B16A2 Idle problem (intermittent)

**dorikin** · 29-07-2011 09:45 PM

Hey guys

My car has a weird little intermittent idle problem that comes and goes. After the car is warmed up, the idle will go funny and bounce up and down from 200rpm - 1200rpm. This happens for a few minutes before it stabilises itself at around 700rpm. This will also happen every so often when coming to a halt at traffic lights but at other times will be just fine.

The car drives perfectly fine without any hiccups and has not been modified in any way either. Motor is a stock B16A.

I've taken off the IACV and gave it a clean but made no difference.

Any ideas guys?

**dorikin** · 29-07-2011 10:00 PM

I should also note the Malfunction Indicator Lamp (MIL) is NOT on.

**TbM** · 30-07-2011 12:19 AM

Checked for vacuum leaks? If you have an early model b16 you may need to adjust the fitv.

**dorikin** · 30-07-2011 01:21 PM

it's a 2nd gen B16A2..

**beeza** · 30-07-2011 04:24 PM

fitv.

**dorikin** · 30-07-2011 08:20 PM

OBD2 motor - no FITV

**TbM** · 31-07-2011 02:42 AM

Originally Posted by dorikin

OBD2 motor - no FITV

Have you checked for vacuum leaks? is your throttle cable or throttle body plate getting stuck slightly open?

**dorikin** · 31-07-2011 11:48 AM

Throttle cable is fine.. I'll check the TB plate, but if it was slightly open wouldn't that generally cause a higher idle thats steady?

I've had a look around vacuum hoses for leaks but couldn't find any.

I would describe it more as a drop in idle that bounces back up then drops again, etc. Imagine someone putting their hand over your TB which cuts off air and drops the idle to 200rpm, and then takes their hand off which shoots the idle back up and so on.. mine feels something like that.

I'll try and upload a video

**beeza** · 31-07-2011 12:31 PM

It can cause that annoying surging if it's not sealing properly.

The spring on the tb can wear and cause the tb plate not to seal sometimes aswell.

Just make sure the tb cable is adjust properly too..

My friend has had the same sounding problem,I'll ask him

**TbM** · 31-07-2011 03:43 PM

Originally Posted by dorikin

Throttle cable is fine.. I'll check the TB plate, but if it was slightly open wouldn't that generally cause a higher idle thats steady?

I've had a look around vacuum hoses for leaks but couldn't find any.

I would describe it more as a drop in idle that bounces back up then drops again, etc. Imagine someone putting their hand over your TB which cuts off air and drops the idle to 200rpm, and then takes their hand off which shoots the idle back up and so on.. mine feels something like that.

I'll try and upload a video

Its my understanding that if your rpm is too high when your idleing your ecu will cut the fuel untill the rpm drops, then when it reaches a lower rpm it will turn the fuel back on which will repeat the cycle. This can be caused by too much air getting into the engine weather it be from a vacuum leak, improperly adjusted idle screw, TB plate not sealed etc

If you have ruled out vacuum leaks and you have checked your throttle body is sealing properly i would probably test the IACV next and make sure its still functioning properly.

**dorikin** · 31-07-2011 05:07 PM

I adjusted the idle speed today following the FSM instructions.

With IACV disconnected it was idling at 200rpm, so increased it to 450-500rpm by adjusting the idle screw which equates to roughly 750rpm with IACV connected

But still hasn't fixed the erratic idle. What is the best way to test the IACV?

Also got some readings from the TPS. 0.5V closed and 4.6V WOT.