1.9 JTD 16V RPM drop when stopping - Alfa Romeo Forum
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(Post Link) post #1 of 15 Old 10-12-13 Thread Starter
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1.9 JTD 16V RPM drop when stopping

Hello Guys,

Hope you can help me on a very annoying problem that I experience with my '08 AR 147 Q2 1.9 JTD 16V (150 hp model).

The problem is that whenever I'm driving, disengage gear and come to complete stop the rpm of car drop below normal idle point for a second and then normalize to regular idle.
Problem doesn't always happen but let's say 2 of 5 stops rpm will drop when stopping and in neutral then idles normally?!

Can brake or clutch switch be somehow connected?
My other assumption is - MAF or vacuum?

Any help on the topic will be appreciated.

Last edited by radoslavp; 10-12-13 at 18:48.
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could be wrong but got a feeling on idle there are no sensors involved other those measuring rpm ,crank,cam sensors maybe, just tries to keep desired rpm and increases or decreases fuel injected quantity to maintain rpm.
the maf im not sure would affect as its probably running around plus 100:1 afr at idle at around 5mm3 for around 500mg/I of maf air so well above the smoke limiter maf might affect.
unplug maf and test?
do you still have egr operational? a quick blank to check if improvement.
both will throw up codes and eml during test.
vacuum ? you thinking throttle anti shudder flap partially closing ?
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Quote:
Originally Posted by sussexa View Post
could be wrong but got a feeling on idle there are no sensors involved other those measuring rpm ,crank,cam sensors maybe, just tries to keep desired rpm and increases or decreases fuel injected quantity to maintain rpm.
the maf im not sure would affect as its probably running around plus 100:1 afr at idle at around 5mm3 for around 500mg/I of maf air so well above the smoke limiter maf might affect.
unplug maf and test?
do you still have egr operational? a quick blank to check if improvement.
both will throw up codes and eml during test.
vacuum ? you thinking throttle anti shudder flap partially closing ?
Vacuum ... exactly, I have EGR completely disabled (both hardware/software) and shudder flap removed.
I'm thinking could it be from it being removed? I had it removed on my 8v engine before and it didn't have such effect at all.

Can I have the crank and cam sensors measured in some way, multiecuscan?
Haven't got any problems with car shutting down while hot till now (possible crank sensor fault).
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If you have multiscan , try logging rpm and total fuel injection, maybe injector correction values, and drive to recreate bog down in revs, maybe a big carpark would be handy.
Also a log of rail pressure and desired fuel pressure and regulator and rpm maybe.
With egr out of picture, and inlet flap also gone vacuum is only left going to brake servo and vnt on turbo.
I recently did test on completely removing vac to turbo vnt and refitting and dont remember it affecting rpm at all.
Are map and maf sensor readings looking normal or believable anyway.
Last thought does it have swirl flaps? Functioning ok?
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clutch sensor does have a bearing, there's different idle strategies for different kinds of idle.

there's running idle and stationary idle for example.

does it happen regardless of engine temperature?
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Quote:
Originally Posted by Cuore_Sportivo_155 View Post
clutch sensor does have a bearing, there's different idle strategies for different kinds of idle.

there's running idle and stationary idle for example.

does it happen regardless of engine temperature?
Where is the clutch sensor situated?

It happens more when the engine is up to temperature and less when cold.
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the clutch switch is fitted to the clutch pedal. put you head where your feet normally are.
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Quote:
Originally Posted by Cuore_Sportivo_155 View Post
the clutch switch is fitted to the clutch pedal. put you head where your feet normally are.
Help me out more, does this mean that the clutch switch could be faulty? Can I somehow test that?
Will changing it cure the problem?
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do you have cruise control, and is it working properly? if so, the switch will be working properly
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Cuore_Sportivo_155 you are my man, thanks a lot for the help.

I recently did full flywheel/clutch change and as mandatory step for this procedure there was some manual clutch pedal pumping until the system is filled up with oil and operational (this could of screwed the clutch switch default position).

Although my cruise control worked fine, I unplugged the clutch switch today pulled the pin and resitted again by carefully releasing the clutch pedal.

After that I drove for a whole day, and hey ... no sign of the problem!

Hope that really did the job, still hard to imagine how this simple on/off switch can be such a pain.

Thanks once again for your help, much appreciated.
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I don't know if I understand your problem properly but it sounds like the egr valve?
 
(Post Link) post #12 of 15 Old 21-12-13 Thread Starter
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Quote:
Originally Posted by rhett71 View Post
I don't know if I understand your problem properly but it sounds like the egr valve?
EGR is software and hardware disabled as I pointed in above posts.

EGR common problems are loss of power, judder, a lot of black smoke.

My problem was that car drives perfectly fine, but when rolling and you get to stop (traffic light for example) exactly when stopping the rpm would drop to around 800 for a split second and than come back to ~852 rpm normal idle. This was particularly nasty as you can feel the engine is trying to die every time you get to a neutral and stop, than resumes normal operation.
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Hope its sorted,
Not seen before on here, must be a rare one, but one to remember.
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sorry radoslavp never saw the posts pointing that out hope you find out what is wrong and don't forget to fill us all in when you have got it sorted.
 
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ALFA GT 1.9 JTD

Quote:
Originally Posted by radoslavp View Post
Cuore_Sportivo_155 you are my man, thanks a lot for the help.

I recently did full flywheel/clutch change and as mandatory step for this procedure there was some manual clutch pedal pumping until the system is filled up with oil and operational (this could of screwed the clutch switch default position).

Although my cruise control worked fine, I unplugged the clutch switch today pulled the pin and resitted again by carefully releasing the clutch pedal.

After that I drove for a whole day, and hey ... no sign of the problem!

Hope that really did the job, still hard to imagine how this simple on/off switch can be such a pain.

Thanks once again for your help, much appreciated.
i have the same problem.What exactly i must do to fix it ?
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