filter, used only high octane fuel, and changed the PCV valve. So far now after the tests, I've only been using and only always intend to use high octane fuels such as 91 and/or 94 octane from the best gas stations, poured in fuel injector cleaner, changed the spark plugs, changed air filter, cleaned throttle body outside and inside (found lots of carbon soot inside throttle body and air intake hose-cleaned it all), and drove the car hard and rev the engine for a while to burn off some of that carbon and clean the engine. Also, recently when I put my finger inside the rear exhaust pipe and looked at it, I still have some carbon soot/powder left on my finger from the inside of the exhaust pipe, and am concerned if it is still burning properly. The car has great power, but I'm just not sure if it will pass the test again. Any advice on what I can still do to help the engine pass the emissions test and make it run more better, or what the problem is that can be fixed that is causing it to fail the emissions test? Thanks.
Do you have a check engine light on? When you did the test, the inspector checks for trouble codes. Did you have any, and if so, what were they?
Your high HC levels are caused by too high of combusion temperatures within the engine. Your EGR system is supposed to allow exhaust gas into the intake manifold to be drawn back into the combusion chamber. Becasue exhaust gas doesn't contain any oxygen, it lowers the combustion temperature, thus reducing the formation of HC. Your catalytic converter is used to remove the low level of HC that could still be made during combustion from a properly working engine, but it cannot handle a significant volume of HC from a non-properly working engine. If a catalytic coverter was exposed to high levels of HC for too long, it could have become rendered ineffective also, and it cannot recover if overly exposed to high levels of HC.
There are ways to inspect your EGR system. I don't know how mechanically inclined you are. If very, we could go through the steps, and the tools you will need. If you are not, or lack the tools, it would be best to take it to a mechanic and have them go through your EGR system.
Just a warning - if you have a problem with your EGR system and if it existed for a long time, repairing it now may not totally solve your problem if your catalytic converter was damaged over this prolonged exposure period.
The Following User Says Thank You to 93celicaconv For This Useful Post:
There is no trouble codes stored and the check engine light is not on. If the EGR system is not circulating enough, could this be caused by a bad EGR valve? I am good at repairs and replacing things, just that I don't really know where the EGR/EGR valve system is, and it would be great if you can show my where the location of it is? Should I replacing the EGR valve? I read that a problem with the EGR would cause high NO, or if it's stuck open it can cause high HC by misfireing, but I have normal NO, I don't feel any misfire, and the RPM is steady at idle.
My bad, Toyota343. I should have looked at my shop manual before I responded. You are right, an EGR system that does not provide exhaust gas back into the combustion chamber results in high NOx emissions, not HC. Got the wrong one.
High HC levels (now that I got my head on straight) would be caused by an overly rich running engine. So your engine may not misfire or idle rough, but it may be getting a little to much fuel.
There are lots of things that could cause this (but not likely the EGR system, and because your NOx levels are OK, your EGR system is probably OK too).
In your 94 Camry V6 OBD-II compliant? If so, you could put a scanner on it (do you have one?). If you don't have a scanner, have an auto parts store that does free code reads tell you if their scanner has live data reading capability. It would be good to see what the LTFT (long term fuel trim) and STFT (short term fuel trim) values are (they are in %, and zero is ideal, and the actual values can be on either side of zero, yours will probably be positive, meaning running richer than ideal). If the engine is fully warmed up, reading the ECT (engine coolant temperature) would be valuable, so see if this sensor is telling the ECM a reasonably acccurate coolant temperature (sometimes these start to fail, and if the sensor is saying the coolant temperature is cold, your engine will respond by running rich).
An O2 sensor could also cause a rich running engine if it is starting to go out.
A dirty injector could cause too little fuel injected into one cylinder, causing one cylinder to run lean, and your ECM compensates to run a longer pulse on all injectors, causing a rich running condition.
How many miles do you have on her, and have you ever changed an O2 sensor, an ECT (engine coolant temperature) sensor, or had any fuel injector service done?
around 210,000 km. currently I'm using fuel injector cleaner with every/every other tank of gas. Since I purchased this car not too long ago, I don't know if the O2 sensor was ever replaced, or coolant sensor (my coolant temperature is average at the middle between hot and cold so I guess that's fine) or the cat converter. Maybe the fuel injectors need to be cleaned for a while before the test? Are there any other cost friendly things I can still do just to make sure the car burns cleaner so it's really ready again for a retest?
Your 94 Camry V6 actually has 3 coolant temperature sensors. The one driving your gauge in your instrument cluster (the sending unit) is fine. You have another at the bottom of your radiator (a switch) that operates your radiator fans (assuming you have electric fans). The one I'm talking about is the ECT (engine coolant temperature) sensor that feeds data only to your ECM. They are all independent. So any one can fail independently of the other. So your ECT sensor could still be bad.
Do you have an engine scanner? Or can you have an auto parts store put a scanner on your car? What would really be important relative to the high HC levels are knowing what the LTFT & STFT values are, and what the ECM is getting from the ECT sensor as far as coolant temperature when the engine is up at normal operating temperature. I think AutoZone, with their Loan A Tool program, will allow you the use of their scanner to. No cost for this test, but you will get back important information.
Theres this trick i done before and it worked. I did it on a 93 corolla. Buy 2 bottles of rubbing alcohol. fill your gas tank up and then put the 2 bottles of alcohol in the gas tank. drive the car for like four blocks and then take it to the smog check. i tried with one bottle first and it just missed the requirements. then the next day i did the 2 bottles and it passed. I tell you by experience so try it if you want to.
Okay, so I changed the cat with a new one after the old one was falling apart inside, and I redid the e-test and it didn't pass again. I also forgot to mention that it does pass on all categories during the curb idle test, but starts failing on the HC when they increase the RPM to a certain amount. There are no fault codes and the readings in the computer/ecm are okay. Could the oxygen and mass air flow sensors have anything to do with this problem? If so, do I need to replace all of the Oxygen sensors (I heard that there is more than one), and can I get a description of where they are located? Thanks.
Toyota343, please read posts #4 & #6 closely. Please provide those readings you are getting from the ECM that are telling you everything is OK. I, for one, would really like to see a freeze-frame of your live data on a warmed up engine at idle and again at an engine speed that is beyond the point where the HC readings fail the e-test. I am sure that analyzing all the data your ECM provides between these two operating parameters will help a lot in determining what your real problem is.
Others on this thread may want to chime in, but I think if your 94 Camry is federal, it will only have one O2 sensor located somewhere in the exhaust system prior to the cat. California emissions vehicles should have two O2 sensors, one located before the cat, one located afterwards. A bad O2 sensor can cause the problems you are seeing. So can a MAF sensor. So can an ECT sensor. Some of these parts are expensive. Maybe its just me, but I wouldn't just throw money at it, because I believe your ECM will provide data that can at least narrow the problem down, if not pinpoint it.
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