Valve cover vent hose
 

So I've been trying to troubleshoot why my car sometimes has problems starting even though it turns over fine. I was going to check plugs, coil packs, igniter and possibly fuel filter. When I popped the protective cover off of the engine I noticed that one of the hoses running from valve cover to valve cover was cracked and showed signs of leaking a liquid substance. I have a general idea of what those hoses are for but what sort of problems would something like that cause. I am going to replace it asap.

Thx

It's just a PCV hose...which has nothing to do with starting unless your PCV valve is bad. I agree with your plan to check the plugs, and fuel filter. The coil packs I'd only check if your Supra has more than 100K miles. Also add checking the air filter to your list, and run some fuel injector cleaner too (if you haven't recently).

So I checked all my iridium spark plugs and they were that orange/tan color on ends which is the color they should be according to an article I read. My coil packs metered in at 0.38, 0.38, 0.38, 0.40, 0.36, 0.35 ohms which I think is in tolerance. No oil filled spark plug wells. Replaced the PCV hoses on the valve covers and the air filter.

I also took off my throttle body and cleaned it out with throttle body cleaner. There was a lot of carbon build up as I had anticipated. I had previously cleaned the IAC valve so I didn't bother it. It now seems to idle smoother. Next step is to check the fuel filter.

Something that I had just been ignoring but now I think it should be looked at, is a problem I have been having with my throttle when I'm really stepping on the gas. If i ease my foot off the gas after stepping on it hard it will either stick and I have to put some pressure on it to accelerate again or it will lunge forward. Could this be a problem with my stock BOV? I would have thought throttle body but I cleaned that.

Thx.

1) Unfortunately, coilpacks can get weak but will still pass the resistance test. The only sure way to test coilpacks (again, only necessary for Mkiv TT's with over 100K miles) is to get a known-good coil and swap it for each on your engine.
2) The BOV doesn't have anything (directly) to do with the operation of the throttle body. A quick test to see if there's a problem with your BOV is to temporarily block the vacuum line that opens it. Of course, don't run it up to full boost with it configured this way, but you should be able to do the throttle-sticking test without taking it to full boost.
3) Perhaps the problem is with the throttle cable? Try disconnecting it from the throttle body and ensure the cable slides freely within its sleeve (you may need two people to do this test). Also, check the secondary throttle plate (i.e. the traction control subsystem) to ensure it's operating properly.