Does anyone have any specifics on how it works, what time everything engages, and whatnot, on a s5 t2? Also, the butterfly, when it opens, does it cause a rich/lean situation?

 

when the car is cold the thermowax can enguage the fast idle cam and that bumps the throttle plates open enough to give you a 1200-2000rpm cold idle. as the car warms up the wax retracts (i think, it could extend, i donr remember), and the idle will drop until the fast idle cam disenguages and the idle drops to normal.

on an fc the secondary "choke" butterflies are hooked up to a vacuum thermal valve, that can suck the plates closed until the coolant in the tb warms it up enough to turn it off and then they open.

the aws is basically a big airvalve, that dumps air into the motor to get 3000rpms, on an s4 it triggers when the switch in the bottom of the radiator is "cold"

mike

 

so hypothetically, if the wax rod overextends, what would happen?

 

i forget if it extends when its cold or retracts when its cold, but it will either be stuck on the fast idle all the time or never go into fast idle, depending on which way it goes

mike

 

Would the upper idle limit be reduced if it's missadjusted...? (ie, can't RAISE the idle past 600RPM @ using BAC)

 

The thermowax only increases idle speed to 1000-1200rpm. If the engine's cold at start-up the AWS solenoid and the BAC valve combine to increase idle speed to ~3000rpm for 15 seconds.

If the thermowax is out of adjustment, it can hold the lever on the fast-idle cam even the though the thermowax rod has extended (engine is warm), meaning the idle stays high. I had this problem recently and fixed it by removing the TB and following the adjustment procedure in the FSM.

I also had a bit of a play with the TB while it was off the car. By alternately running hot (boiling) and cold water through the TB coolant connections I could watch the thermowax in operation opening and closing the throttle. Once you understand how it works, it's easier to figure out how to make it work properly.

 

No, the thermowax can't lower idle speed, only reduce it. Once the engine's warmed up and the lever falls off the cam it has no effect.

 

have you tryed to use the throttle stop screws to rasie the idle? I would try that if you BAC is maxed out.

 

if the bac screw does nothing = bad/ non working bac?

mike

 

Does his TII have that 'sealed' adjuster screw by the boost sensors (yes, I know it's called something else on the TIIs...) The point being my own mechanic had a hell of a time setting the idle on his 85 GSL-SE until he finally opened up that screw and set it so that he got the idle he wanted. I'm considering this myself, as I now can't get my own idle below ~900revs...

 

FC's have those too. It's for adjusting the idle mixture.

 

Well, I knew that 13Bs have them, but not if the s5 tIIs do. I'm an NA guy.

 

only the S4's have them. both N/A and turbo

 

Hmm... i dunno, i'm at a loss. I need to pull the tb off soon anyway... want to replace all vac lines... but i'm just getting more and more frustrated with this goddamn car.

So wait, if the thermowax dealy can't lower idle, how come when i turn the screw that it pushes, the tps changes value? I have to re-adjust the tps? Doesnt that entail the throttle plates opening? Wouldnt that affect the idle, no matter how hot/cold the car is?

Thanks
-Ross

 

Idle your car til fully warmed up. Now pull the bac plug off. Normally the idle will decrease just a bit. If nothing happens when the plug is pulled off, check the bac to see if there is a ground signal from the ECU.

Adjustment of the thermowax, fast idle screw and cam is in the Fuel section of the free online fsm at http://www.iluvmyrx7.com

In your case I'd suspect the whole throttle linkage is out of adjustment and you should go to the above site and adjust it from scratch.

Yes, series five do not have the variable resistor to help adjust the idle.

IF your car does the cold start thing in the morning i.e. approx 3000 rpm for 15 seconds....then the bac is working for sure and you don't have to worry about checking it out. If you have not had the 3000 rpm startup in the last few weeks/months...then I'd suspect the bac has a problem.

The following is a good read for idle problems. It was written for a series four, but still applies. http://www.teamfc3s.org/info/articles/idle.html

 

Found this in my bookmarks:

https://www.rx7club.com/forum/showth...67#post1603367

BAC/ECU fix:
https://www.rx7club.com/forum/showth...threadid=79636


Good write-up on checking the BAC:
https://www.rx7club.com/forum/showth...hreadid=116449