[Bob Lincoln]

It should do this just a little, the computer causes this to happen so that it won't stall. But 3000 RPM would be too much. Does it happen when you stop and idle?

This could be a vacuum leak - a split in a hose or the throttle body gasket leaking.

 

[Seba]

No, when idle RPM is about 800, byt if I even gently touch acceleration pedal it's increasing fast to 1300, and comes down slowly. Too slowly, I think. I've checked fault codes, there aren't any except P 1684, but it's because the battery was disconected not long ago.
Thanks for suggestion, I try to find any vacuum leaks.

 

[ImperialCrown]

Or a sticking IAC? This may not set a fault code. The throttle body blade/bore/passages should be free clean and of carbon build-up.
At an idle if you unplug the IAC (this will turn on the 'ck eng' light and set a fault code that can be erased later), see if it still exhibits the same racing idle when bumping the throttle. Wiring harness and connection issues may also cause IAC problems.
The TPS potentiometer signal voltage must also track throttle opening/closing smoothly and evenly.
An OBD II scan tool sensor values screen may display a reason why the RPM's are hanging on longer than they should.

 

[Seba]

IAC? Is it the idle control engine/valve? I've tried to unplug it (It sets fault code P 0123), but it didn't help. I also check the hose placed on PCV valve - it seems to be ok.
I have possibility to change parts between my and other engine, but the other one is taken off from the car and I'm not sure if everything is in order with it. Besides, I don't know which parts could be responsible for this strange problem.

 

[ImperialCrown]

It does sound vacuum (leak) or throttle body related. If you pinch off the power brake booster vacuum hose with blunt pliers, does it affect the return to idle at all?
Is it the correct PCM part number for the car (there should be a label underneath)? Have you owned it since new and did this revving problem happen all of a sudden?
Did this problem happen after any kind of service or part change?
Is there any binding or sticking in the throttle return linkage at all and does the throttle blade snap shut when released?

 

[Seba]

Well, the problem is fixed :thumbsup: . There was a vacuum leak in the intake manifold (or collector, I don't know exactly how to call it). The throttle is fasten by two screws to the engine, under one of them is also some kind of metal plug with gasket in the intake manifold, and there was a leak.
So thank You very much for help .

 

[ImperialCrown]

I'm glad that you found it.
What led you to find it? Was there a 'hiss' noise from the vacuum?

 

[Seba]

No, I replaced the intake manifold (I had one from the other engine), and when problem disappeared I started to looking for leak.
By the way: when I dismantled intake manifold, I plugged these four throats, which lead air mixed with fuel to the engine. I did it to prevent any small things like screws fall into the engine, and I stuck crushed pages of newspaper there. I forgot to take them out later, and one of these was sucked inside, when I started up the engine. I thing it's already burned and excreted by exhaust, but could it make any seriously damages in engine? So far the engine seems to be healthy, there are no noises coming from cylinder head, and I didn't notice any distressing symptoms.
I know I should have been more careful, but now it's too late. I was lucky that it was only a newspaper, not a rag.

 

[ImperialCrown]

If the paper passed through and burned, you should be OK. I think that any damage symptoms would have been immediately noticed. Ash may further be burned at the catalytic converter.