I did search but mine is a bit more detailed：Installed a new IAC valve on stock d16y7 after a P0505 code, bleed the system, then engine idles at 1500 when warmed up, then P0505 comes up again, looked for loose connections then I cleared it, here is whats interesting: after clearing the code the rpm is still at 1500 but very steady, after about a 10 mile drive, i stop and let the car idle, within 10 seconds the P0505 CEL comes up again and immediately engine idle starts sounding rough, I tried this a couple time already and it goes in this cycle every, single, time. someone please help, appreciated.

 

Its unable to perform as it should and I hope you used a 'new' and not a 'new to me' part. I'd check around for any loose vacuum hoses.

 

i did, and i also plug in a scanner and the vacuum reads 22 steady, does that mean thete is no leak? oh and the car starts to shudder violently after warming up, its not engine vibration kind of shake but a full on back and forth rocking motion when applying throttle

 

Just wondering if this part on the iac valve needs to be adjusted, it seems like its got some roon for rotation.

 

Anyone?

 

Ohm test the ECT sensor.
Check the input reference voltage and output voltages from the TPS.

 

Thanks for the input I will, but will a bad ect sensor trigger a p0505 code? because as soon as this cel came on the engine starts acting weird

 

I think the egr is the problem since all the problem only starts after the engine is fully warmed up and the egr valve seems to be the only part that starts to operate wgen the engine is warm. is the egr valve on 98 civic vacuum or electronically controlled, if its vacuum control will a vacuum leak cause it to malfunction?

 

but I still don't get why the P0505 keeps coming back up

 

Yes

The D16Y7 does not have an EGR system.

 

Got a new ECT sensor today, nothing change, all symptoms still exist, and now the car revs to 2k enerytime the clutch is pressed, this used to happen rarely but now its every single time

 

could it be the injecters getting clogged when i let the car idle, causing a misfire and the jerking? but im confused like why does it only occur when car is warmed up and why is P0505 cel keep returning instead of a misfire cel?

 

Get a multimeter and use it to test input and output TPS voltages.

 

get a dmm.
check for vac leaks.
and yes check the tps.

 

I did check the tps it was fluctuating around 4.9 and 5 at rest and went up to 4.6 smoothly, i was wondering where the hole in the pic below goes, because i think some tb cleaner got in there while i was cleaning the throttle body, will that that be the problem?

 

It's the idle screw air bypass hole.

When the engine is warm and idling high, use you finger to cover this^ hole or the other hole leading to the IACV.

Does covering one of the holes cause the idle to drop substantially?

 

I cover the hole in the picture and it droped from 1600 to 1400, not significant.

 

What about the other hole?

 

Forgot to check, the weather was cold for the last couple of days and the car did't act up, so im guessing it only happens when its hot and as soon as rad fan kick in the car starts doing weird stuff.

 

just checked the other hole today, rpm droped to the normal 750 and engine sounds normal as soon as i cover the hole

 

Start by properly calibrating the TPS to read 0.5V at closed throttle. Then follow the service manual procedure to adjust the idle speed.

 

does that mean the iac valve is not the problem?

 

(d16y7)
Recently started having this problem: whenever I press the clutch in, whether its shifting gear or coming to a stop, the engine would rev to around 1700 and stays until the car comes to a complete stop then it will drop to normal. once the car is sitting still though, the rev stays normal no matter how many times i press the clutch
No surging, no sticking throttle cable, tps, iac valve, vac leak all checked no problem, any ideas?

 

you plugged the inlet port of the IACV while the engine was running and it shut off?

 

Clean the throttle body with brake cleaner, and adjust the throttle cable to have some free play (~1/2").