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Unusual behaviour when I put the clutch down

Hello,
When I push the clutch down to change gear the revs stay at where they were before I put the clutch down for about a second or two before they drop again and this is with my foot off the accelerator. They stay at 2,000 rpm with the clutch down for a second. If I rev to 2,500 before putting the clutch down, this problem doesn’t happen and the revs drop. It only seems to happen when the engine is at 2,000 rpm and no other rpm. It’s an unusual one. It isn’t much of a problem as it doesn’t really effect me but I’m curious it’s the starting symptom of a problem down the line. I am thinking it could be a dirty butterfly valve in the throttle body which sticks more at this particular rpm, 2,000 rpm or a clutch plate thst isn’t releasing properly but I don’t believe the latter is the case if it doesn’t do it at other rpms.

2006 1.3 Petrol Suzuki Swift.

Thank you

I suggest that you clean the throttle body. If that doesn’t help then it is possible that the throttle position sensor is wonky. Is the Check Engine Light on?

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There is no check engine light and no fault codes. If I Rev the engine to 2,000 rpm in neutral the revs drop straight away it’s only when the clutch is pushed down while driving to change gear

Is this something new, or maybe something you never noticed before?

I have the car second hand so it may be something I haven’t noticed before and just shifted gears without noticing it

Cars sometimes do strange things like that as a way to control emissions. When you shift gears there’s a moment when you suddenly take your foot off the gas and that can create a sharp vacuum and a rich mixture that doesn’t burn right. So keeping the revs up by having the throttle plate stay stay open would let the gas burn more fully?

Maybe.

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Might be a good idea to just worry a little less and if something breaks then fix it . It is an old vehicle so quirks are to be expected. If you are really concerned then paying a shop to look it over for a fee might set your mind at ease. I would just drive on .

Somewhere back in time I recall several cars with manual transmissions which delayed the throttle dropping to full idle and some that raised the idle speed when the clutch was depressed. It was explained to me that a combination of emissions and avoiding momentary engine braking for new manual shift drivers was the purpose. I might try my luck at back tracking the situation.

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Yeah I’m probably worrying about it too much! As i said it doesn’t really seem to affect me and could be an emissions thing. Yeah if something breaks I’ll worry then. Thanks everyone

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My 2002 Miata does that when the engine is cold.

add 1 to Rod-Knox. When a car was coasting, throttle closed, a high vacuum formed above the piston tops and a very high level of pollution came out the tailpipe - maybe nitrous oxides and/or others

Starting some time in the 1970s a vacuum-operated device was added. It would hold the throttle partly open for a few seconds or more, and this pollution was reduced.