i just bought a 99 civic si. When I crank it up it revs all the way up. I changed the IACV, and map sensor. but it still does it. there is a round two wire plug(green&black) left of the dist. does any one know what it goes to.

 

think its the oil pressure sensor for the vtec solenoid

 

How many RPM is all the way up? 9000? The revving issues could be several things. IACV is one, which you replaced. Check the following: Vacuum line leak or throttle body gasket is bad. Does the throttle surge or just hang at xxxx RPM? Could be the idle adjustment screw also

 

if i let the car sit for about an hour. it will crank up and surg between 1000-2800 rpms. after it runs for a little bit and i cut it off and re-crank it, the rpms will redline.

 

Holy crap... I'm going to take a couple guesses: your throttle position sensor is busted, your throttle cable is stuck, you have a serious wiring issue, or your computer is faulty.

I've never heard of a Honda computer red lining the car on startup... I would very much like to witness this event.

 

i unplugged the tps and the throttle cable is not stuck. the only code is a coolant sensor code. but i think that would cause my problems.

 

it still revs up with the tps unplugged

 

Check the tension of the throttle cable at the throttle body. Is it holding WOT?

 

Check the color codes for the wiring to the harness plugs that they go to the right sensor, ,they might be mixed up(IACV,IAT Map etc or the one that goes to the ps rack mixed up) use a Helms or other reliable schematics well at least thats where I would start.

 

I have checked the cable. the owner before me put a b16a3 engine in the car and said he swapped everything over from the a2 engine. but I am wondering if he put the a3 and wiriing harness from the delsol into the car. if so, would the p2t ecu, running an obd1 engine cause this

 

Thread titles MUST be subject specific so that members browsing topics can easily understand the tech problem without reading the post -- title edited.

 

First fix all your engine codes. Once the computer stops complaining then diagnose unwanted behavior.

 

Sounds like maybe the intake manifold is cracked or the gasket is leaking

 

i finally fixed it. when they put this aftermarket intake on it, not only did they mess up the gasket, they didn't even put they nuts on the bottom of the intake..