159 2.4 Stuttering and boost pulsing - Alfa Romeo Forum
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(Post Link) post #1 of 24 Old 14-10-17 Thread Starter
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Question 159 2.4 Stuttering and boost pulsing

Hi all! Taken me a year to sign up to this forum for some reason but I've had my 159 Ti since last October and I love it!
I do however have a persisent issue that doesn't stop me from driving it at all but does stop me from enjoying it when pushing on.
The car is a 159 Ti 2.4JTDM with an Alfatune remap, EGR delete, DPF delete and swirl flap delete. So should be 260bhp approx.
First of all it doesn't feel that fast, no torque steer or anything of the sort. It's not slow, just not as rapid as the power and torque numbers would indicate. Secondly it is VERY smokey on full throttle. But mostly annoying is the boost pulses when under heavy load. You can hear the turbo spooling then dropping off repeatedly, this is accompanied by a very slight hesitiation each time, all the way through the rev range to the redline. In 4th, 5th or 6th this is sometimes accompanied by a really bad stutter/hesitation at around 2000rpm, and you can see the boost gauge actually dropping down from top to midway and back up again a couple of times.
I've cleaned map and maf sensors, replaced the boost solenoid (for another problem), checked turbo hoses etc
Is this a sign of sticking turbo vanes? Or is there anything else to try before I get the turbo off?
Thanks!
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Any fault codes at all?
I would double check all the vac hoses again, especially the small one coming off the boost solenoid under the engine cover - Give them a squeeze, any soft spots?
Remove boost solenoid and try blowing through it, I know you said it was replaced but worth checking that it’s not faulty?
Throttle unit, is this sticking? Was it removed and cleaned when you deswirled the manifold?
MAF sensor:
Easy to diagnose, tends to show up first above 2,000rpm (across the range when it's fully dead), simply unplug the sensor, and should give 'normal' performance. Sometimes associated with a bit of smoke. You may be able to get away with just giving the sensor a bit of a clean (spray cleaner, avoid touching it). A faulty MAF can be linked to a failed EGR, as it can send the EGR crazy as it tries to compensate.
Also only tends to be an issue when the car is warm, as the engine uses a default map up until it reaches operating temperature.

Alrite-kid

Last edited by Topic; 14-10-17 at 10:15.
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(Post Link) post #3 of 24 Old 14-10-17 Thread Starter
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No change with MAF disconnected
Same issue with 2 different boost sensors/solenoid
Vacuum checked all the lines, all come up ok
Fault is there hot or cold
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Now strangely mine does the same thing, if I plant my foot down in a high gear the car hesitates while accelerating, strangely if I run it through the gears it seems fine. Also as you say the boost gauge fluctuates. I have cleaned everything, the conclusion I have come to is that the turbo is coked up and not allowing the VNT? thingy move properly. Apart from that my love hate relationship with it continues.
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Sounds like it could be boost spiking. Do you have access to fiat multiscan at all? You could monitor the actual boost values and the requested boost values.

Might not be so noticeable during long smooth acceleration as you aren't requesting a sudden boost rise.
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I actually work for a Fiat authorised repairer so need to get one of the techs to give me a run down of how the diag computer works!
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Originally Posted by luk3b3nson View Post
I actually work for a Fiat authorised repairer so need to get one of the techs to give me a run down of how the diag computer works!
Where abouts are you based? Working at a fiat garage should definitely help!! haha
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Ok, I am motivated, I will get my MES on it and see whats what.
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This maybe a knackered turbo which is coked to death which kills the bearing...

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Mine had a similar problem - turned out to be a boost leak.
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Originally Posted by OldSmokey159 View Post
Mine had a similar problem - turned out to be a boost leak.
You mean a split pipe or similar?
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Had a quick play with the Examiner today (before the battery died on it...)
If i?m looking at the correct thing it would appear to be overboosting looking at parameters. target max says 2700mbar, it?s hitting beyond this and then dropping way back down again before coming back up and repeating the process. Only under full throttle.
I believe this is usually an issue with the sticking turbo vanes? Looks like next step is to throw some beers at a technician and get him to take the turbo off
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Quote:
Originally Posted by luk3b3nson View Post
Had a quick play with the Examiner today (before the battery died on it...)
If i?m looking at the correct thing it would appear to be overboosting looking at parameters. target max says 2700mbar, it?s hitting beyond this and then dropping way back down again before coming back up and repeating the process. Only under full throttle.
I believe this is usually an issue with the sticking turbo vanes? Looks like next step is to throw some beers at a technician and get him to take the turbo off
I think thats my reason the problem, I was going to try the oven cleaner route but as yet I have not felt like grovelling under neath the car. I have also noticed that I can hear a slight whine form the turbo so it may be on itís way out, if so a new one will cure the issue.
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Originally Posted by Philjay50 View Post
You mean a split pipe or similar?
Swirl flaps in my case and lower turbo hose.
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Originally Posted by Philjay50 View Post
I think thats my reason the problem, I was going to try the oven cleaner route but as yet I have not felt like grovelling under neath the car. I have also noticed that I can hear a slight whine form the turbo so it may be on itís way out, if so a new one will cure the issue.
Oven cleaner? Thatís a new one on me??
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Oven cleaner? Thatís a new one on me??
Have a hunt around YouTube there are quite a few examples, basically undo the exhaust side and fill the turbo with something like Mr Muscle, leave for a while, occassionaly playing with the vacuum arm to help it free off. Put bact together and off you go, apparently works very well.
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Have a hunt around YouTube there are quite a few examples, basically undo the exhaust side and fill the turbo with something like Mr Muscle, leave for a while, occassionaly playing with the vacuum arm to help it free off. Put bact together and off you go, apparently works very well.
Yeah I believe this originated from the VW Tdi diesel from around 2003 where the vanes were always sticking on them. Seems that oven cleaner dissolves dirt very well and clears the vanes a treat.


HOWEVER.. If I was to do it on one of these cars I would unbolt the DPF at the front and allow the exhaust to blast any crap and cleaner out before re-attaching it.
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Yeah I believe this originated from the VW Tdi diesel from around 2003 where the vanes were always sticking on them. Seems that oven cleaner dissolves dirt very well and clears the vanes a treat.


HOWEVER.. If I was to do it on one of these cars I would unbolt the DPF at the front and allow the exhaust to blast any crap and cleaner out before re-attaching it.
Just debating if this is a good idea?
Does it have no catastrophic effect on the seals or bearings??
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Oven cleaner works well, have uesd it on a vw�� with a vacumepump. Vanes vere just about solid and got them to full range after some hours, its not as good as take it apart though even used oven cleaner to clean my air manifold
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Thought I'd update this -
Removed the turbo this week, vanes were all free and moving as they should, which is annoying! Stuck a load of oven cleaner in there anyway for good measure.
Definitely resolved the stuttering at low revs in 5th and 6th when using a large amount of throttle

Last edited by luk3b3nson; 03-05-18 at 05:57.
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Had similar boost problems, needle would rise then suddenly drop and rise again.

Eventually removed the inlet manifold had it cleaned ( a lot of crap came out ) and all was cured
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Quote:
Originally Posted by luk3b3nson View Post
Thought I'd update this -
Removed the turbo this week, vanes were all free and moving as they should, which is annoying! Stuck a load of oven cleaner in there anyway for good measure.
However it turns out my 210bhp TI has a KKK turbo, which means the previous owner swapped the decent Garrett for a KKK, which is odd! He did mention that the turbo had been changed but it's odd he chose to go backwards. I'm starting to think now that maybe if it was mapped for a Garrett and now has a KKK that this could be the cause of my problem?!
Just looked into this and it depends on which KKK was fitted, general concensus is that the KKK would run out off puff top end when compared to a Garrett, it would also spool up slightly slower?
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Originally Posted by bramblp View Post
Had similar boost problems, needle would rise then suddenly drop and rise again.

Eventually removed the inlet manifold had it cleaned ( a lot of crap came out ) and all was cured
Have you had the swirl flaps removed?
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