If the flap doesn't move the pump won't receive power. This is a saftey feature. If the engine isn't running (ie you're in an accident, you don't want the pump to continue to run.) Cracking the flap allows the pump to run so the car will start. Idle will be poor as the air fuel ratio will be out. O2 sensor can't correct this as it is a fine tuning device trying to correct a bigger problem (only operates at operating temp about 600 degrees). If you let the flap fall back to close, the pump will stop and the engine will quit. If you open the throttle more air is introduced, the system leans out and the engine stalls. Now the thing is to find the leak.
One system is the emissions hoses. These are the hoses going to/coming from cannisters etc.. Some of these hoses have resrictors (plastic pieces narrowing the opening). These hoses must be in correct location and in good shape. If you haven't replaced these hoses I would. You can get bulk hose from auto parts store, it's not expensive. Old hoses can look good but still have micro cracks/leaks. I've included a picture from OEM manual for emissions.
Hose comes from valve cover to flame arrester. Hose from flame arrestor (by valve cover) goes to pipe parrallel to heater pipes. Front of this pipe to top cannister (middle cannister spigot). Rear of pipe to spigot on throttle body.
RH spigot of top cannister to hard pipe to rear (fuel separator by gas tank). At rear, pipe (from front cannnister) to fuel separator, from fuel separator to gas tank. Gas tank cap is sealed to keep this vacuum. If you use a UK cap or locking cap made in UK you are leaking air into intake system.
LH top cannister spigot is blocked off. Bottom of top cannister spigot to top of lower cannister. Bottom spigot of lower cannister to air (goes through positioning bracket).
There is a hose from center large air hose piece to cold air valve then from air valve to air plenum. The air valve is slightly tapered. I had trouble with the hose sliding off as I tightened the clamp so I put some striations perpendicular to it with a file so the hose had something rough to grab onto. I inadvertently left this hose off one end once and engine wouldn't start (leaking air problem).
Make sure the rubber hoses fit snuggly on their metal connectors. and well clamped. Large air hose (two pieces) is rubberized fabric and can leak. I reinforced mine with black duct tape. If you replace this with after market hose make sure it is well clamped to metal connectors.
There is a small hose from the front of the air plenum to the fuel regulator and if not good, can be a source of a leak.
There is a hose from air plenum to brake booster to supply vacuum to brakes. There is a one way valve in this line somewhere, some diagrams show it in the middle but on FI it's either at one end or the other, not sure which.
Incorrect hose placement , leaking hoses, poorly clamped hoses will leak air into vacuum preventing car from running/starting properly. Just because a hose looks good doesn't mean it isn't leaking. If I don't know the history of a hose I replace it.
This setup is unique to FI models. Carb people have their own leaking problems with the result usually of a high idle speed that can't be brought down.
TR7 Spider - 1978 Spitfire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT
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