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hi guys having issue with my 2000 civic si 5mt b16a2. I've had p0505 idle air control code for the longest time and idles high and after 10 mins of driving idle starts bouncing at around 1500 and car starts bucking forward when I easing into throttle. Then I have to restart the car to reset it but happens again after few minutes of driving.
things I've tried:
-resetting the code and resetting battery
-checked vacuum lines and even replaced some
-cleaned tb and iacv and intake manifold
-replaced tb gasket and intake manifold gasket
-replaced pcv valve and tps sensor
-coolant flush
-checked spark plugs still good
-replaced battery
-deleted the coolant lines to tb and iacv
-tried adjusting idle screw but didn't help so I turned it back to where it was before
swapping iacv made the idle worse by making it surge from 1000-2000rpm
There is no fast idle valve on this car since it's a 2000
Unplug IACV when it is idling fast and confirm that it drops to less than normal. That means the ECU is commanding the IACV open. On the other hand, if the idle doesn't drop with the IACV unplugged, too much air is getting into the engine some other way such as a vacuum leak or the throttle plate not closing all the way.
Test the ECT sensor with an ohmmeter. A wrong ECT reading can make the ECU think the engine is cold when it is not, and increase the idle thinking it is on a cold start.
Test the ECT sensor with an ohmmeter. A wrong ECT reading can make the ECU think the engine is cold when it is not, and increase the idle thinking it is on a cold start.
A malfunctioning TPS can also cause an idle problem.
Ok so i tried this I unplugged iac and the purge solenoid and it was idling still around 900 I turned the screw all the way in and it wouldn't go down to 450 like stated in the procedure. With the screw all the way in the car idled at 760rpm. After plugging everything back idle is around 1100.
Can't find any vacuum leak even tried spraying all the hoses with soap water could it be a leak inside throttle body from plate not closing completely because I did clean the throttle body recently
The throttle plate must close completely when no one is pressing the gas. The little stop screw is adjusted at the factory so it just touches the sides of the throttle body and it should be left there. If someone has been tweaking it, adjust it back that way and leave it (also recalibrate your TPS after adjusting). Of course the throttle cable can't be too tight, it should go slack when the gas is not pressed.
You should be able to stall the engine out by blocking all of the idle air holes in the side of the throttle body at once. If not, extra air is coming in somewhere.
I adjusted the idle to the lowest point to see if that would help but it didn't. the tps was recalibrated when I replaced it. I loosened the throttle cable already.
when I cover the idle air control hole in the throttle body the idle drops a bit but doesn't stall the car.
Originally Posted by mk378
The throttle plate must close completely when no one is pressing the gas. The little stop screw is adjusted at the factory so it just touches the sides of the throttle body and it should be left there. If someone has been tweaking it, adjust it back that way and leave it (also recalibrate your TPS after adjusting). Of course the throttle cable can't be too tight, it should go slack when the gas is not pressed.
You should be able to stall the engine out by blocking all of the idle air holes in the side of the throttle body at once. If not, extra air is coming in somewhere.
P0505 iacv code tried everything
