Engine revving problem

If its been without the line for over a year, I Highly doubt it. Look into IAC valve. Most are installed with 2 screws, easy to adjust. Idle Air Control Valve. Look that up, for a start.

PROBLEM COULD BE IN THE DOWN SHIFT SOLENOID.

my engine check light on 4age engine dim before start, will not go off after started and slump throttle black smoke from exhaust

system to lean means that there is not enough gas getting into the system try checking fuel filter and fuel injectors that should help you there hope everything works out

fuel pump? fuel filter? clogged cat? clogged injectors? dirty cap?  dead rotor?  is spark wiring correct? timing right? no idea.  good luck.

I suggest probably hydrocarbons blocking the throttle system. so get the throttle bodies on your ca cleaned, Pour a bottle of fuel system cleaner into the tank and run it exclusively on Shell V-Power petrol. DD tried this and the car ran a lot better.

send your car to authorize dealer to scan the fault,avoiding guessing of replacement of part,ty

your throttle position sensor might me bad or out of adjustment. if it is out of adjustment then it can misfire all the way up to 3500 rpm.
i had a friend that had a miss fire at 2500 rpm. i adjusted the tpss right and the misfire went away. Check for engine codes by jumping TE1 and E1.
Your fuel filter may be dirty and restricting fuel to your injectors.
have your fuel pressure checked.

This possible solution is also weird. I have a '91 Prelude Si also- GREAT car. Do you have anti-lock brake option? If you do, check the fluid level in the anti-lock reservoir. My Prelude did this revving thing twice, and while checking under the hood to see what the heck was going on, I discovered the brake fluid level was very low. I topped it off, and after giving up trying to figure what was wrong, I restarted the car, and no revving problem. I don't know why this is, but it worked for me twice. Countrycurt0

the car is running in limp-mode which is why you can't rev past 2500rpms. what engine did you swap in/