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Hi, I just bought my first diesel car and is an alfa 156 1.9 JTD 16v MJET 140bhp @ 53000 miles.

I find the car idles constantly @900rpm. It is irritating to feel the vibration on the steering wheel and the interior.

There is no power lag or falt spots and pulls like a train throughout the entire range. Therefore I assume the MAF is ok.

But is it normal to have 900rpm in idling?


I have heard stories that some manage to bring the idling rpm to 900 artificially by some strange wire connection procedures. But I dont know the exact way to find if the previous owner has done something like this.

If not what are the things should I be checking for?
Any similar experiences will be greatly appreciated.

Cheers
 

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I'd say that is normal. Because mixtures are very weak these days (even diesels) the idle speed is set a little higher than it used to be.
 

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So is it possible to reset the Idle speed manually? if so anybody has idea on how to set this?

I have done this in my motorbike by just turning a fuel jet screw? sorry for my ignorance,..if this is not the case in cars..
 

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The idle speed is ECU controlled. I don't think there is any adjustment on the throttle body on your car. You possibly need someone with more experience of your car's setup than me.
 

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Idle speed is controlled by the ECU.. But I don't think it should be 900rpm. My 10v JTD idled closer to 600/700..
 

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The idle speed is in limits, but it may just be an over reading rev counter. Reset the ECU and see if it drops.
 
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My 04 plate Sportwagon idles at around 900 as well, same engine with 40k on the clock. I noticed that there's a white segment on the rev counter between 0 and about 650, should the engine be idling at the top end of this segment?

:confused:
 
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I'm sure mine is 900rpm too. If you're suggesting it might possibly be less, surely any vibration would probably be increased?

I've just gone from a twinny to a diesel for the 1st time ever and apart from the lack of smoothness at lower revs and when cold, I am lapping up the wave of torque, the overtaking possibilities I never had before and the 40% improved fuel consumption.

Just one more thing - get a remap! :thumbs: :D
 

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Seems maybe the 16v idles higher than the 10v. Maybe its a smoothness thing?
 
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Possibly I suppose? Could the higher idling speed be in any way linked to the engine temperature? Reading a few other posts on here it seems my thermostat may need replacing, as my temperature gauge constantly reads 70 once warmed up, only increasing if I'm stuck in traffic.

Is it possible that the ECU thinks the engine is cooler than it actually is and increases the mixture/idle to compensate for this?
 

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if i recall correctly my 1.9 JTD 16v idles about there.

Possibly I suppose? Could the higher idling speed be in any way linked to the engine temperature? Reading a few other posts on here it seems my thermostat may need replacing, as my temperature gauge constantly reads 70 once warmed up, only increasing if I'm stuck in traffic.

Is it possible that the ECU thinks the engine is cooler than it actually is and increases the mixture/idle to compensate for this?
yes thats exactly what happens, the ECU actively seeks to heat up the engine.

i changed the thermostat in my car the other week, it runs better, gets up to temperature properly and stays just under 90C. and better still my average fuel consumption has gone from 38-40 to just over 50 doing the same type of driving.
 
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Have to say that I'm not overly concerned by the idle speed, as it sounds like a lot of owners on here are all reporting around 900rpm.

The effect replacing your thermostat has had on your fuel consumption sounds encouraging though. With a mixture of town/A road driving and 20 miles on congested motorway each week, I get around 44mpg. Best I've had is around 47mpg on a longer run.

Are you calculating your figures after filling-up or by using the infocentre information?
 

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Discussion Starter #13
It looks from the above responses that 900rpm is not uncommon. but personally I do not like the car idling and vibrating the interior while in traffic. I am going to do a ECU reset and see if this might change things. I am also thinking of putting a redex disel injector cleaner in addition.
btw, I did a motorway driving Leeds to nottingham mostly on 6th gear and 80mph and to my astonishment the Trip B average showed 59.9 mpg. the urban driving shows 40 mpg. Sweet but unbeleivable...

can anyone tell me if this is practically possible or if something might be wrong with the computer?
 
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if i recall correctly my 1.9 JTD 16v idles about there.



yes thats exactly what happens, the ECU actively seeks to heat up the engine.

i changed the thermostat in my car the other week, it runs better, gets up to temperature properly and stays just under 90C. and better still my average fuel consumption has gone from 38-40 to just over 50 doing the same type of driving.
I'm in the same boat, I think I need to get a new 'stat.

Where's a good place to buy a genuine one cheaply?
 
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The computer is not to be trusted Stealth! Mine shows a consistent average of 47mpg on TripA and after a long run TripB is usually showing an average in the region of 52mpg. I monitor what I'm actually getting by calculating it on the basis of the unused fuel whenever I fill the tank, and this is usually around 44mpg.
 

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*snip*

Are you calculating your figures after filling-up or by using the infocentre information?
The computer is not to be trusted Stealth! Mine shows a consistent average of 47mpg on TripA and after a long run TripB is usually showing an average in the region of 52mpg. I monitor what I'm actually getting by calculating it on the basis of the unused fuel whenever I fill the tank, and this is usually around 44mpg.
i've gone on the info centre from that readings for the before and after new stat. even if the figures are not to be trusted it works out the figures the same way. so it shows an improvement regardless of accuracy or trust.

I got my stat from Shop4Parts came quite quickly and the work was relatively easy, only taking an hour or so.
 
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Thanks Buzz. I'll be interested to see the results once I do mine. Is it a straightforward enough job for someone with only a little experience under the bonnet to tackle?
 

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Well I didnt find it too bad, more time consuming. on my car I had to remove the engine cover and the battery itself (though I didnt remove the battery tray like elearn says to do).
Then remove the pipes and then when they are off there are just two bolts holding the stat on.

Then its just a case of putting it back together in reverse order and refilling the coolant. I took the opportunity to replace the coolant and draining the whole system from the bottom radiator pipe.

Also the coolant will have to be collected and disposed of correctly.
you'll also need new clips most likely, I had to break all the ones on there to get them off and used jubilee clips when i put it all back together.
 
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Thanks Buzz, the new stat arrived today from Shop4Parts, now all I need is for it to stop raining so I can fit it!! One last question for you, I may decide to drain and refill the whole system as you did. On the basis that I'm going to replace the red antifreeze currently in the system with exactly the same, do I actually need to flush it through with a hose?

Cheers
 

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I didn't flush it through, I dont know if that is something that should be done or not. I just drained out as much as possible and then refilled it with the same stuff.

Cant really see why it'd need flushing imo
 
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