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Discussion Starter #1
Hi chaps, got an issue with my 2006 1.9 GT. Would appreciate some thoughts as to whether I'm thinking on the right track or not.

To start, the difference between the blanking plates with holes and without holes, is to allow some air flow, so an error code is not detected. I believe the EGR valve does not have any sensors to detect air flow, it just opens or closes or gets stuck!

So, the error codes are detected by the map sensor?? am I right? the map sensor is a dual sensor which reads temperature via the bulb bit in the cage and pressure via a little hole just below the cage. So if there is no airflow into the manifold, the map can sense this, either via a change in temp or pressure or possibly both. The map expects to see some airflow at low revs and not at high revs ...is my understanding of how the egr works.

So my problem, is that I have solid blanking plates with no holes, at both points on the EGR (diamond and rectangular shaped). I was getting the egr error code (P0401) and then it stopped being recorded! You might think yay!! but the car is down on power a lot!

I'm not getting a map error code ...does it have one??
Does my theory work, as to why no egr code ie. the map is broken. This in turn could be the reason for reduced power.

Does anyone know if the map affects the fueling in some way? (I know the maf is usually in charge of this)

Please pick holes in the reasoning or any feedback is appreciated.

Cheers
 

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To start, the difference between the blanking plates with holes and without holes, is to allow some air flow, so an error code is not detected. I believe the EGR valve does not have any sensors to detect air flow, it just opens or closes or gets stuck!
True - there's no feedback to the ECU about flow from the EGR valve itself.

So, the error codes are detected by the map sensor?? am I right? the map sensor is a dual sensor which reads temperature via the bulb bit in the cage and pressure via a little hole just below the cage. So if there is no airflow into the manifold, the map can sense this, either via a change in temp or pressure or possibly both. The map expects to see some airflow at low revs and not at high revs ...is my understanding of how the egr works.
MAF sensor I believe, not the MAP.

ECU expects to see a drop in clean airflow when the EGR valve is open, hence looks for a step change in the airflow being reported by the MAF sensor.

Manifold pressure should remain relatively stable, as the VNT system on the turbo should adjust to maintain the same manifold pressure independent of EGR operation (it's a separate control loop I believe).. Since the exhaust pressure in the manifold is nice and high, the VNT system lowers the turbo output to maintain the same manifold pressure, hence lower clean airflow..

Fitting restriction plates works because it puts a restriction/pressure-drop in the EGR flow, so you get less diesel fart in the intake, hence more lovely clean air to maintain the same manifold pressure... But that hole is enough that the ECU recognizes a step-change in the MAF reading between open/closed..

Your situation (no EGR error, but down on power) would indicate MAF problems rather than MAP... It's worth popping the MAP off and giving it a clean up just because it's so easy to get to, but I'd be looking at the MAF straight after it that doesn't fix it.. In fact just try disconnecting the MAF sensor and going for a drive... It'll idle rough, but if you'v got the mid/top end power back then that's your problem.
 

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Discussion Starter #4
Thanks Editor! ....problem is, its just got a brand new bosch maf fitted! I also tried disconnecting it before purchase of a new maf, which also made no difference. The map was cleaned but its 10 years old.

How does the maf report a change in airflow? I thought the piping to the egr is all after the maf. I was thinking the maf only detects air that has come via the air filter? Sorry i'm not so familiar with the entire system ....could you explain that bit please.

Thanks


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Discussion Starter #5
I just read some more on the internet ...I think I understand a bit more now about how the maf records the volume of air that is able to pass through it.

So, back to the lack of EGR error code, even if there is a leak anywhere along the pipe from the exhaust manifold, through the egr cooler to the egr valve ....the maf should still register that there has not been a change in air flow and throw a code (because an air leak is constant).

Any other ideas of why no egr code?
 

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I get p0104 consistently for last 3 years since blanking. Something must have change with your map, maf, vanes, vacuum, turbo hoses or intake hoses.
The only time my p0104 stayed off was when I had a cracked vacuum hose to the vnt. The car was underpowered at low revs and smokey but no fault code was generated.
I don't really know how the egr operates. I think it opens at low engine % load. The load must be a calculation made from maf and fuel rail pressure.
Anyway something's not right so start with the cheapest and easiest; leaks and work your way towards sticking vanes.
 

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Thanks Editor! ....problem is, its just got a brand new bosch maf fitted! I also tried disconnecting it before purchase of a new maf, which also made no difference. The map was cleaned but its 10 years old.

How does the maf report a change in airflow? I thought the piping to the egr is all after the maf. I was thinking the maf only detects air that has come via the air filter? Sorry i'm not so familiar with the entire system ....could you explain that bit please.

Thanks


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Yep, EGR joins the manifold after the MAF sensor. But both the EGR system and clean air/MAF system end up in the inlet manifold where the MAP sensor see's them combined.

Lets say your ECU wants to maintain 1.5 bar boost pressure in the manifold. In order to do that, there needs to be a sufficient amount of air/exhaust-gas being forced into the manifold to make up for that which is being consumed by the engine.

If you run with the EGR fully closed, then you need 100% of that air via the air filter/MAF/turbo. With the EGR open, you get a flow of diesel fart back into the manifold under pressure, hence you might only need 70-80% of the same flow coming from the filter/MAF/turbo side (%'s are completely made up by the way!).

ECU looks for that change from 100% to 80%, as it expects that when the EGR opens up the clean air being registered by the MAF will reduce.
 

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Discussion Starter #8
Thanks! that makes sense. I was hoping to have found an option.

If anyone has any ideas on the lack of egr error code, i'm all ears!
 

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Low boost is removing the p0104 as now map, maf, throttle sensor and fuel pressure are within parameters.
If the car boosts as it should (but with a blanked egr)then excess flow at the maf indicates that the egr is closed. Hence p0104.
Do you still have a fuel booster box. This might be complicating things.
 

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Discussion Starter #10
Low boost is removing the p0104 as now map, maf, throttle sensor and fuel pressure are within parameters.
If the car boosts as it should (but with a blanked egr)then excess flow at the maf indicates that the egr is closed. Hence p0104.
Do you still have a fuel booster box. This might be complicating things.
Cheers mate.

No I removed the tuning box to ensure no skewed readings. Apparently, the car is boosting but a bit below what is expected. We (as in the garage) is going to do a compression test next week. It starts and runs fine, fuel pressure is ok, injectors are within tolerance, just been deflapped and manifold cleaned (no flaps missing) ....it revs slowly and won't go beyond about 3k.

The garage swapped the VNT solenoid and the results looked ok. If its not a compression problem, then it wasn't too clear which way to go next.

(The swirl flap motor has been detached from the de-flapped manifold and secured somewhere else. We think its broken because its giving an error code. It seemed unlikely that this code could cause a limp mode, but we may replace it, just to be sure)

The egr code bit was maybe a route to diagnosing the underlying power problem.
Maybe we should look at the boost readings again?

thanks for the help - really appreciated
 

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I would start looking at the vac hoses first and then turbo itself at this point, sticky vanes perhaps...I can't imagine you will be down on compression, these JTDm lumps are very solid and can handle a lot more power than were designed for..

as you said it's not boosting as it should QED look at turbo related stuff, you have ruled out sensors. if the vanes are stuck then it will over boost and go into limp mode, this will clear after a re-start most of the time...this is exactly what a faulty maf does as well and a stuck EGR, so it can get confusing..if your vac hoses have splits then you will also get these symptoms but normally without a code as all sensors will be reading within expected parameters. but the due to the lac of vacuum the vnt actuator will not work as it should.

good luck and I hope it proves to be an easy fix.
 

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Discussion Starter #12
I would start looking at the vac hoses first and then turbo itself at this point, sticky vanes perhaps...I can't imagine you will be down on compression, these JTDm lumps are very solid and can handle a lot more power than were designed for..

as you said it's not boosting as it should QED look at turbo related stuff, you have ruled out sensors. if the vanes are stuck then it will over boost and go into limp mode, this will clear after a re-start most of the time...this is exactly what a faulty maf does as well and a stuck EGR, so it can get confusing..if your vac hoses have splits then you will also get these symptoms but normally without a code as all sensors will be reading within expected parameters. but the due to the lac of vacuum the vnt actuator will not work as it should.

good luck and I hope it proves to be an easy fix.


Thanks Joey ....i hope an easy fix too!

Its not smoking at all and if it went into overboost, i think the error codes would have been logged. I was fairly vigilant in recording codes when the problem intermittently started. First impression was that the boost was off a bit, but not enough to warrant the lack of power. So we focused elsewhere.

Dan at autolusso penrith is dealing with it, so its in capable hands, but the obvious things seem to have been checked, so far.
 

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cool,mate, have heard only good things about Dan, I very much doubt he won't have checked the obvious stuff..

BTW if it does turno out to be turbo related just go and do the hybrid upgrade me and Damein have..it's a blast...:thumbup:
 

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Discussion Starter #15
Pretty sure swirl flap motor problems will put the car into limp mode. Plenty of threads on here confirming that.
Thanks Alexie. I've read every swirl flap thread I think! - but i'm not aware of one of them confirming the motor has the capability for limp mode.

If you have any threads that you can pick out I would be grateful.
 

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Discussion Starter #17
Thanks Alexie ....i have ordered a used motor today, but in the mean time Dan has acquired a spare one which he will test. I will report back on the findings, as it will be useful for others to refer too.


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I speculate that: With the swirl flaps removed most people chose to have a remap because performance is lost at low revs. With the swirl flaps gone the engines original map is certainly going to be receiving data it's not expecting (particularly at low revs). In your case the data is too far from the programmed parameters and the car goes into limp.
Normal advice would be that you should only chip your car when everything is running sweetly already. However, in the case of an engine modification such as the swirl flap removal a new map is needed to account for the new intake gas movements.

Just a theory: Fortunately I have a non swirl flapped 156.
 

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Discussion Starter #19
Great news chaps ....its fixed! oh the relief

So it appears that the broken swirl flap motor was limiting the revs to about 3k. But I also had a dodgy VNT solenoid that was contributing to lack of low down power. The VNT issue wasn't causing any error codes, maybe because it needed high revs before it tripped?

The EGR error codes are back lol
 

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Good news. Thanks for posting the outcome. Always difficult when more than 1 item is playing up but hopefully this will help others diagnose.
 
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