Motor: 94' B18C1

Problem: I turn on the car first thing in the morning and its idling around 2000rpm sometimes a little higher. when it reaches operating temparature it idles up to 2000 rpm then it drops down to 950-1000rpm and back up to 2000rpm constantly. annoying as hell and I would like to fix it.

Trouble shooting: I checked the ecu and it threw code 14. I replaced the IAC valve and reset the ecu and no more code, but the idle is still the same. Due to a tight work schedual I haven't had time to look at everything. I am assuming it might be vacuum lines, or the PCV valve but I would like to know what other issues will cause the idling problems. TIA.

 

clean the IAC valve and check for vacuum leaks. also try adjusting the idle screw.

 

I replaced the IAC valve with a brand new one, I am in the process in looking for vacuum leaks. But just for a list of possibilities, what are some causes for idling problems?

 

map sensor, cracked intake manifold, poor tuning(ecu)

 

Thanks for the input. I bought the car with the motor swapped in it from my cousin, no tuning was done to the ecu. A bad PCV valve will cause bad idling correct?

 

yes, try the pcv valve

 

check your tps sensor also.

 

I checked the PCV valve, I notice one of the hoses was split so I replaced it. I also shook the PCV and it rattled, so its still in good condition. Idling problem still exist.. would a bad/faulty TPS throw a CEL code? I so, I have not codes being thrown. What should be a next step to trouble shoot my idling problem?

 

try another car ecu

 

does anyone know what internal problems will lead to idle fluctuations? camshaft, cam gears, etc. ?

 

https://honda-tech.com/forums/honda-prelude-4/end-all-idle-surge-bounce-etc-problems-thread-1979500/

 

Don't the 94s still have the FITV under the throttle body? That would be the first thing I check.

 

When the idle was bouncing around, I covered the lower hole inside the throttle body, and it still bounced around. Then I covered the upper hole and the bouncing stopped and idled at 1500 rpm.. any input?

 

BUMP. Also, would the MAP sensor be a source of the problem here?

 

BUMP

 

I replaced the FIT Valve, and the problem still exist. Can anyone on HT give me any pointers?