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toyomoho -> RE: CAMRY 00 missfires and vibrates (6/7/2008 9:05:00 AM)
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One thing to keep in mind is not all the cars systems are monitored by the computer. Thus it is very possible a part has a problem but because it is not monitored there will never be a code set. The computer monitors the cars systems over time. Some problems are required to occur 2 times before a code is set and then must occur within a certain set of parameters such MPH, RPM, coolant temp. The computer looks for variations in sensor voltage, current, etc. output but only when these parameters are met. Otherwise codes would be tripping when the engine was cold started, at full throttle, etc. Conditions that are not typically for 98% of the time the car is being driven. The ODBII system was mandated by the EPA to monitor emissions systems, alert the owner to possible problems and rapidly diagnose them. The system does have codes to warn of some types of engine misfire. If the engine dies when driving, vacuum to the brake booster does also. The result is no boost and much harder breaking. The brakes themselves are still working normally, the issue is you now need to really press on the pedal because there is no longer boost helping your foot. The car is still safe to drive If you keep in mind the extra foot pressure needed to stop. If the temp gauge reads OK unless defective the engine is not overheating. If the engine dies after releasing the throttle would look at the air valve (IAC) and fuel system. If the engine hunts at idle would look at the throttle possition switch, A/C idle up system, IAC valve, MAP sensor, fuel system. The common issues are IAC valve and fuel system, not all of the full system is monitored, the IAC is not monitored. Thus no code can be set for some problems. IAC valve issues are common. The symptoms can be high or low idle after engine start up, hard starting, idle hunting, engine dieing. But once the engine dies, it typically starts up just fine and runs OK until the issue reoccurs. Do a Google search on "cleaning IAC valve." You should find numerious hits, some may have photos. You can try this yourself with only a few tools. If interested in trying this post back for more info.
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