Rb20det high idle

[S13gts-t]

Please help me friends. At my with end. Have torn this engine down and rebuilt with all new seals and had cylinder head machined. I finally have the engine firing on all cylinders. Sounds smooth as butter. Only problem is. My idle won’t go below 1800.

here is what I have tried.

adjust idle screw all the way in(closed).  Blocked off cold start valve(1600 rpm),  Adjusted cas. Pinched each hose leading to the intake manifold to see if there is a change in idle(no changes). Cannot hear any vacuum leaks.

known problems are that the manifold gasket that is between the upper and lower parts of the manifold has a tear in it(not very big, definitely not enough to idle at 1800rpm).                            No o2 sensor connected right now(don’t think it would change idle a lot, maybe I’m wrong?)

 

[GTSBoy]

Spray carby cleaner around every place where air could leak in until you find it.

[BK]

On 13/08/2021 at 9:53 PM, GTSBoy said:

Spray carby cleaner around every place where air could leak in until you find it.

Absolutely. Pinching hoses doesn't really rule it out. With the vacuum booster hoses they are quite firm, so you might think you've blocked it but really you haven't. Spray method really is gold.

We found a high idle as described above with it recently that progressively got worse until idle was 2000rpm - aac screw right in, no pressure test observable leak etc. Turrned out to be a 32 faulty clutch booster, which is nice since they are a $500+ item now 😒

Use the spray, you'll find it👍

[S13gts-t]

Appreciate the replies. I’ll put it back together this weekend and try it

[S13gts-t]

Doing more research. Maybe my idle is fine? This Rb is in my s23 with stock gauges. Would read higher due to having 2 more cylinders?

[Duncan]

Hard to be certain, but probably not. In an olden car that uses coil triggering for the tacho maybe but s13 should use ecu's rpm which comes from the CAS, not coil firing events.

My money is on an air leak, most likely a vacuum hose is not connected properly at one end or the other, or has a split in it.

[blind_elk]

On 8/14/2021 at 1:00 AM, S13gts-t said:

Doing more research. Maybe my idle is fine? This Rb is in my s23 with stock gauges. Would read higher due to having 2 more cylinders?

Does the engine sound like it's idling too fast? The difference between 800rpm and 1800rpm should sound obvious.