Very new to this, anywho!
1. Check engine light refuses to go off now. I am pretty sure it due to now screwing gas cap but even after screwed tighly won't go off.

2.Screaching noise when I start, I think its time to change my timing belt. Any toyota mechanics out there? Spring, TX

 

Best bet is to read out any trouble codes stored using an ODBII scan tool.

Some autoparts stores will do this for free.

Gas cap can be just one of many issues.

V6 or 4 cylinder?

4 cylinder now has timing chain.

Have you checked the belts driving the components such as alt, AC and PS? More likely this type of belt then the timing belt.

Timing belt has teeth needed to keep the cam and crank location in time. A slipping timing belt would result in the engine not running or running very poorly.

 

V6 SLE, I will go to Autozone to get the check engine checked! I should probably say I am not car savvy so most of what you mentioned is pretty foreign to me.

Which is why I signed up with this forum to learn more.

 

If you look at the passenger side of the engine you will see a belt, if the noise is a belt, this belt may be the one making the noise. It powers the engine accessories such as alternator, power steering pump, etc.

The timing belt has teeth, see photo in link below:

http://www.google.com/imgres?imgurl=...ed=0CBoQ9QEwAA

These teeth engage sprockets to turn various components of the engine. The photo below has a diagram for a 4 cylinder engine.

http://www.google.com/imgres?imgurl=...ed=0CBwQ9QEwAQ

If the timing belt were screeching, it might mean the belt were slipping. If the belt slips, the pulleys in the diagram would no longer oriented to turn all together at the right time, the result would effect engine operation.

This belt has teeth, the odds of it slipping like the first belt mentioned are very slight. This belt is hidden under a plastic cover in front of the engine, behind the first belt mentioned.

As to the gas cap. It is possible for a loose cap to cause the light to come on and tightening the cap to fix this problem.

However, the light can also come on for a host of other reasons. When the light is on, it means a trouble code(s) number has been stored in the cars computer. Each code has reference data for it. Meaning if it is XXXX code, the reference data provides specific info as to what is wrong and where to start troubleshooting.

Thus why guess at the problem when these codes can be outputted.