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Old 13-09-2007   #1
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Question Desired Idle revs, rough idle, slack throttle cable?

Does anyone know the min-max desirable idle revs speed for an mpi sei?

I have no idea how many revs mine does on idle because the needle just sits below 800 (starting position), and doesn't move until I open the throttle.

The reason I ask is that she is rather rough (think v8 judder!) on idle - yet the moment you blip the throttle she calms down.

If I nudge the accelerator slightly and take the revs up to just over 800 (very fractional movement - no noticable increase in engine noise), she's calm as anything, and behaves herself very well.

Wondering if I should adjust the cable slack on the butterfly (and also if there is an easy way to DIY this - on my old cinq you could take up a little bit of slack wth a screw adjust, like the brakes on a mountain bike).


EDIT: Sorry - should probably mention that she's a 2001 abarth with 27k on the clock, new hg recently and all other "rough idle suspects" ie plugs, leads, filter, oil, rad etc have either been checked or replaced in the last two weeks, and ecu reset since to re-train itself.
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Old 13-09-2007   #2
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Re: Desired Idle revs, rough idle, slack throttle cable?

Ronnie, you are too paranoid, it all sounds ok to mine used to idle like this all the way throughout my ownership
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Old 14-09-2007   #3
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Re: Desired Idle revs, rough idle, slack throttle cable?

Quote Originally Posted by AppleSei View Post
Ronnie, you are too paranoid, it all sounds ok to mine used to idle like this all the way throughout my ownership
lol - it's not so much paranoia, I know that there's nothing wrong with the way she idles - I just don't want her to idle like that, feels like I'm sat behind the wheel of a bloody mustang!
Had this very same problem with the cinq after I'd fettled him up, but a small adjustment on the throttle cable and an ecu reset cured him... just wondering if it's possible to do something similar by taking up a little more slack on the butterfly?
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Old 14-09-2007   #4
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Re: Desired Idle revs, rough idle, slack throttle cable?

about 850 is right....engine rocks a bit and smooths out when a bit more throttle applied.

100% normal , its all to do with emissions, as long as it doesn't hesitate when you accelerate or cut out, you have nothing to worry about!

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Old 14-09-2007   #5
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Re: Desired Idle revs, rough idle, slack throttle cable?

Quote Originally Posted by kritip View Post
about 850 is right....engine rocks a bit and smooths out when a bit more throttle applied.

100% normal , its all to do with emissions, as long as it doesn't hesitate when you accelerate or cut out, you have nothing to worry about!

Cheers,

Kristian
no hesitation, never threatens to cut out...

So lets say for example I did take the throttle cable in a wee touch - just a tiny adjustment.
Any detrimental side effects? - I'm assuming the idle test on MOT would possibly be one area of concern, but never had any issues with that from the cinq (although he was a much older car so obviously emissions test not as strict).
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Old 14-09-2007   #6
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Re: Desired Idle revs, rough idle, slack throttle cable?

There is a small screw to crack the butterfly open a bit, would be a better solution than adjusting the cable. That will just lift the pedal higher in the air quite a bit before it makes a change.

I would imagine the IAC stepper would constantly be fighting though, to try and drop the revs, so may not be good for it. Not sure about MOT and emissions. If it fails, put it back to normal and retest.

tbh I wouldn't bother though

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Old 14-09-2007   #7
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Re: Desired Idle revs, rough idle, slack throttle cable?

Quote Originally Posted by kritip View Post
There is a small screw to crack the butterfly open a bit, would be a better solution than adjusting the cable. That will just lift the pedal higher in the air quite a bit before it makes a change.

I would imagine the IAC stepper would constantly be fighting though, to try and drop the revs, so may not be good for it. Not sure about MOT and emissions. If it fails, put it back to normal and retest.

tbh I wouldn't bother though

Kristian
Will play around with it and see what happens
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Old 14-09-2007   #8
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Re: Desired Idle revs, rough idle, slack throttle cable?

I'd leave that screw well alone. The idle is controlled by a valve called the err.... Idle control valve but if you open the throttle (as thats what you do if you adjust the screw) then i guess the ICV will have a hard time keeping revs down.

I would do as you suggested, take out any slack in the cable. Easy to do, will take about 2 minutes. And easy to put back.

But, personally, it sounds like your car is fine as it is, cars idle is not set 100%, so it can go up or down slightly, and at those low RPM's there can be silght vibrations at certain engine speeds. Nothing wrong at all.
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Old 14-09-2007   #9
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Re: Desired Idle revs, rough idle, slack throttle cable?

Quote Originally Posted by balidey View Post
I'd leave that screw well alone. The idle is controlled by a valve called the err.... Idle control valve but if you open the throttle (as thats what you do if you adjust the screw) then i guess the ICV will have a hard time keeping revs down.

I would do as you suggested, take out any slack in the cable. Easy to do, will take about 2 minutes. And easy to put back.

But, personally, it sounds like your car is fine as it is, cars idle is not set 100%, so it can go up or down slightly, and at those low RPM's there can be silght vibrations at certain engine speeds. Nothing wrong at all.
No ICV on my engine - idle speed is controlled by a stepper motor connected to the butterfly.

I know there's nothing wrong with the way she's running - just isn't right for me, don't like feeling like I'm driving a diesel every time I have to stop at traffic lights
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Old 14-09-2007   #10
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Re: Desired Idle revs, rough idle, slack throttle cable?

Quote Originally Posted by ronnieronson View Post
No ICV on my engine - idle speed is controlled by a stepper motor connected to the butterfly.
Well, every days a school day. I didn't know they had that
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Old 14-09-2007   #11
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Re: Desired Idle revs, rough idle, slack throttle cable?

Quote Originally Posted by balidey View Post
Well, every days a school day. I didn't know they had that
more common on the mpi's I believe...

In theory adjusting the throttle cable shouldn't upset the idle stepper too much (so long as the adjustment is kept sensible), but obviously take up too much cable and the throttle will stay too open on idle, which leads to all sorts of issues - the main one being idle emissions test on MOT, not to mention the all important fuel economy.

I'm thinking I need to spend a day stripping out the garbage in the engine bay and investigating - need to check the stop cock on my internal heater assembly as well, so I suppose Ile be killing two birds with one stone so to speak.
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Old 14-09-2007   #12
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Re: Desired Idle revs, rough idle, slack throttle cable?

Quote Originally Posted by ronnieronson View Post
I know there's nothing wrong with the way she's running - just isn't right for me, don't like feeling like I'm driving a diesel every time I have to stop at traffic lights
If a tiny thing that is perfectly normal 'isnt right' for you, you are never going to get on with this car and enjoy owning it.

Poking around may make it worse also

IMO i think you havent got used to the cinq/sei spi/mpi thing yet and are imagining things what happened to Bertie are going to occur here
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Old 14-09-2007   #13
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Re: Desired Idle revs, rough idle, slack throttle cable?

Quote Originally Posted by AppleSei View Post
If a tiny thing that is perfectly normal 'isnt right' for you, you are never going to get on with this car and enjoy owning it.

Poking around may make it worse also

IMO i think you havent got used to the cinq/sei spi/mpi thing yet and are imagining things what happened to Bertie are going to occur here
Lol.... you could have a point there mate... what can I say - I'm paranoid
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Old 15-09-2007   #14
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Re: Desired Idle revs, rough idle, slack throttle cable?

the little judder is perfectly normal an on the mpi, as every one has said. but i must admit i thought there was something wrong aswell but i just got used to it and now i just dont think about it. its just part of the sei's personality that makes it what it is
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