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I swap the BPT engine on my '94 MX3 (DOHC) but my rev are high (at aprox 1600), what I need?

Hrmmm

Okay we need to get some more detail form ya.

Is it you have a high idel or is it that tacometer is no longer suited to what you need

Ok, my car is accelerated and the rev are unstable, they are at 1400rpm and the goes up to 1600rpm and then goes down to 1200rpm, and so on (all this without running the car, of course). Any idea?

Okay so let me see if i understand your question

While not pressing on the gas petal with your foot the RPM of the motor will go up to e 1400 to 1600 then back down to 1200 and keeps going all over the place while not stepping on the gas pedal?

Thats right torpedan...

did u check to see if ur o2 secor is still good and make sure ur vavum hose is conected to your intake my car did the sake thing hope this helps

There are sevral things which can lead to this problem. My personal advice is to have a professional mechanic check it out.

As stated vaccum leaks or a bad 02 sensor can cause idel problems.

Also the idel control vaulve, and throttle body coolant system can cause problems like this too