TWingo goes off in stand, engine and electronic light

Hello, I’ve been 3 times with Renault now, but they don’t do more than delete mistakes either. My Twingo BJ 2004 1.2 16V always goes out for 2 weeks when I stand still, mostly only when you’ve been driving in a while. Then the engine sign and the electronic lamp lights up and then it has the Macke permanently when stopping or very slow. The dealer, where I bought it, says it can be anything and I should drive until it occurs permanently (??). after Motzerei on my part, that this is probably not his seriousness the suction tube pressure sensor (hope that means so) recouped. After that it was ok a week and now it started again. Was then forced at another Renault dealer next to my job and he said, he taps on throttle valve housing, because that probably occurs very often at the Twingo. There would cost 500 Euro ins.! Nun I have a car guarantee, that would be covered, but must ask my dealer again, because The car guarantee for used cars is dealer-related. I’m afraid now that they say, noööö, we don’t make the throttle valve housing new on suspicion, could also be the wire harness (that could be because it could be. My guarantee actually expires on 3.7.09… Well, now I wanted to ask, how sure is that, that it is the throttle valve housing???