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Removal of Idle Air Control equipment

Whilst driving the car, one of the more annoying 'features' was that I was finding it impossible to get the idle throttle position to stay at what I set it. You could set it perfectly when stationary, go out for a drive and find that when coming up to junctions the engine would stall. If the throttle pedal was moved slowly, it wasn't that much of a problem, but if it was blipped, it was a lot more noticeable.

After lots of experimentation, I noticed that when blipping the throttle, the tubing for the idle air system between the manifolds and the idle air control valve was compressing. When the throttle was closed after the 'blip', the tubing was reverting to its normal dimensions. With such a small amount of air entering the inlet system, it was effectively starving the engine of air, causing it to stall.

The obvious solution was to remove the idle air control valve and associated pipe work. This would have left the inlets, between the manifold and butterflies, open to the world, so they needed blocking. I temporarily blocked these using short M8 bolts in some fuel hose.

Removed Idle Air Control Equipment
Removed Idle Air Control Equipment

Since removing the idle air control equipment, prior to replacing the engine, I covered around 150 miles without any more problems. The engine no longer seems to want to stall when coming up to junctions and the idle stays perfectly set.

The only downside of removing the idle air control equipment is that now, when starting from cold, you have to hold the engine at around 1500 rpm for 30 seconds or so until there is enough heat within the engine for it to idle on its own.

The temporary bolts between the idle air control inlets caused a whistling noise at high RPM so they have been replaced with short lengths of braided fuel hose connecting the two inlets on each throttle body together. This shouldn't cause any balance issues, but if it does, I will insert a block into the middle of each tube to seal them off completely.

Throttle Bodies Showing Braided Tubing
Throttle Bodies Showing Braided Tubing


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