Intermittent Engine problem

[Tjhilliard]

I have a 1999 Solara coup with the V6 engine and have had an engine problem for the last three or four years. I have been to several dealers and an independent garage without finding an answer. After the engine has been running a while, it beginns to run roughly with RPM's flucuating whether it is idling or running on the highway. At the same time, the exhaust gets a bad smell, probably unburnt gasoline but I am not sure. It is strongly dependent on the temperature. Durring the Summer it will do it frequently and in the Winter I will have to drive it much greater distances before it happens. No light comes on and it doesn't seem to produce an error code. I started taking it into the dealer only when the problem started and had them check it then. One dealer had it twice and then pronounced it due to a bad Cat Converter. I had that replaced but the problem came back. The last time a mechanic took it for a long test drive but said the problem stopped before he could pin it down. Any thoughts on this?? The O2 sensor has also been replaced. The problem started around 75,000 miles and is now up to 104,000.

[WortownSolara]

Im gonna have to put some long thougth into this one. Try one more thing. Camryman.org, Try running a search of rough idle. and see what you pop for searches.

[marc780]

Maybe it is just a dirty throttle body and/or IAC. That would be the reason theres no codes. So clean em up, its easy, plenty of posts on this subject so i wont type it again (lotta posts on camry forum too on this subject). Its worth a try.

[aggressor]

hmmm. I might be way off, but I just remembered the similar problem with my friends car. He had a 1992 Honda Accord with a dead odometer. He has deffinetly drove the thing way over 90k without changing the timing belt and water pump.... The RPM would fluctuate at idle between 500~2500 every 2 secs. and at speeds under approx 50MPH it would feel like somebody is tapping on a gas pedal. There were no codes either... Once we've changed the belt and the pump, the problem went away. So my first question would be - Have you changed your timing belt and water pump?

[damiankaren]

Not sure if your car has an exhaust gas recirculation (EGR) system. If it does....

I had a similar problem with a 1999 V6 Camry. RPM surging at small throttle openings. It turned out to be a faulty EGR position sensor. An easy way to test this is to temporarily disconnect and plug the vacuum line that operates the EGR. This is OK for a short while. If the problem goes away it points to an EGR system fault.

Hope this helps.