P1238-Air Quantity 2 - Alfa Romeo Forum
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(Post Link) post #1 of 11 Old 19-02-12 Thread Starter
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P1238-Air Quantity 2

Hi,
i have a problem because error in subject is happening. If i clear the error with FiatEcuScan, it shows again after few seconds.
If i monitor "Desired intake air quantity" and "Intake air quantity", intake is all time double then desired (see attached graph).

I check EGR and it was stucked in open position. After i clean it, opening/closing is ok.
MAF sensor i change with another one, from another car, and error still shows. I also clean MAP sensor.

Pipe between turbine and intercooler was broken, and i fix it. I check other pipe from IC to intake.

My question is, why in intake is double air quantity? What else i have to check, and what might causing it?



Car is Alfa Romeo 156 1.9 JTDm 16v (2004. year).

Thanks

Last edited by gurdich; 23-03-12 at 21:43.
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(Post Link) post #2 of 11 Old 23-03-12 Thread Starter
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Now, this error only appear when car is idle. At other revs, everything is ok.
With FiatEcuScan i measured voltage on MAP, and it is (when idle) between 1.9 and 2.5 V. Maybe that is not ok...very big difference.

On other revs, for example, 1500 rev....voltage reading is 2.5 or 2.6.

Any ideas? I think that MAP is not ok, and shows more voltage when idle, than really is.
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Maybe the egr is stuck in the closed position/or blocked with soot(or egr cooler blocked but never heard of one )log desired air , actual air and egr %.
You would expect to see actual air to drop to the desired values (less than 400mg/i)as the egr opens 30-40%. Blip revs up and egr shuts maybe 0-4%, the idle actual air will be around 500mg/I until egr opens again and actual should drop again to under 400.
Ecu is expecting less air from maf value because the 100+mg/I difference should be coming from egr valve/ exhaust.
Was that graph stationary just revving or driving?
Try logging a bit of driving and slowly accelerate 1500-4000 and see if actual follows desired better, egr should be shut so should follow quite closely .
Then log at idle if I remember right egr cycles every couple of minutes when just idling, so you'd have to watch or log for say 4 or 5 min with no revving.

Last edited by sussexa; 24-03-12 at 08:03.
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(Post Link) post #4 of 11 Old 24-03-12 Thread Starter
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thanks...i will try do it today.

and, what about this P1238 error, that appear only when idle?

on all other revs, everything is ok. error will not appear.
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Here's good pic from an old log showing it cycling egr opens airflow drops, set time after egr shuts set time egr opens all at idle( but after engine warm
To cycle like this)
http://img821.imageshack.us/img821/2...rcoldstart.png
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Member car:

147 JTD, YZF600R

Clean your EGR, but if that does not make a big difference, it might be worth cleaning the EGR Heat exchanger - when I refitted mine, I found it was nearly completely clogged.. (Soak in oven cleaner/ammonia dissolves tha carbon) the small bore tubes that run within the coolant jacket os the heat exchanger block up very easily due to their size.

Its a bit fiddly, but may be worth it!, I had only done 70K..
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(Post Link) post #7 of 11 Old 24-03-12 Thread Starter
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Here is attached output I did few minutes ago.

I start the car, is idle, and EGR is open. I think it is open because actual air quantity is more then desired. Difference comes from EGR.

At 170. second I move the car and EGR was at 30%-40%. I stop after 3 seconds and EGR was closed (100%), and suddenly opens at 181. second (1%).

At this moment error P1238 appear.
Attached Files
File Type: xls export.xls (52.0 KB, 30 views)
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100% is fully open not shut, fully shut it looks like yours shows 1%, mine shows 4% when fully shut.
Those 560mg/I when egr at 1% look about right compared to mine , as the egr opens the airflow drops to 380ish - 350ish that looks about right also but it doesn't stay low enough for the ecu and the egr keeps opening more and more till 100%.
As said above clean and ensure the egr is opening enough, not sure how stefz tested egr cooler (starting car with egr valve off, and feeling for exhaust flow at supply to egr pipe)
One thing doesn't look right are those desired airflows down in the 270's look too low, plus the value isn't dropping when it expects value to drop with egr opening?
Has this car been remapped at all?
What ecu code are you eg I'm edc16c39 , are you connecting to the right ecu in fes.

Last edited by sussexa; 25-03-12 at 10:26.
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(Post Link) post #9 of 11 Old 25-03-12 Thread Starter
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Car is tuned with Rapid module from DIM sport and Im using it for 7 years.
Engine tuning parts - Dimsport Technology

EGR i cleaned very well. All soot is out, and with finger I can move valve very easy. Other side of EGR which is in plastic, I didnt open. Didnt drill a hole 3mm on opposite side to get out shaft for cleaning.

When I disassemble EGR I can see that shaft from plastic part go out for about 5 milimeters and easy with fingers I can push it back in.

I use in FES edc16c39.
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maybe try a reset learn't values in fes , see if it changes the desired airflow values at all, possibly got used to egr blocked and split boost pipe?
or a complete ecu reset?
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(Post Link) post #11 of 11 Old 25-03-12 Thread Starter
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i tried now. unplug battery for 1 hour. values in FES are the same.

all this happen after split boost pipe.
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