Sylvain04

I've a strange problem with my 04 Civic with 162k miles.

When there is a load on the engine (pressing brake pedal, AC on or power steering, ..) and I blip the throttle, the RPM hangs between 1300 and 1700 RPM for 4-5 seconds and then slowly goes to normal (800 ish RPM)

I was suspecting the IACV but the engine idles really nice no up or down.

No CEL, no code,

I'm ready to diagnostic the problem but I'd like to know first if anyone of you had this problem before...

Thanks

lazlong

-Why would you blip the throttle while pressing the brake?

-Does it happen only while driving or will it happen while parked?
-Does it happen when only one load is applied or do multiple loads have to be applied?
-Does it happen if you blip it at the throttlebody?
-Is the throttlebody real dirty?
-Auto or manual transmission?

Sylvain04

I pressed the brake just to test with another load

It happens parked and while driving
It happens with one and multiple loads applied, it is worst when AC is on or when the heater is on (and AC off)
It happens even when I blip from the throttlebody

The throttlebody is clean. I've cleaned it with throttlebody cleaner last week. I also removed and cleaned the IACV which was not really dirty.

Manual tranny

Best example is when I enter my driveway, press clutch pedal, press the brake, turn the steering and RPM hangs at 1500 for many seconds and slowly goes down to normal RPM.

lazlong

Sounds kinda like a vacuum leak.

Let the car idle and push the clutch in, then the brake. Just hit the brake pedal once and let off. Don't touch anything else, just the pedals. If it happens in this scenario then either the brake booster or hose is bad. The hose has a check valve that occasionally goes bad (usually more often than the booster).

Sylvain04

I tried and nothing happened.

I investigated a little more this morning, RPM hangs when heater fan (at defrost position) and AC are both ON. Load on engine (power steering and brakes) just make the problem a little bigger.

BigHec

I say normal.

Sylvain04

Idle hanging between 1500 and 1800 is not normal....

Anyway, I'm just back from Honda dealership where the technician spent 30 minutes checking the problem...For free. He said the problem was the IACV not working correctly even if I cleaned it. Sometimes IAC valves are dirty or defective but not cause stalling.

I'll clean it again and see. If it doesn't work, I'll replace it.

Sylvain04

There are some very cheap IACV on EBay... Are they any good?

http://www.ebay.com/itm/New-Idle-Air-Control-Valve-IAC-with-Gasket-16022-PLC-J01-16022PLCJ01-/281343666361?pt=Motors_Car_Truck_Parts_Accessories&hash=item418163a8b9&vxp=mtr

BigHec

The way you mentioned didn't sound like a long term hang. I've been in cars before that would do things similar to that and everything seemed alright.

Sylvain04

I would say 4-5 seconds at 1500 RPM and another 4-5 seconds to go back to normal RPM

It is annoying when it happens in a parking, turning corners or at stops

lazlong

I would recommend OEM but, $200 is expensive.

Sylvain04

I reclean my IACV and see how it goes before buying a new one.

There are some IACV at 35$ on EBay, not sure how good they are.

Sylvain04

Update for future reference....:

Finally the check engine light turned on and codes were stored in the ECU... P0135 Faulty O2 sensor. Curiously the idle was hanging even if the AC was off and climate control at vent being sure AC was not running.

I replaced the O2 sensor with an OEM Sensor from Honda and relearned the ECU.

Now the idle goes back to normal quickly no matter if the AC is on or OFF.

Here are pics of the old O2 sensor... 260000km