I've been posting to the FC forum for help on some trouble I've been having with my S5 NA, but nobody seems to have any suggestions. I thought I would open it up to people here as well. Anything you can think of is appreciated as always. I've been working on it and am left scratching my head.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-high-rich-idle-trouble-searched-845243/

 

Hmm. Wow, at least you're very detailed on describing the problems.

You seemed to check out the more common factors that would be causing it rich. Usually it'd be a computer problem or vacuum leak but since that has all come out okay, how are the connections to your coil(s)? Sure, it may not seem at all a feasible solution, but I can't think of any other issues for your running rich, high idle problem.

Usually, high idle IS caused from a vacuum leak. Running rich would be possibly an ECU problem not regulating the air fuel ratio. But, since you've gone those routes anyways, maybe you'll need a stand-a-lone system like MegaSquirt? I could say that FB's are possessed but I don't think getting an exorcist would work. (<---- I had a weird idle issue later on after all fixes were done to cure that problem, then one day it stopped and never showed itself ever, knock on wood.)

How is your fuel pump? Is it fairly new? Any loose connections? I'm going by what I read in the FSM. Or, ignition problems. I'm sorry this isn't much help, you have seen to already gone through a lot of troubleshooting as it is.

EDIT: How about any blown fuses? Is your ECU or IGN (I'm really taking a stab in the dark) fuse possibly blown?

 

There is no chance it is a fuel problem. Fuel pressure is rock steady and I can foul plugs like it's my job. I think the problem really is spark. I have checked the connections to the coils. They do have power, but I think the computer is not sending the signal or a weak signal. I think it must have something to do with the new error code I'm getting.

I agree that the vacuum leak will cause a high idle but I do not believe that my idle problem is caused by a leak, unless you can consider the BAC a leak. It is the sole provider of all air the engine is consuming at "idle". I do plan to pressure test the intake to look for leaks anyway.

This is really maddening. Thanks for the suggestions.

 

I wish I had an answer for you Brian. I want to see this monster perform next weekend at the race.

 

Did your emissions removal include the thermal wax and high idle circuit on the throttle body? If not double check all those adjustments, it took me a while to get everything adjusted right on my S5 T2 swap.
Also the BAC is supposed to regulate idle based on varying engine loads etc, but I don't believe it should be the sole source of air for the engine at idle, even when closed the throttle body should still be letting some air through. You may want to remove the BAC temporarily and see what happens, may help to narrow it down.
Good luck.

 

This may sound dumb, but did you make sure that the fast idle cam is separated from the cam roller when the car warms up? Running rich------How about the secondary throttle plates? Is the thermo switch cutting vacuum to the diaphram after warm-up?

Recently, I had some odd idling issues with my SE (S5 intake swap). Even after warm-up, the BAC was full open and allowing a lot of air in. I noticed that my TPS was out of adjustment. Adjusting the TPS did seem to affect how the BAC worked, unless it was just a coincidence.

 

When I removed the emissions, I took out all of the high idle stuff as well as the thermo wax for the secondary throttle plates, so they are open. The car seemed to run better once I adjusted the tps and that may still be my idle problem. I'm not really sure how the ECU decides to regulate the idle with the BAC, but right now it is very upset.

I'd like to work on more trouble shooting with the BAC and TPS, but at the moment I can't even get the car to start due to this new ECU trouble code dealing with the CAS.

Thanks guys. Keep the ideas coming.