Page 1 of 1

Please help with ridiculously troublesome idle

Posted: Mon Sep 30, 2019 7:20 pm
by brynaninja
So.

I have an S300 hooked up to an old '90 Prelude running the original block B21A1.

Don't be scared it's not a civic, my tuner is.

I have done extensive work to the motor and built it as an all-motor setup, big cams blah blah blah high compression, 11:1 blah blah blah..
It has a customized Skunk2 Pro series intake manifold and throttle body on it recently.
Ever since I did the intake mani and TB it has had troubles idling.

Ok, here we go.

The idle is tuned to stay alive during warm-up, now, the air boost valve and the high idle valve have all been removed and it is running Hondata so there is nothing thinking that it is still there.

During warm-up, it sounds like a V8, almost, and is not nice to drive until the ECT gauge moves a bit. Then it idles nicely at about 1000rpm, if you try to turn it down further it gets really lumpy and really tries to die.

The idle air screw valve is in all the way, cannot be tightened further. The idle was set properly with the IAC and the TPS is adjusted properly as well.

Once the car is good and hot, not overheating, the engine fan comes on and around that time the engine idles up at 2000rpm. Way too high. Nothing makes it come down, I am not able to turn it down manually as the idle air screw is in all the way.

The Smanager does nearly nothing. I have adjusted the IAC duty down a bit and this helps but then it makes it really boggy and I have to keep a sharp eye on the rpm so it doesn't stall, usually having to give it a bit of throttle to stay alive. If I do turn it down even one click on the bar, it won't idle on its own to warm up, I would have to keep at least 3% TPS on it.

Why does the temperature have all this control over my motor? I live in a warm climate, the motor is around 18C when it starts, so its not like its freezing or snowing here.

I have attached a photo of my idle parameters, as I have adjusted them, with this setup like this the motor runs high on hot and barely can keep itself idling on warm-up.

Re: Please help with ridiculously troublesome idle

Posted: Mon Sep 30, 2019 7:35 pm
by brynaninja
Bigger shot of it, I realize now it's pixelated.

Re: Please help with ridiculously troublesome idle

Posted: Tue Oct 01, 2019 1:36 pm
by Spunkster
It sounds like a mechanical issue with the throttle body or idle controller as there is nothing different in how the ECU can control the idle controller. If you have large cams then you may have to use a higher idle or it will be very lumpy. It could also have to do with the valve lash as it gets hotter.

Re: Please help with ridiculously troublesome idle

Posted: Wed Oct 02, 2019 2:44 pm
by TTR
Post a pic of the throttle body. Does it have a mechanical fast idle valve on it? What IAC is being used?

Re: Please help with ridiculously troublesome idle

Posted: Fri Oct 04, 2019 1:38 pm
by brynaninja
Yeah it does have some big cams in it, I had it idling nice around 1000rpm before the intake swap. Sounds good there and doesnt want to stall, but since the intake job it has risen considerably. The lash should be within specification, but I will double check this.

The throttle body is the Skunk2 309-05-0040, the one that was sold with the intake as a kit.

The IAC, is not the stock one, as it does not fit on the newer intake, the IAC is off of a H23 from '93, also brand new, and I am getting response out of it. When I go to set my idle mechanically, unplugging it does change the idle and the CEL pops up.

Heres a photo of the throttle body.

Re: Please help with ridiculously troublesome idle

Posted: Mon Oct 07, 2019 8:34 am
by TTR
is the IAC bolted directly to the intake manifold or is it remote mounted? I have run into problems with those throttle bodies in the past. Map sensor is mounted upside down which can cause moisture to build up in the sensor. The port that feeds the IAC air is smaller than an OEM throttle body (I have drilled them out before), they may have changed them since I used one last. Also have had issues with them sticking. Started using S2 Alpha throttle bodies when they came out as they have no issues.

Re: Please help with ridiculously troublesome idle

Posted: Mon Oct 07, 2019 10:52 am
by skaterguy1986
New aftermarket IACV or OEM? I've had bad experience with aftermarket ones, they tend to not really do a whole lot in terms of feeding additional air to the engine. The valve is also more of an idle stabilizer than something that can raise it enough to get the car to fast idle which is why the mechanical wax FITV is there.

Re: Please help with ridiculously troublesome idle

Posted: Fri Oct 11, 2019 3:26 pm
by Gerry
have you taken it back to the tuner to recalibrate the changes made to the intake? drastic changes like usually makes it run differently. remember, it was tuned for the air intake you were using before and not this one. more airflow needs retune and your engine will now suck in more air and if its only running in open loop, the ecu won't help calibrate the changes it probably needs. it could be mechanical but it also could be in the tune since you changed out one of the main components involved in the tune.

Re: Please help with ridiculously troublesome idle

Posted: Sun Oct 13, 2019 8:17 am
by crluver123
can you post the complete calibration file?
I specialize in 3g preludes as a builder and tuner. Feel free to PM me if you want. I'm motoxxxman on Preludepower and honda-tech, Steve Belliveau on facebook.
Also, what cams are you running? How did you get the compression up to 11:1? Have you done a smoke test to see if you have any vacuum leaks? Post a pic or PM me a pic of how you modified the manifold to fit?
Have you made sure the ignition timing is set correctly? By locking the timing from the ONLINE drop-down menu and setting it to 15 and making sure the middle of the 3 marks on the flywheel is at the pointer.
And lastly, when setting the idle mechanically, the engine needs to be fully warmed up, fans and all electrical accessories OFF, IACV unplugged, and service connector jumped (paperclip in both terminals of the two-wire connector in the yellow boot on the left side of the vacuum box).

Re: Please help with ridiculously troublesome idle

Posted: Fri Oct 18, 2019 1:46 am
by brynaninja
Couple pics of it.

Re: Please help with ridiculously troublesome idle

Posted: Fri Oct 18, 2019 1:19 pm
by brynaninja
TTR wrote:
Mon Oct 07, 2019 8:34 am
is the IAC bolted directly to the intake manifold or is it remote mounted? I have run into problems with those throttle bodies in the past. Map sensor is mounted upside down which can cause moisture to build up in the sensor. The port that feeds the IAC air is smaller than an OEM throttle body (I have drilled them out before), they may have changed them since I used one last. Also have had issues with them sticking. Started using S2 Alpha throttle bodies when they came out as they have no issues.
Thanks man, the MAP sensor is on the bottom, but in my car just the vac hose is located at the bottom, the sensor is actually in the vacuum modules container thingy. The IAC is bolted directly to the rear of the intake mani, as specced by S2.

Re: Please help with ridiculously troublesome idle

Posted: Fri Oct 18, 2019 1:21 pm
by brynaninja
skaterguy1986 wrote:
Mon Oct 07, 2019 10:52 am
New aftermarket IACV or OEM? I've had bad experience with aftermarket ones, they tend to not really do a whole lot in terms of feeding additional air to the engine. The valve is also more of an idle stabilizer than something that can raise it enough to get the car to fast idle which is why the mechanical wax FITV is there.
The IACV is an aftermarket one, as the stock ones for my car are discontinued everywhere, and or 500$. The one I have on there is one from a H23 that has matching bolt holes and ports. The IACV has about 40,000kms on it from before the intake manifold job and was tuned perfectly, ran great no issues at all. The car runs rough and rich untill it gets hot hot then starts running high idle. Its fucked up.

Re: Please help with ridiculously troublesome idle

Posted: Fri Oct 18, 2019 1:22 pm
by brynaninja
Gerry wrote:
Fri Oct 11, 2019 3:26 pm
have you taken it back to the tuner to recalibrate the changes made to the intake? drastic changes like usually makes it run differently. remember, it was tuned for the air intake you were using before and not this one. more airflow needs retune and your engine will now suck in more air and if its only running in open loop, the ecu won't help calibrate the changes it probably needs. it could be mechanical but it also could be in the tune since you changed out one of the main components involved in the tune.
The car has been tuned remotely for the new intake, about 4-5 rounds of datalogging and sending it back and forth. The numbers on my O2 sensor seem good and it pulls hard and revs fine. Just has that high idle issue/

Re: Please help with ridiculously troublesome idle

Posted: Mon Oct 21, 2019 12:45 pm
by Gerry
email me the datalogs and calibration file. if you cant mechanically fix it, theres something in the calibration that is off and causing this
and we just don't have enough data on the post to pin point it.

gerryshepherd09@gmail.com