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Backfiring during shifts

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I have recently noticed a "pop", or a backfiring sound during gear changes. It's after the gear is selected, right when the accelerator is pushed. Even if I'm in 5th, let off the accelerator and then press it again, I get the same pop.

Any ideas?

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it may be the EBPV slamming shut and open as you unload when in the middle of the shift. IT makes a loud pop/bang.

You can try to wire it open and drive around to see if it goes away - at least that will eliminate it.


Lou Senko

Austin, TX

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Un burnt fuel on various degress of acceleration and changing down will give you crackles and pops. If its more of a back fire sound pull the plugs and see what condition they are in (black, white, grey etc) check gaps too. A good starting point anyway. :)


350.gifNo.23

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the EBPV is held open with vacuum - so the vacuum can unload with quick dips in engine load.

I backfire when I come off a heavy runs then downshift and let the car runs down on load - I have no CAT and no muffler... so it spits and sputters while coasting down from high-level.


Lou Senko

Austin, TX

more, more, more....

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Un burnt fuel on various degress of acceleration and changing down will give you crackles and pops. If its more of a back fire sound pull the plugs and see what condition they are in (black, white, grey etc) check gaps too. A good starting point anyway. :)

Plugs have a little oil on them....it is thought that this is from the valve cover gaskets leaking as there is oil in the plug wells.

the EBPV is held open with vacuum - so the vacuum can unload with quick dips in engine load.

I backfire when I come off a heavy runs then downshift and let the car runs down on load - I have no CAT and no muffler... so it spits and sputters while coasting down from high-level.

I have a gutless cat. It just recently started doing this.

How should the plugs look?

Would too little or too much gap cause this (which one)?

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I have no CAT and no muffler... so it spits and sputters while coasting down from high-level.

I bet that sounds just AWESOME! ^_^

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I just got my new camera mount - suction cup to tie the video camera to the rear window - soooo hopefully I'll be able to capture both the video and audio next time I'm on track - the noise is certainly part of the experience.... ^_^


Lou Senko

Austin, TX

more, more, more....

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I have a gutless cat.

If you mean your cat is empty of anything, then popping and banging when lifting the throttle is perfectly normal.

If you nail the hot engine hard in 3rd or 4th gear then lift and then re-apply gently, you've got a good chance of producing flames out of the exhaust. This, by the way, is a good thing.

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My old S4s always did this ...


Paddle Faster, I hear Banjos!

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If you mean your cat is empty of anything, then popping and banging when lifting the throttle is perfectly normal.

If you nail the hot engine hard in 3rd or 4th gear then lift and then re-apply gently, you've got a good chance of producing flames out of the exhaust. This, by the way, is a good thing.

Why is it a good thing?

I should have stated before that it only happens when the engine is hot (80+).

Thanks for all the info, guys!!!!!

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Ive been told I have lots of flames and 'explosions' out of mine....

Yep its de-cat etc etc

I love it!

^_^


Gavman

Lotus Esprit Turbo Chargecooler SE 1991

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popping and banging could be an early indication of an exhuast manifold on its way out! Its also a symptom if the cam timing/ignition timing is slightly out.Sorry so the doom and gloom!

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If you mean your cat is empty of anything, then popping and banging when lifting the throttle is perfectly normal.

If you nail the hot engine hard in 3rd or 4th gear then lift and then re-apply gently, you've got a good chance of producing flames out of the exhaust. This, by the way, is a good thing.

Good answer. I like that. Not sure why it's good but I'll go along with the notion. :cheers: Cheers.

popping and banging could be an early indication of an exhuast manifold on its way out! Its also a symptom if the cam timing/ignition timing is slightly out.Sorry so the doom and gloom!

Dammit, Chris :flower: , that's not what I want to hear....but thanks for the info. I'll have to keep an eye on it.

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What is it like on the MOT without a cat? I know the older ones before 1993 (i think) don't have to have one, but does it get through ok.

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What is it like on the MOT without a cat? I know the older ones before 1993 (i think) don't have to have one, but does it get through ok.

I failed inspection by a VERY narrow margin until I had an inline Cat (temporarily) installed. Keep in mind this car sat for 3 years before I rescued it. I believe Quikr passed his inspection by a narrow margin.

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Mine's an '89 (I think the rules are post '91 need a cat) and it passed easily, in fact with lower emissions that Laura's CoF (Corsa of Fury)

I've not cat nor silencers and it sound like a thunderstorm is chasing me down the road. It can backfire between shifts with a healthy flame and also backfires a lot on zero throttle (or partial, little taps) overrun! I like it!


88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

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