i have an ls/vtec engine with stock gsr i/m and d15 throttle body that i just swapped into a 94 coupe. i had a few check engine lights but read the codes and got them all straight. now when i start the car it idles up to 2000rpm til warm then drops to 1700rpm. i turned the idle screw in all the way and nothin changed. if you tap the gas n left off it drops to about 1000rpm then picks right back up immediately. with no cel n no vacuum hoses loose im lost, any ideas?

 

tttttt

 

Check for leaks in the intake system. An easy way is to spray some brake cleaner around the TB gasket and the manifold gasket. If any gets drawn in, you will hear the engine change rpms.

if that doesn't work, clean the IAC and the fast idle valve.

 

yup! what he said...
also make sure your throttle blade is clean/not sticking and your cable isnt too tight.

 

i cleaned the t/b before putting it on and i used gasket sealer on it because i didnt have the gasket but i have done this before with no problems. and it was a brand new honda i/m gasket but i will check for leaks 2moro. anything else? o n i cleaned the iac before installing because that was one of the cel

 

does the d15 throttle body even have a fast idle valve? n throttle cable is not too tight its not pulling on the throttle at all while idleing

 

If all that checks out, block off the idle port before the throttle blade. If your idle comes down, you have found your air leak! (The IAC may be leaking internally)
Also you could hold up th throttle body to light and see if there is excessive leakage past the blade (can be a problem with cheap aftermarket throttle bodies)

Air has to be getting in from somewhere.

 

ill check iac 2moro but its a factory honda t/b so that should be good. thanks! will update 2moro

 

Double check all your vac. lines, then check them all again, lol. Sucks, but it's almost ALWAYS something stupid

 

anyone have a vacuum line diagram or a pic of lsvtec b18/gsr so i can make sure i have them right? i also have the vacuum line to the bottom of the iab solenoid "t"'d in with the vacuum line to the fuel ressure regulator think thaat is the problem?

 

pyro problem you were right it was leaking through the iac valve i just plugged off the hole until i can get a new one. still idles around 1000rpm but much better than 2200!

 

If at all possible, get rid of that D15 throttle body as soon as possible...it will be a restriction to the motor. Go for at least a 2nd gen B16A TB/B18B TB...they're both 60mm, which is larger than the D15.