Lude Generation

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?

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Any help on this would be great.

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?

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

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?

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

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.

So when the IACV is disconnected it's fine?

I wonder if perhaps it's a wiring issue?

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

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.

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

Moved to Engine section