[Newbi] First time poster [Solved], Already I need help Options

[Chanassa]

Hi everyone, first time poster with a keyboard in the other end here, and of course I have a problem.
I got my Celica ST20 1.8 one week ago, a good car and I like it a lot already.
Unfortunately the motor don't run on all four cylinders when it's on idle and hot.
When the motor is cold there is no problem at all, and same goes when I'm revving it, all four is on board and do their workload as they should.
I have found out that it is cylinder number four that is the problem, and tho whole motor have been taken apart and reassembled, we cleaned to cylinders, and pistons (Also the pistonrings, they were stuck and I thought this was the problem) but this didn't help.

I have now bought an used top to this engine, but do you have any tips for what this can be?
Thanks all.

This post has been edited by Chanassa: Nov 25, 2013 - 1:00 AM

[Chanassa]

"Maybe a faulty ECU? Your issue seems electrical to my untrained eyes, since you mention engine temperature making a difference. This makes me think that when the a/f is controlled in open loop and reading from sensors, the error is caused."

- Then it should run on only three when I drive aswell, shouldn't it?

Did try swapping cabels, problem stays on cylinder number four.