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S300 Cold Start Idle

Posted: Mon Mar 16, 2020 2:07 pm
by kraquepype
My car doesn't increase idle at initial cold start - it takes a few minutes for it to go up to the 1200 or so RPM as indicated in the idle settings for a given temperature. It goes down once warm and idles / runs great otherwise.

What could cause this? It should idle high at initial startup right?

Engine is a B16B w/ S300

Re: S300 Cold Start Idle

Posted: Mon Mar 16, 2020 2:48 pm
by Spunkster
It's hard to say without the calibration and a datalog showing what it is doing.

Also what throttle body are you using?

Re: S300 Cold Start Idle

Posted: Mon Mar 16, 2020 7:45 pm
by kraquepype
I can provide that, would you just need a datalog at cold-start?

The throttle body is the stock B16B, 62MM

I went and tried setting the idle according to the hondata instructions, I could not get it to idle under 650RPM with the IACV unplugged. This was with the idle set screw all the way in, so I can only guess I have a vacuum leak somewhere.

With the IACV duty cycle set in the middle, the car would not idle below 1300RPM and would fluctuate.

My drivable settings right now are an idle of 900 with the IACV duty cycle 2 clicks from the left.

TPS is reading 0 off throttle so the throttle position should be good.

Re: S300 Cold Start Idle

Posted: Tue Mar 17, 2020 10:06 am
by Spunkster
You should try to find and fix the vacuum leak first as that could be part of the issue. Do you have any coolant lines still running through the throttle body?

Re: S300 Cold Start Idle

Posted: Tue Mar 17, 2020 11:51 am
by kraquepype
I've checked for vacuum leaks and I can't seem to find any, using the carb cleaner method, checked all over the intake manifold.

Coolant lines are bypassed at the throttle body and IACV.

Also: The idle dips down a bit when I pinch off the PCV valve line. I don't expect the crankcase to be sealed so it seems normal to me but thought I'd mention it.

I'm going to remove the throttle body and check for any blockages, and see if maybe somethings keeping me from closing the idle screw any further.

Re: S300 Cold Start Idle

Posted: Wed Mar 18, 2020 7:33 am
by kraquepype
I was adjusting my valve clearances and found that all my spark plugs were markedly loose. I tweaked the IACV duty cycle and upon cold start it appears to idle at the right RPM now.

Still need to check on setting the idle correctly but I think this has helped.