Rover 3500 V8 EFI Flapper high revs on cold start

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davejclear@hotmail.com
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Rover 3500 V8 EFI Flapper high revs on cold start

Post by davejclear@hotmail.com »

Hi

Never been on here before so be gentle with me!

I have recently purchased an MGB Roadster V8 conversion, almost complete project. The engine is a rover V8 3500 EFI flapper but has had new liners and 3.9 pistons and upgraded heads timing chain etc.

When I got the car it was massively over fuelling so I checked every component, connection and parameter. I got the injectors overhauls, and finally sent the ECU away for testing and repair finally sorting out the over fuelling.

Now it starts just fine with no black smoke, Battery and alt packed up so changed these. However, now it starts but revs up to 3000 RPM for about 5 mins and then slowly drops to 1500 and then down to 1000 and final stalls. This feels like the 'extra air value' and ECU are doing their cold start jobs but the engine over reving is the concern.

Any ideas?



DaveEFI
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Post by DaveEFI »

The fast idle (extra air valve) on the flapper is entirely independent of the ECU. It is basically a heat operated valve which closes down as the engine heats up. It has an electric 'accelerator' coil to improve the response when near cold.

You can check its effect by crushing the rubber hose from it to stop any flow.

I've no real guess why or how it could allow the engine to rev so high - is it the correct part?

A high idle speed is usually down to an air leak somewhere.

The only mixture control on the flapper is a bypass on the flapper itself which only sets the idle mixture. Again, that doesn't do anything to the ECU itself.

The actual throttle disc should be set so it is only just cracking off being totally closed at idle - you use an 0.1mm (0.004") feeler gauge to set this. The idle then being set by the throttle valve bypass circuit and idle speed screw on the top of the plenum.
Dave
London SW
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