Bouncing Warm Idle

Post by **Merlin** » Thu Feb 09, 2012 11:18 am

I would like to try and get this sorted once and for all as im using this engine over the summer.

My 4G has had a bouncy warm idle from when I bought the car. It idles fine when cold but once warm it bounces from between 800rpm and 1200 over and over.

I bought a 2nd hand IACV (it was stamped beginning with a "B" while my orignal one was stamped beginning with a "A". Swapping these over did nothing to solve my idle, in fact on the first bounce the revs went over 2K than bounced between 800rpm and 1200 - 1500rpm.

I pulled the IACV out of my H22a8 5G and swapped it onto my 4G. The IACV off my 5G was stamped stamped beginning with a "A" but had different characters after that. This IACV is 100% known working but dint stop the idle bounce. With this IACV in place I pulled the power connector to the IACV and idle returned to sub 1K warm idle

I have clean my FITV, a bit of carbon build my but nothing serious IMO. My throttle plate is freely moving, I clean it out as there was a load of black crap. I ran out of time to try and see any cracked hoses (non look split from a first glance). What hoses should I check in detail? Or any other ideas?

[youtube]wwm0-tlsNHk[/youtube]

Any help on this would be great.

JayJay · Post by **JayJay** » Thu Feb 09, 2012 11:20 am

I haven't got sound here, but what happens when you block the upper and lower holes? Do the revs stabilise at all on either of them?

Post by **Merlin** » Thu Feb 09, 2012 11:30 am

Upper (IACV) revs drop and would stall the car if I left my finger on their long enough. Lower (FITV) nothing happens.

The revs seem to be fine when I pull the IACV electrical connector

Post by **Ammo** » Thu Feb 09, 2012 11:48 am

It's odd you have to rev it again to get it to bounce.

Been a while since I've had the issue so i'm a bit rusty.

Car stalls so I'd say there are no vacuum leaks, is the coolant bled correctly?

JayJay · Post by **JayJay** » Thu Feb 09, 2012 11:49 am

Odd. So when the IACV isn't on the revs are fine. It *must* be the IACV or something connected to it.

Post by **Merlin** » Thu Feb 09, 2012 12:02 pm

Yeah coolant is fine, it was one of the first things I checked. The bliping of the trottle to get it to bounce again was an isolated issue. When you drive it, it always bounces.

Yeah I concluded it must be IACV but cleaning it or swapping it out didnt solve it

I dont know where to go from here.

JayJay · Post by **JayJay** » Thu Feb 09, 2012 12:07 pm

So when the IACV is disconnected it's fine?

I wonder if perhaps it's a wiring issue?

Post by **Merlin** » Thu Feb 09, 2012 12:08 pm

Ammo can you move this to the propper section for me, Doh!

Roystan · Post by **Roystan** » Thu Feb 09, 2012 3:18 pm

I too would like help with this.

I have the same issue but mine bounces from 1000rpm to 1800rpm on warm idle. Its just started doing this too, out the blue.

Revs drop when the clutch is pressed - is this the same with you Merlin.

Post by **Ammo** » Thu Feb 09, 2012 3:58 pm

Merlin wrote:Ammo can you move this to the propper section for me, Doh!

Moved to Engine section