Loud noise from inside car on 1993 Toyota Corolla

I own a 1993 toyota corolla LE with approximately 217,000 miles on it. I have recently just changed the oil and filter and replaced the exhaust manifold on the car. A mechanic and family friend of ours replaced the manifold. The loud vibration noise coming from outside and inside the car was suppose to go away after replacing the manifold. Once starting up the car from the outside the noise cannot be heard that much. However when sitting in the driver side I hear a loud noise at times. Mostly when I'm on the highway and when first started up. When the car is started it seems to idle high, which is normal to idle high when it is cold. Once the engine warms up it seems to idle ok but sometimes still idles over the 1000 rpms. Now I don't know if the noise is just something that is with this older car seeing how it has high miles or if something else is wrong. Please help.

by in Greene, NY on October 13, 2010
1 answer
ANSWER by on October 13, 2010
It could be many things, unfortunately and without experiencing the problem first hand or being able to do some basic diagnostic tests its hard to say. I have replaced quite a few exhaust manifolds that were cracked. Perhaps after disturbing the manifold to replace it the flex pipe of the exhaust now leaks, or a gasket is not sealing right in the exhaust system. Check that the air filter housing is secure that it is not air induction noise you hear. The idle speed raising confuses me unless the previous exhaust manifold was leaking and allowing "false air " in, and the O2 sensor was picking this up and altering the idle speed. Other possibilities are worn engine mounts or the exhaust system itself causing some sort of vibration, but ask your friend to have another look at it it may be something really simple.
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