I have a 1999 camry CE (4-cyl) with about 250K kilometers on it. Lately, it's been having a strange problem. When I first turn it on and start to drive it, it runs perfectly. But, after it's been driven for 10 or 15 minutes, it starts to shake a bit. It's less noticeable at highway speeds, but it's incredibly noticeable when I hit the brakes. It's as if I was pressing them, then letting them go, then pressing them, then letting them go, but really fast, making the car jerk. As the car slows down, the frequency of the jerkiness also slows down. Kind of like what anti-lock brakes would do if you really slammed them on, though this car doesn't have anti-lock brakes.
Then, when I'm idling, there's something like a scraping noise coming from somewhere in the back end of the car. However, it doesn't always happen. It used to happen maybe once every 2 or 3 months, but lately it's been more frequent. There are times when I can drive the car and it won't happen at all, but there are other times when it's constant whenever I'm idling. It's pretty loud, and therefore very annoying. My car idles around 500 RPM... if I bring the RPM up to around 800, the noise goes away. However, this means that when I'm at a stop light, I need to keep one foot on the brake and the other one slightly pressing the accelerator. That'll probably kill my gas mileage, not to mention the fact that it's probably not exactly the safest thing to do.
I haven't brought the car in to a dealer yet, because they always want to charge me thousands of dollars to "fix" things that aren't really broken, and I simply can't afford that.
Does anyone have any thoughts on what the problem could be?
I never go to dealers unless it warranty work, they charge 2-3x more than my mechanic. 500 rpm is to low 6-700 is better. When car is cold the gas mixture is richer, when it warms up is when you have an issue. It sounds like a simple tune up is needed, the scraping in rear is probably something loose. Fine a good local mechanic. If my car ran at 500 rpm it would not idle well.