What can cause compressor surge? (159 1.9 JTDm) - Alfa Romeo Forum
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Help What can cause compressor surge? (159 1.9 JTDm)

Chaps, I need help here.

Been trying to diagnose throughout this the forum this but no answers so far. Very briefly, symptoms are:

1 - if turbo is in a situation of high pressure (like going up a hill), if I release the throttle, I get triple "swoosh" sound and the car shakes slightly;
2 - on 1st and 2nd gear, taking it to 3000rpm can cause the surge as well, a bit more evidently;
3 - sound seems to come from middle to right-hand area of the engine bay;
4 - on any gear from 4th-6th, turbo responds promptly, to overtake, etc;
5 - WOT takes the pressure gauge to max 1.5, then drops (which I believe to be normal)
6 - when disconnecting the MAF, symptoms disappear, which I understand is because the ECU defaults to average readings, bypassing the missing MAF.

About (2), engine feels slightly overworked to get to speed, which is why I sometimes stretch it that far (not often). Not sluggish, but nearly.

What has been checked:

- EGR (had a failure warning): replaced with a new genuine one, including official rectangular restrictor gasket
- MAP sensor: cleaned
- MAF sensor: cleaned (was hardly any dirt in there anyhow)
- vacuum pipes: checked, no leaks
- injectors: checked, all within tolerances
- glow plugs: checked, all in order
- DPF: regens normally

So what else do I need to look at before I am dealing with a failed turbo?
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What about vacuum hoses and overboost valve that controls the turbo?

Other than that could be that you have some problems with inlet manifold. Might be related to soot and oil deposits in the manifold.

Do you have diagnostics cable and MultiECUScan?

Try to log:
Engine speed [rpm]
Total fuel quantity [mm3/inj]
Intake air quantity [mg/inj]
Boost pressure [mbar]

Then put the car in 4th gear, floor the pedal at 1500rpm, and push it over 4000rpm... then save the logged data (.csv) and post it here. You can make more than one 1500-4000+rpm run.
You can also try to log the data while the "surge" is happening.
Maybe we will see something useful from the graph...
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On a petrol engine this would be a typical problem with the blow off valve or by pass valve not operating correctly, not opening to be specific. Does this engine have a throttle or BOV? Make sure the vacuum line is connected and that the valve is of course working correctly.
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(Post Link) post #4 of 15 Old 28-08-13 Thread Starter
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thanks for replying. The vacuum hoses were checked, supposedly. I'm still learning my way around the engine.

I'm afraid I don't have the ECU scan. Probably a good investment since it would save me a few trips to the garage.

I'll have it checked one way or the other, because I don't like the way it's performing.

the problem became more apparent after the new EGR was fitted, perhaps because it finally it's doing its job. inlet manifold residue is likely though, since this wasn't cleaned.

i could also change the air filter, but I think checks should come first.
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This engine does not have a throttle valve like a gasoline car. Only shutter valve, that is used to turn off the engine. But during normal operation the shutter valve is fully open all the time. There is also no BOV valve. Diesels don't have them.

There is a possibility that your shutter valve is faulty, but 159 uses "newer" servo operated shutter valves, and you would see and MCSF error on the dashboard if it would not function properly.

Take off EGR, and the shutter valve from the intake manifold, and take a look inside the manifold. Sometimes there is a lot of gunk in there...
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(Post Link) post #6 of 15 Old 29-08-13 Thread Starter
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what is generally a good cleaning method, can it be done with the manifold in place?
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Nope, you have to remove it...
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(Post Link) post #8 of 15 Old 29-08-13 Thread Starter
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I want to try to get hold of a second EGR valve just to discard the possibilty of the new one being faulty (it's a genuine though, bought from alfaworkshop). so i'll have a look then. Maybe i'll also fit the second restrictor valve (the oval one, with 3 holes), although my engine is the 16v. Being a bit of a purist, i've been reluctant to try that mod, since the original engine components should make the car run properly...

'Been paing attention to what the turbo gauge is doing. Taking it to 3000rpm on 2nd gear, the turbo stops just short of 1.6, and when it drops, I finally get the boost. so it seems to be working too hard to get the engine going, in my mind.

Ordered the MultiECUScan cables. Will post as soon as I get the software going.
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Fitting a second oval plate with 3 holes makes no sense... You only need a restrictor plate between intake manifold and EGR valve, to prevent oil fumes entering EGR valve.
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Quote:
Originally Posted by yuri2k View Post

'Been paing attention to what the turbo gauge is doing. Taking it to 3000rpm on 2nd gear, the turbo stops just short of 1.6, and when it drops, I finally get the boost. so it seems to be working too hard to get the engine going, in my mind.
this sounds exactly like a MAF failure to me. They get slow to respond to increased airflow.
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(Post Link) post #11 of 15 Old 08-09-13 Thread Starter
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OK, here is the data from the MultiECUScan.

Trip 1: surge (decelerating) was evident at 45sec, 115sec, and 380sec.
https://docs.google.com/file/d/0B3E6...it?usp=sharing

Trip 2: one 1500-4000rpm run in 4th gear (difficult to do in local traffic conditions, but there you go)
https://docs.google.com/file/d/0B3E6...it?usp=sharing

Trip 3: surge on acceleration right at the beginning
https://docs.google.com/file/d/0B3E6...it?usp=sharing

Annoyingly, the surge symptoms haven't been very pronounced while logging (I hear the swooshy sound of the surge, but not violent enough for the car to shake).

One useful reference: what should be the difference between boost pressure and desired boost pressure on idle? Mine is 1200mBar/1000mBar.

Last edited by yuri2k; 08-09-13 at 16:52.
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I'm almost 100% sure your MAP sensor is faulty (boost pressure sensor). That is most evident in idle, you should not be getting 1200mbar at idle, this is impossible turbo cant create any pressure at idle. On most cars you see values between 970-1020mbar in idle.

Also at acceleration the airflow numbers are low, that confirms that measured boost is not as high as ECU thinks.

Change MAP sensor and try to make the logs again.

You should be getting around 1000mbar pressure at idle, and airflow at full load should be over 1000mg/inj between 2000 and 4000rpm (peak is over 1100mg/inj)...
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Double post...
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(Post Link) post #14 of 15 Old 11-09-13 Thread Starter
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Ordered. Will post back when I have some results.
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Did you ever get to the bottom of this? its gone very quiet which hopefully means you sorted it as you never came back to ask any more questions.

I have had my 159 a few months and been looking for info and it seems like I have something very similar happening, I originally took it back to the supplying dealer and they said a turbo pipe had come loose and they had tightened it back up, it did seem better but came back after a while.
I had an engine management light come on the other day I cleared the error (turbo boost pressure - iirc, I have the error saved on my home computer) and the EML has not come on again but now it seems worse than ever,

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