backfire ??

Braincrank

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I wonder if anyone could point me in the right direction as to where to start ...
For quite some time now I notice that when I drive on the motorway and I take my foot of the gas then from 2.5k to 2k rpm the engine dose a ticking noise that sounds like a little backfire ...
As soon as the refs get below 2000 it stops .
Any idea what that might be ?
200E, auto, 124
 
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Braincrank

Braincrank

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I'm still at a loss .....
anyone out there who might have a clue ?


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190

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Not sure if this helps. If we are talking about Bosch Ke fuel injection then it should have fuel cut off on the overrun above a certain engine speed which I would have thought precludes backfires. When the revs fall below a defined point the fuel kicks back in again. This transition was just about perceptible on my 190e although I think it was at less than 2000 RPM. I'm wondering if your fuel cut off is not working as it should.
 
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Braincrank

Braincrank

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Hm, thanks for your reply.
It only started doing it about 10 months ago ...
The car runs and idles fine and i have not problems with it .


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alabbasi

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Does it happen only when warmed up or also when cold? When coils fail (usually when hot) they'll start falling on their face under load.
 

grober

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This only applies the car has the single cam M102 ENGINE

http://www.berlinasportivo.com/Technical/lancia/Thema832/Bosch-KE-Jetronic-OCR.pdf

page 23 describes fuel cutoff on the overrun.

A backfire refers to fuel igniting where it shouldn't not in the cylinder but in the inlet or exhaust. I suspect that the overrun cutoff may not working properly allowing unburnt fuel into the hot exhaust where its igniting. This could be caused by several things throttle position switch and possibly more likely the electro-hydraulic pressure actuator
 
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Braincrank

Braincrank

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Joined
Sep 12, 2012
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371
Location
West London
Car
Mercedes 200E
I don't even know if it is a backfire ....
It's a sort of ticking noise .
I revved the engine to 3k rpm at standstill and when I took the foot off the pedal I could hear is for a second . It lasts much longer when driving because the car takes longer to slow down and the revs go down slower .


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