Hi all,

Like the title says, I'm experiencing high idle on my FD, it idles around 2k rpm. Once the motor is at operating temperature, the rpm will sporadically surge. Best example I can find of the idle surging is in the YouTube video below. Again, surging is sporadic and occurs for a couple seconds before returning to steady high idle - I am thinking perhaps the high idle issue is related to surging. Is the Idle Control Solenoid gone bad? Or is it worth checking the throttle stop screw? How should this be adjusted if this is the case?

 

Stock ecu or aftermarket, such as Power FC?

Start checking your vacuum hoses, at least the ones you can easily see, including the one to the MAP sensor., mounted on the firewall.

If the ecu is not getting a sensor reading it is expecting, it may cause the idle to move within a default range.

 

Less common but UIM to LIM and throttle gaskets if you don’t find leaking hoses.

 

https://www.rx7club.com/3rd-generati...ncing-1147118/

You have air getting into the engine after the throttle body. It can be a vacuum hose that's popped off, a bad gasket, any number of things. Go through that thread and I think that will help you out.

Dale

 

You can rule out the iacv by unplugging it. Either it will stop doing it or it won't. The possibility of a vacuum leak is high though. A smoke test would make quick work of that. You can also try and choke the engine out. A 2k idle would indicate a large enough vacuum leak to possibly keep it running even with the elbow completely blocked off.

There are still some paper LIM gaskets out there and they do blow out. Check that as well. Its visible with a mirror and flashlight

 

Stock ECU - took a look at the vacuum lines that I could easily see and they all look fine. Didn't get a chance to pull the manifold out yet. Would Idle Control Solenoid cause the surging?

 

Appreciate this link - good find. Will go through it and check.

 

Built myself a little diy smoke canister vacuum leak detector tool - will run smoke test soon. Good call on the LIM gaskets too - probably worth taking out the manifold and replacing both UIM and LIM. Would get a good look at the rats nest too while it's all off.

 

Any link to good reputable replacements? What is the way to go? Metal? Aluminum?

 

oem

 

Dealer should have the OEM gaskets. Otherwise Atkins must have.

Smoke test before digging into the rats nest.

Be aware that pulling the vacuum hoses the wrong way can cause the solenoids plastic nipples to break, then you are in a cascading series of problems.

Are you getting any check engine warnings?

If yes you might want to check what those are signaling.

Did you try unplugging the electrical connector from the ISC. What effect did that have?