The first time driving the car any distance without a/c on, noticed the idle sometimes temporarily dips below normal(~570) and immediately corrects when I go to neutral and release the gas(stick shift). Also now have the service engine light on.

Maybe it does this with a/c on(idle higher) but if it did, never noticed.


Only drove for a few miles like this but noticed no difference in drivability, performance, etc.

I will read the codes tomorrow but can you think of what the problem could be off the top of your head? Idle speed control maybe?

I don't know much about the computerized side of cars generally.

Is it normal for idle to drop below baseline when going to neutral?

If this was just an issue of the idle being low, between 500 and 600, would that be detected and through a code? No stalling, rough running. Everything seems perfect.


The car just passed CA smog two weeks ago so I doubt it's a bad sensor or anything. At least it wasn't bad then.

 

Sounds normal to me, even the 5th gen does that, code is something else I bet that has nothing to do with that.

 

When the AC is on the IACV opens a plunger to allow more air intake which is why it idles higher.

+1

Your idle is right where it should be.

 

Just to clarify, with the a/c off, the normal steady idle is 570 and it dips below 500 when I push in the clutch.

But that still sounds nornal, just the idle is a little low?

Will be back with the codes soon.

 

You guys were right, nothing to do with the idle.

I got:

0304 - knock sensor
0707 - rear O2 sensor

Any idea why they both failed simultaneously?

Is it safe to drive the car a few miles before fixing this? I need to get it to a garage before leaving for a trip tomorrow.

Lucky they held up until I passed smog though

 

The Knock Sensor code you have is what we call a "ghost code" that comes and goes with other codes. Most likely the KS code is trailing the O2 sensor code so you may not be experiencing a problem with the KS.

The function of the downstream O2 sensor is to measure the efficiency of the CAT converter so it has no effect on the car's performance.

After you replace the O2 sensor both codes should disappear on their own within 100 miles.

 

Ghost code, good to know. That makes perfect sense as opposed to both failing at the same time.


And especially since there was no change in drivability, which I would expect if the KS was out.


Thank you guys.