Bouncing Warm Idle

BMCC · Post by **BMCC** » Thu Feb 09, 2012 9:40 pm

I said this in JayJays thread but happy to say it again. If you look at the diagram for the throttle body you will see the lower hole is where the FITV draws its air from. The upper hole is where the base idle screw and the IACV draw their air from. If you get the car warm and put your finger over the lower port hole it should not be drawing in any air. If you put your finger over the Upper port hole the car must stall unless it is drawing air from another source. So I would pull the Idle air control valve and see what happens to the revs as it should return to base idle (about 550 rpm when warm). If not then someone may have tampered with the idle adjust screw or you are drawing air in from somewhere else. Go round all the gasket areas with some carb cleaner and see if the rpms drop (be careful though as it is flamable).

edit: what happens when you pull the IACV (original 4G one) does the rpm stop bouncing? Stablize at 1200 or so rpm?

Post by **Ammo** » Thu Feb 09, 2012 9:48 pm

+ Rep

Buzzonion Vtec · Post by **Buzzonion Vtec** » Thu Feb 09, 2012 10:29 pm

Ok two things to suggest here but setting these throttle bodies up to be 100% is very much a feel and experience thing. Even if you follow the letter of the manual it doesn't always work due to wear and tear of the components.

From what I could see (and hear) in the video when you put your finger over the lower hole for FITV there was some suction through that hole which would indicate that the FITV is still open a little allowing air to bypass the throttle plate. The ECU is "seeing" this increase in revs and is dropping the duty cycle of the IACV to compensate. This then drops the revs to below "expected" levels so ECU is increasing IACV duty again and so the cycle continues.

If holding your finger over the FITV hole has no effect on the idle (hold finger there and give it a blip like you doing in the vid to get it to bounce) and you have no other air leaks you should go ahead and carry out a throttle body set up.
Sometimes this is just simply an adjustment of the idle air screw at the top of the throttle body but sometimes this will also include an adjustment to the throttle stop to compensate for wear.
Warm engine up and switch off.
Bridge service connector and disconnect IACV
Start engine - you may need to hold the throttle a little - adjust idle screw until you have 550-600rpm. Switch off engine, reconnect IACV wiring and disconnect service connector. Start engine and allow to idle without throttle for a while . This is the basic idle speed setup procedure but like I said you may also need to make an adjustment to the throttle stop screw - If this is required then it only needs tiny adjustments so don't go mad with it.

Rich

2lude · Post by **2lude** » Thu Feb 09, 2012 10:38 pm

I would say re bleed your coolant system as some air locks can be a nightmare I had to bleed mine 4 times to get rid off all the air

Screw that rich posted as I was follow what he said

Post by **Merlin** » Fri Feb 10, 2012 9:01 am

Awesome info, thanks to all. I will give it a try.

PerformanceAutoworks · Post by **PerformanceAutoworks** » Fri Feb 10, 2012 9:48 am

I meant to say this last night but if this is for your track car personally I would remove the FITV altogether anyway. Remove it and blank the underside of the throttle body with an alloy plate (use sealant where the o rings would normally sit). Only slight downside can be a low idle when very cold but some throttle body setup can compensate this to certain degree. For track cars I prefer to run the idle a little higher than stock as it helps keep the idle oil pressure up a bit when coming of track with a stonking hot engine.

Post by **Merlin** » Fri Feb 10, 2012 10:16 am

Thanks for the suggestion but I'll leave the FITV on as im only running the H22a2 for the summer. I have an H22a7 sitting here waiting to go in

. Im assuming the a7 has a FITV as well so I will keep that mod in mind.

PerformanceAutoworks · Post by **PerformanceAutoworks** » Fri Feb 10, 2012 10:36 am

No the A7 doesn't have a FITV at all so assuming you are using the A7 intake manifold and throttle body you'll no longer have a FITV anyway.
It'll take you as long to remove the FITV, strip, clean/adjust it as it would to knock up a quick alloy plate and delete it altogether. That's really the way to go...especially on a track car

Supercharged 無限MUGEN BB1 Profile · Post by **nucleustylzlude** » Fri Feb 10, 2012 10:54 am

Info FTW /\

Mine's going.

JayJay · Post by **JayJay** » Fri Feb 10, 2012 11:04 am

Should probably leave mine, as it's only really a road car

That idle screw adjustment sounds like it should sort my problem out as well, I'll have to give that a shot.