What is causing my Honda civic RPM to act crazy?

I need help determining what is causing and idle problem with my 99 honda civic ex coupe. So just recently about 2-3 weeks ago i took my car to get my thermostat and coolant sensor replaced. After I was giving it back, i noticed that the next day it was reving high at about 1,300-1900 then it would drop to normal (1000) after few mins. Then sometimes it drops close to 400rpm. This happens every time i'm at a stop. I was thinking about taking it back to the mechanic but i'm not because first, he charged me a lot, and second i don't have a good feeling about this guy anymore. Also, i got a check engine light come on like 2 weeks ago, but then it went away. Now it came back up, I'll try getting the codes tomorrow but as of now any ideas?

AC making loud vibration and revolving noise on 2002 honda civic lx?

The noise doesn't always happen when the ac is on but it does for most of the time. It happens more loudly than normal and more often than normal whem I've been driving the car a lot that day. What could be making this noise? The compressor? I just replaced front and rear sway bar links, outer passenger tie rod, and exhaust manifold.

Car temperature guage problem?

I took a trip to Pittsburgh this past weekend. It was fine for the six hour drive, the next day I drove it, it overheated. So I had it towed to Honda. It's a 2004 Civic LX. They replaced the radiator, the thermostat, and the cooling fans. Drove it back to New Jersey today, and I noticed the gauge went all the way to hot only when I hit traffic and I had slowed down. It went back to cool when the car was crusiing, and kept doing that the last hour or so of the trip, depending on stopping and going. What could possibly be the problem if all of those areas got fixed?

Car is dying? Need new form of transportation? Think bank will give me a loan?

The trans on my car is going out and needs more $ in repair than its worth. We don't have bus service out here and no o e can drive me to work. Work is 30 mins away by car. Do you think the bank would at least lend me 3 grand to get a reliable scooter? I don't have any credit, I've never taken out loans or used a credit card and the dealership won't let me make payments because I don't have credit or a cosigner. I'm so tired of cheap used cars capping out in me (this is the 3rd I 3 years, one honda civic, one camry, and now this sentra) at this point I rather get a small new honda scooter and just deal with the rain instead of not being sure if my car is even going to run when I get in it. I never need to go more than about 35 mph anyway. Do you think my bank would give me a loan?

My 94 Honda Civic LX Speedometer Fluctuates?

Speedometer Problems! Okay so, I just bought a used 94 Honda Civic LX. It has 160,000 miles on it. I bought it from a town two hours away from my home. When i tested it, it was working, then after i bought it from the person, i went on the highway following my friend and it was working for about 30 minutes until it started fluctuating like crazy. And it still fluctuates after driving for a couple of minutes after starting the car. I just bought the car and i'm pretty disappointed about the speedometer because my old car's speedometer wouldn't work anymore. Anyone knows what the problem could be? Or maybe what's causing it?

Where can I get an exhaust system like this?

Here's a video of a compilation of Honda Civics with ricer exhausts (mainly), but the only one I really want you to see is the first one. The clip is from 0:00-0:09. So it's only 9 seconds:

So I have a 2003 Mitsubishi Eclipse GS. I know they're 2 totally different cars, but I wanted to see where I could get a ricer exhaudt like this one. Raspy, loud, and annoying. I have one that's pretty loud, but I want one about like this.
Where could I get one and about how much would it be?

By the way, if you're going to put something smart about ricer cars, go ahead. I don't care. I don't like around you so you won't be hearing it so just give me an answer that'll actually matter.