My car hesitates on the highway 55 m/h and up after about 20 minutes of highway driving, I unplugged the EGR valve to see if it still hesitates, but the problem went away after disconnected the Egr, so is it for sure that the valve is bad? Just wanted to make sure there's no other component that could be also be bad. I have a toyota avalon 1997.
This does not sound like an EGR valve problem. As stated previously, failed EGR valve symptoms tend to occur at an idle. Your problem may be in the passages that feed the inert EGR gasses to the engine. On many engines, there are multiple passages feeding the engine. One for each cylinder. Since EGR flow consists of burned fuel and oxygen, it is an inert gas. Not capable of supporting combustion because there is no oxygen or fuel left in it. It simply takes up space and is used to cool your exhaust output for emissions reduction. If several of these passages plug up, then the remaining cylinders are fed too much of this inert gas and it affects combustion in those cylinders. Normally during highway cruising this inert gas can be fed to all cylinders equally without a noticeable effect on performance. This scenario is possible on any engine that uses EGR ports in the heads or intake manifold to feed individual cylinders. Removing the EGR flow removes the imbalance and your symptom goes away. Barring that, it is still unlikely that the valve is the cause of your symptom. EGR flow at the wrong time such as during acceleration but not at idle can be caused by the vac controls. Hope this helps!
You might be able to get the valve cleaned by spraying cleaner in it or by emersing it in solvent. Check the repair manual and consult with an experienced mechanic. I don't even have a ball park figure of what a new one would cost.
EGR valve will cause trouble at idle, like at a stoplight, not highway speeds.
First of all, the gas pedal on a fuel injected car is a misnomer. It IS an accelerator pedal, but what it really does is only to add AIR to the fuel that has already been injected. If you have to add more air to keep the engine running, then you have a fuel mixture problem, probably from the mixture control unit or a vacuum leak in the attaching air snorkel. You can easily remove and clean the EGR (Exhaust gas recirculation) valve with appropriate wrenches. It's sole purpose is to mix hotter exhaust gas from the exhaust manifold with the incoming air charge to improve the burning of fuel for emission control purposes. It is vacuum activated by higher engine speeds and may jam open from an over abundance of carbon present in the exhaust. You may want to check the operation of your PCV valve and it's hoses for the presence of a vacuum leak, which wuold dramatically affect the power and MPG's. Check your trouble codes at an Auto Zone or similar to see if any of your sensors are on the fritz. Also, specifically, check that your engine is reaching normal operating temperature and that the temp sensor is really immersed in the coolant. If your coolant is low, it doesn't signal the computer to lean out the fuel/air ratio. A good way to check for vacuum leaks is to go to a do-it yourself car wash and shampoo the entire engine bay with the motor running. Any bad plug wires or leaks in the vacuum system should show up now. If I were you I would change the plugs and put in some Bosch Platinum plugs and cork up the vacuum line that runs to your EGR valve completely. It only creates extra unwanted carbon build-up in your intake manifold, anyways. A thorough Gum-out rinse is called for.
