I've been running my s5 NA without the thermowax hooked up ever since I had the motor rebuilt to race in ITS. This weekend I decided to hook up the heater core and the thermowax since cold weather is coming and I'm sick of having to work the brake and gas until the car is warm enough to hold idle by itself. However, I failed in gettign the cold idle assist hooked up. I'm not sure how the system works and couldn't find it in the factory manual, so I just reran the coolant lines up to the throttle body and hooked up the vacuum lines to it. Originally I had the vacuum source on the outer nipple, but it was just sucking air from the end of the thermowax resulting in a vacuum leak and rough idle even when warm. So I ended up swapping the vacuum source and the line running over to the choke diaphram on the opposite side. That solved my vacuum leak, but the diaphram still isn't activating the choke plates when the car is cold. Can someone give me a rundown on how the system works, where to find it in the manual, and perhaps shed some light on what I'm doing wrong?

 

hmm im not sure how to help you with that problem but if you go to rx7city.com they have the full service manual but good luck

 

You've got the double throttle system and the fast idle cam mixed up. The double throttle system operates the No. 2 secondary butteflies, the ones that are downstream. On manual transmission cars those plates are held closed with the vacuum diaphragm until the engine gets up to temperature. Then the hot coolant makes the thermovalve (thing with two nipples on it) mechanically cut the vacuum signal to the diaphragm. This function is controlled by a solenoid valve on the 3rd gen cars instead of the thermovalve in the FC.



The fast idle cam is linked to the primary throttle valve. There are no choke plates. On an unmodified throttlebody, the fast idle cam will hold the throttle plates open unless the hot coolant is supplied to the thermowax element inside. The thermowax element is similar to the way a thermostat works: hot coolant causes expansion and makes a rod extend. On a thermostat, the extension of the rod allows coolant to flow to the radiator. On the fast idle system, the extension of the rod rotates the fast idle cam to lower the idle.

The coolant supply to the fast idle system lowers the idle. It does not raise it. A completely stock throttlebody without the coolant supply would idle high. That's why owners physically remove the fast idle system in the TB when they eliminate the coolant hose; if they didn't remove it, the throttle plates would not close to their normal resting position. Mis adjustment of the various TB screws can cause funky symptoms too. There is a screw on the fast idle cam that can affect its behavior.

 

Thanks, arghx. That's what I was looking for. I actually haven't done squat with the thermowax, so I'm ok there. It's the double throttle system that I'm trying to get operational. Apparently something in that system is dead, as I have it hooked up right according to that diagram, minus the vacuum delay valve. However I'm still having to work the throttle when it's cold to keep it alive.

 

If your car is like my car, you will find that the double throttle diaphragm does not hold a vacuum and therefore will not close when it should when the engine is cold. This indicates a leak inside the vacuum diaphragm, apparently a common fault. I tried to get a replacement from a auto dismantler, but it was little better than the original. I am having mine cut open as we speak to see if I can repair it internally.

You can check this per the FSM procedure (look up double throttle diaphragm). The check is basically to disconnect the hose leading to the diaphragm, and hook up a mityvac to it, and pump it down to 18" or so of vacuum. You should see the plunger retract into the body, and it should hold vacuum (not leak down).

If that works, the next likely place to look is the thermovalve, located on the back side of the intake manifold. It is a temp operated valve that allows vacuum to go to the diaphragm under cold conditions (warm up), and then once at operating temp it closes off the vacuum supply and opens the circuit going to the diaphragm to ambient air pressure.

The delay valve is supposed to be there so that the #2 secondary throttle plates (which I think you are calling the choke plates) open slowly upon sudden application of heavy throttle when the engine is cold. This keeps the engine from faltering upon sudden throttle increase when cold. Without the delay valve, the #2 plates will lose their vacuum almost immediately upon sudden throttle increase, so they will open immediately, and defeat the purpose of the system (i.e. avoid faltering due to sudden throttle increase when cold.)

The delay valve is supposed to allow the vacuum to equalize to normal air pressure over a period of 9 to 16 seconds, according to the FSM test.

 

You may need to adjust the screw that rests on top of the thermowax plunger.



it's the one I am pointing to there in green. I don't remember if loosening or tightening it will increase cold start air or not. I usually watch TPS voltage as I adjust it with the engine cold or warming up. More TPS voltage means that the throttle plates are opening.