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Discussion Starter #1
Hello All,
I've owned a couple of Alfas but this is the first with a 2 litre JTS engine. There is definitely a problem with it. It has a distinct erratic idle when cold and once warmed up a whining sound at low revs from the engine.
Symptoms:
1. Takes a few goes to start - once started idles around 1000 revs but if you slightly increase revs to 1500 or so it is erratic, dies back to 1000 then back up etc . So you need to rev it to safely move without it stalling. It seems to operate normally at higher revs.
2. But once warmed up you can hear a whine sound coming from the engine bay - this only occurs at low revs it disappears once you rev it.
So under bonnet:
I initially thought the sound originated from around breathe pipe between rocker cover to pcv valve and inlet manifold. First thing I noticed was when you squeeze breather pipe the whine sound went away. Thinking possibly blocked pcv valve I have removed and cleaned pcv valve but still occurring. I've also removed breather pipe and checked both ends.
On closer observation I'm now thinking the whining sound is originating from engine as though it is sucking air maybe. Removed oil dipstick and whining sound went away.
Does this make sense to anyone? I have read various threads but none necessarily have these symptoms.
Any help would be greatly appreciated.
Cheers, David
 

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Sounds like a vacuum leak, have you checked for splits or cracks in all of the air hoses? A quick pointer on where to look would be to start the engine and spray deodorant (or any flammable spray really) at the hoses one by one. If the revs raise you've got a leak, so check in the area you sprayed that raised the revs.
Not too sure about the 2.0 jts as mine is the the gm 2.2 but there may be hoses under the inlet manifold that could be the culprit as on my engine.
 

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Discussion Starter #3
Thanks, - will recheck all hoses. Car at mechanics so will mention vacuum test and check around inlet manifold. I think the 2 litre is slightly different than 2.2 but will check out inlet manifold.
Will update once visited workshop. Cheers, David
 

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Vacuum leak. Throttle body not calibrated properly since battery either disconnected or replaced is a possibility for poor running. Dirty throttle body as well can contribute to poor running especially at idle.

Not sure about the whine. You could post a video if you can of it making that noise for people to offer more useful advice on.
 

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Discussion Starter #5
Thanks for the replies.
Further to the erratic idle and whining sound - update:
1. Cleaned and tested pcv valve.
2. Tested for vacuum leaks around hoses, joins and inlet manifold. tested for blockages in hoses.
3. Done throttle reset.
Here is a video of the sound from engine when idling after warming engine. (Note the sound is not there when engine cold although idle is erratic at low revs)
My mechanic is opening and closing oil dipstick hole thus releasing crankcase pressure as affected by the manifold vacuum - and you can hear sucking noise coming and going.

After closer examination on hoist my mechanic is sure it is sucking in through the rear crank seal.
Can anyone help explain why this would be happening. Blockage? I've searched many posts and this has never been mentioned.
Great to hear from anyone with any ideas and possible fix.
Cheers, David
 

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How clean are the inlet valves? Direct injection engines can suffer from carbon build-up on the valves and inlet ports which can cause all sorts of running issues such as erratic idle and flat spots throughout the rev range.
It's simple enough to check, just pull the manifold off and look down the ports. Cleaning is fiddly and time consuming - oven cleaner works wonders! - but an easy job and you shouldn't need the head removed unless it's totally gummed up!
 

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Discussion Starter #7
Thanks for these suggestions -
With regards to throttle body we will need to look at this. We haven't concentrated on the air flow side before the throttle body - so will look at inside of the throttle body for cleaning. And do a throttle reset.
I will follow up the state of the inlet valves once the workshop is open. Since recently acquiring the car we have done a timing belt change and noticed a worn lobe on the inlet camshaft so that has been replaced. Whether the inlet valves were checked - will find out and report back.
I did notice in searching on the forum regarding inlet valves that the Spider jts engine is slightly different to the 156 in some respects. So I have posted on the Spider section of the forum in case there is something specific in that regard.
Having never owned a car with a JTS engine before I'm sure they perform really well - so am looking forward to getting to the bottom of this.
Regards, David
 

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This may be of some use;
This is not something I've come across so I'll not pretend to know what is causing the noise. My experience only showed the carboned noise appearing at high engine speeds with larger throttle openings. How a worn camshaft may affect things is a complete unknown but it may be possible to have an indication if short term fuel trims are vastly different between slow speed running and high speed running with throttle. I've never really looked at that but it is an idea.

My guess is that giving the engine a momentary full throttle acceleration from idle speed would change the direction of the crankcase ventilation. John Lear explained very comprehensively in a post how the PCV system works. There is suction at idle and low throttle and piston blow-by at large throttle openings. If large throttle openings eliminate the noise, that may provide a clue as to where to look next.
 

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Discussion Starter #10
Fruity thanks for your input - so from what you have experienced inlet valves that have high carbon have exhibited noise at high revs not low, which is what is happening in our case. Although carboned inlet valves can effect idle which is happening in our case. From my reading Spider 2003 has a slightly modified system which you mentioned in the other post. It will be interesting discussing this with my mechanic tomorrow - hopefully he knows the state of the inlet valves. I have provided with him John Lears information about crankcase ventilation. I am sure our pcv valve is operating properly but would be good idea to readdress tests highlighted in his post.The extent of blow back at higher revs. Also assess throttle body condition. I'm sure we are getting close to solving this. I will look at Multiecuscan tomorrow - I'm sure there is a throttle reset option also.
 
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