Subaru impreza 96 cannot start when cool engine. when i try to start by press throttle sound engine knock.but worm engine start easy.

Here is a list of Subaru diagnosis codes. If these are not what you are coming up with let me know the numbers you are getting and I will look them up on my genisys scanner to further assist you.
1111 No codes stored
11 Crankshaft position sensor (Don't confuse with above, usually when the crankshaft sensor if dodgy the thing won't start anyway)
12 Starter switch faulty
13 Camshaft position sensor
14 Injector no.1
15 Injector no.2
16 Injector no.3
17 Injector No.4
21 Engine temp sensor
22 Knock sensor
23 Mass air flow sensor
24 Idle air control sensor (usually accompanied by running too fast/slow)
31 Throttle position sensor
32 O2 sensor
33 Vehicle speed sensor
35 Emissions canister purge valve
38 Torque control signal (Automatics)
42 Closed throttle position
44 Turbo wastegate regulator malfunction
45 MAP sensor
49 CO adjustment resistor for older cars not fitted with cats
51 Neutral switch (Manual gearbox)

I had a similar problem in 96. dealer replaced knock sensor and another sensor but it happened again on way home.

Obvious issues of course are plugs and spark plug wires. Eventually solved my issue by replacing all vacuum hoses and putting clamps on them. A very small vacuum leak was causing this. It was more prevalent under load (going uphill for example) and when cold (just started)

location of knock sensor on 1997 impreza

Ince you purchase it you will find it for it is the only item that will match the part. It will be located on the manifold by the throttle body area

Could be many different problems. Fist one that comes to mind if you have alot of miles is just oil and filter needing replaced or oil too thin. The other problem could be piston slap which occurs when you have a lot of miles and wear on the sleeves is past recomendation. It allows the pistons to rattle a bit till the heat takes over and straightens them out. Usualy consumes s fair amont of oil when this is the problem. Hope this helps and feel free to add more coment to the problem if you don't think these are the problems and we will see if I can suggest something else.

hi mate try a thicker grade oil i'm not an expert on the turbo charged horizontaly apposed engine ...but i take it you are not the first keeper of the car so its probably had the wotsits raced out of it and seeing that its around the m reg it stands a chance age and the odd boy racer are unfortunately against it as i beleive that year was the first of the impreza ...try a 15 or a 20/40 oil failing that take the air intake pipe off and checkfor oil you will get a degree of oil in the pipe but not bucket loads good luck !!

try adjusting the throttle cable, its a case of loosening a nut, pulling the cable through a bit more and then tightening it back up, you find it on the right hand side of the engine block close to the exhaust manifold.

Jayce

Sounds like warped fly wheel.

directly below the throttle body on the drivers side of the engine block. Has a white connector attached to a single black wire lead. I had to remove the black plastic piece that connects to the throttle body and the air filter housing, in order to see/get at it. Easy fix once you find it. Haynes manual shows it in a different location, so don't confuse yourself looking at the diagram.

check your rear break. probably needs break pad.