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V8 Flat Spot


bloomers
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3.5 V8 efi Flapper...

Bad Flat Spot/ Miss ? when hot...

Had a problem with the ignition Amp, so fitted a new one, now its developed a bad flat spot when accelerating from idle only when the engine gets warm/hot, from cold you wouldn't think there's a problem...

Tried a different...

Coil

Distributor Cap

Plugs

Leads

Distributor pick up point (inside the Distributor)

So I'm now pointing towards the fuel pump, maybe thats playing up when it gets hot, but that has nothing to do with the original problem...

I keep going round in circles...

Any ideas would be appreciated...

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3.5 V8 efi Flapper...

Bad Flat Spot/ Miss ? when hot...

Had a problem with the ignition Amp, so fitted a new one, now its developed a bad flat spot when accelerating from idle only when the engine gets warm/hot, from cold you wouldn't think there's a problem...

Tried a different...

Coil

Distributor Cap

Plugs

Leads

Distributor pick up point (inside the Distributor)

So I'm now pointing towards the fuel pump, maybe thats playing up when it gets hot, but that has nothing to do with the original problem...

I keep going round in circles...

Any ideas would be appreciated...

Could be lots of things. The tech section will help, otherwise search using "flapper" and you will find similar questions.

In this case the stock answer is that you have probably got air leaks on one or more of those rubber hoses around the plenum, jubillee clip them all. (they have gone soft over the years and get even softer when warm)

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It would be worth checking the throttle position sensor, they're supposed to provide a clean smooth signal from closed to open but sometimes they get a bit of dirt or a bad track and it causes the engine to hesitate as the ECU thinks you just closed the throttle again. If it's a worn track this can get worse as it heats up although it's unusual to be heat related.

Leaks in air pipes as above are a prime candidate, accelerating hard is the point at which you have the highest vacuum in the plenum chamber and warm pipes are softer so more prone to opening up any cracks/splits in them. They allow air to bypass the flapper and the mixture leans out as a result.

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