FB - 12A - High Idle, 3K RPM - Holley Intake
 

Greetings,

I purchased a Holley Intake Kit for my '83 RX7, 12A Stockport in 2018.

I finally got around to installing it and firing up my engine last week (been working on everything else beforehand). Unfortunately, no matter what I've done, I cannot get the engine to idle below 3000 RPMs.

I would appreciate any troubleshoots or advice that you may have. Any help would be greatly appreciated.

Some notes on the issue:
1. Timing is on. Car fires right up, and climbs to 3k RPMs like if I engaged the choke on my Nikki. Stays at 3k RPM when at temp
2. The throttle response is great and the RPMs drop quickly when I back off, but do not drop below 3k
3. Idle screw is completely backed off throttle bracket
4. Throttle cable has slack (Removed it during one attempt)
5. I've reseated the carburetor gasket and intake manifold gasket (even tried pb blast around the gasket while running to see if there was a change in idle - no change)
6. I've plugged oil meter port, vacuum advance port, and brake booster hose barb on the intake manifold on different attempts - no change
7. Fuel pressure is set to 6psi with the regulator
8. The primaries and secondaries are not open during idle
9. The engine has been sitting in the car for about two years, empty of fluids, before starting. However, before I started working on the car, It idled fine with the Nikki.

Please see the attached pdf for pictures of the setup. If you see anything obviously wrong, please let me know. I'd appreciate any advice/input you have.

I'm going to be trying new gaskets this week, and if that doesn't work, I'm going to be putting my old intake on to see if I can get the engine to idle back to normal as it once was. If this works, then I think we know what the issue was..

Cheers and thanks for your time,

Vince

Hey Vince. Have you adjusted your idle mixture? If you have access to a vacuum gauge, I suggest you check your vacuum at idle and adjust the mixture.
Hopefully you find the issue soon. Best of luck.

Chimby,

I have played with the idle mixture screws. They were at 1.5 turns before bottoming out (because that's what RB I'm sure "tuned" them to). As I closed them, the idle didn't change, it just eventually cut out due to lack of fuel.

As far as the vacuum gauge goes, I'm going to give that a try soon. Would you happen to know what the vacuum pressure should be for a 12A at idle? I'm seeing all kinds of numbers all over the web.

Lastly, I've never used a vacuum gauge to tune a carb. The Holley I have has vacuum ports for:

-Metering oil to the float bowl
-Vacuum advance port (for trailing ignition only, per RB)
-Brake booster port (intake manifold)

I've read to use the vacuum advance port. However, intuition tells me to test at all of them. A differential in pressure at different ports would tell me that I have a leak between the two.

Thanks again. I will try that this week.

Maybe post a link to this thread or a new post in the 1st Gen technical section, there are a lot of clever carb people there.

​​​​
https://www.rx7club.com/1st-generation-specific-1979-1985-18/

Chimby,

I appreciate the advice last fall. Apparently, I didn't adjust the mixture screws as drastic as I needed to. After running it a while at the high idle, I noticed my headers beginning to glow. I immediately knew it was running way too rich or way too lean. I shut it down, adjusted the mixture screws in the opposite direction, and I was able to get the idle to 1k rpm, which is way better. I wasn't able to get it below that last fall, so I went back to my Nikki for the time being. I'll be retrying the holley carb sometime this spring. The vacuum draw seems to be on per the vacuum gauge, but I'll have to give it another go.


Toruki,

Thank you for that thread location. However, as a new member, this was the only location in which I could post to at the time.