Hello everyone, I would like to start off by apologizing in the case that there is a thread that I am unaware of where OP has the same exact problem and a solution has been made. So, at the risk of coming off as an idiot, I ask you rotary gods for your wisdom.

I bought my RX-7 last year around this time and have been daily driving it since. She has been running well generally, except for a high idle issue(1500 rpm) that I tackled last month by replacing the thermowax and adjusting the fast idle cam. After doing so, the throttle would actually roll off the cam and the idle would come down. Unfortunately the idle is way too low, at 3-400 rpm. Even adjusting the idle screw on top of the throttle body did not raise it nearly high enough to 900 where I want it(FSM say 750 but some ppl say 900 feels better and I kinda agree it sounds happier but lmk if I’m off). To be drivable, I advanced the ignition timing a few degrees which raised the idle, but the highest I could get it without feeling uncomfortable with the timing was 600 rpm. It feels like that was the incorrect procedure(also marks no longer line up with pin) but I am desperate. I’ve even adjusted the TPS to spec but that has not solved the issue.

 

welcome to the board.

first, reset the timing to where it should be.

next, i would start looking for a vacuum leak.

is your BAC present and functional?

https://www.rx7club.com/2nd-generati...w-idle-897504/

 

It is present, but how can I check that it is working?

 

there will likely be a procedure in the FSM. you can get a copy here: Foxed.ca

also, here's a link to another thread: https://www.rx7club.com/2nd-generati...ing-bac-90036/

 

Check this link out, it should be helpful.

https://www.fc3spro.com/TECH/PROBLEMS/EM/bac.htm

 

I checked per the fsm and the resistance was 0.01ohms so I assume it went bad. I ordered a used replacement. I apologize for the late update, been having trouble finding time to work on her. Will update you all once everything is installed

 

no need to apologize. life is life. Rx7Club gets in where it fits in ...

update whenever you can. it's important simply because this thread will come up in a search someday, and someone will actually find an answer/conclusion.

 

Alright, I installed the replacement BAC and started her up and got a 600rpm idle. Decent, decent. I disconnected the BAC connector to see how much impact the new BAC had and it was more than the one I took off(dropped to 200 when disconnected). I forgot that the idle adjustment screw was pretty far out so I couldn’t get her to 750 or 850 like I want. I grounded the initial set coupler and tried raising the idle but there was essentially no change. I disconnected the battery and held the brake pedal down for 30 seconds in case I had to reset anything. Started her up, idle is at 400rpm like before. I got desperate and started tinkering with things like the tps, adjusting it to read 1k ohms per Aaron Cake’s directions. Still a 400rpm idle. The old BAC seems functional, with the resistance reading 11 ohms(I guess I measured wrong before) and it was clicking open when jumped to 12v. I’m very confused now so any help is appreciated.

 

Video of idle after some driving

 

Have you verified you don't have a vacuum leak?

 

I have done what I thought were thorough checks using brake clean. I’d spray around rubber hoses/joints and wait for a noticeable change in idle. I should try again and take more time on it.

 

My suggestions would be to check your spark plugs and wires. Also, check your ignition timing.

 

Plugs and wires are relatively new(maybe 50-100 miles on them?) I will update on the vacuum situation ASAP. Idk if this is helpful info, but on startup, the AWS sometimes(pretty often) doesn’t kick in and I have to pump the accelerator a little cuz the engine sounds rough and below 1000 cold. Still doesn’t start AWS cuz I think blipping the throttle turns it off. Thermowax is new and functional.

 

Did you try adjusting the throttle cable? Just behind the intake there is a cable on like a hook. Follow the cable from the fire wall to the back of the intake It will have to 2 nuts on it. You want to shorten the cable... my 2 cents

 

im having the same problem too.. the only difference is i have the RTek chip mod that disables the Cold - start ceremony. in this case i have to locate the Primary throttle stop screw by the driver side fender over the throttle body and see if that makes a huge difference. if thats not the damn case then i hear the BAC needs a replacement part inside the ECU of my series 5

 

Is yours a turbo? I ask since the only way for me to adjust the throttle stop is by completely removing the TB(haha NA engine go brrr) since everything(thermowax, fast idle cam, and throttle stop) is on the rear of the TB up against the firewall.

 

oh wow man i hope i dont have to do that,, but i did soe TPS readings today


Narrow Range--->Closed---->Results 1.27
Narrow Range--->Full Throttle--->Results 5.25

Full Range--->Closed--->Results 0.95
Full Range--->Full throttle-->Results 4.95

 

Is your idle normal? Also I just adjust the TPS while probing resistance until narrow band is at 1K ohms or whatever value Aaron Cake said

 

after the brush clean & readings i got from a working TPS i only adjusted the BAC adjustment screw counter-clockwise giving more air and made some idle improvements but wont hold idle on its own therfore going to adjust the throttle stop screw =. this is the erratic part of engine going L to lean or R to Rich. for some reason my s5 doesn't show the lettering

 

Hey everyone! It's been a while but I have an update!

I smoke tested the intake system at my school's auto shop and I found two major leaks. One was at the thermowax gasket(I have taken that apart before without replacing it so it isn't alarming that that happened). The second was at the secondary butterfly block-off system(idk what it's called but the system that blocks the secondary throttle butterflies when the engine is cold), specifically, at the bushing that supports the rod the block-off butterflies rotate on. Because of this, I have decided to do the throttle body mod as described on fc3spro. I'll follow their procedure, but I will modify it by trying to retain the fast-idle system as this area gets chilly in the winter.

Additionally, I have found that I was not reading the tachometer correctly. I thought the first line was ~200 so this whole time I thought the idle was waaaay out of spec at 500 rpm when it was actually idling in the ballpark. It was still unstable, but the average was 700-750rpm. In that regard, I apologize for wasting people's time. I'm also grateful for the advice I have been given thus far.