Specialbrownie

I'm new and just bought a 2000 Civic Ex that almost turned out to be a lemon. I have a few issues with it and would like some DIY help.

1. I have three sensors on. My speed sensor, knock sensor and idle system sensor. My speedometer and odometer both do not work so I'm thinking that's why the speed sensor is on and would like to know how to fix that issue. I don't why my knock sensor is on as my engine doesn't knock. Now, my car idles fine when not using anything that requires power while idling. It's when the A/C, power steering or brakes are used in idle when something weird happens. Instead of the idle increasing to compensate, it decreases about 500 rpm, it doesn't stall but it causes the car to shake. I need to know what to do to solve these problems as I'm probably losing gas mileage with them on.

2. My VTEC system seems to have failed. It's a 1.6 5 speed SOHC VTEC. Is the cause just a simple failure of the VTEC soleniod? The engine runs fine, the cams are obviously working, it's just when I hit the stock VTEC engagement of 5500 rpm, I don't feel a boost, a kick, nothing. So I'd assume that my VTEC is bad and the only thing I could think of would be a bad solenoid. Also, does anyone know a link to a website that sells a VTEC tuner? I'd like to set mine to around 3800 rpm.

3. My last inquiry is about where the speed limiter is. While doing the obvious and allowing me to travel passed speeds of 120mph, I've also heard it increases horsepower and gas mileage by removing the speed limiter. So, I'd just like to know where it is and a safe way to do a DIY removal.

If any of these questions can be answered, I'd be greatful. I don't trust the mechanics in town and bet that none of them understand how to properly work on a VTEC. Thanks!