Td5 Engine Surging

I think one of my tests may have been incorrectly done. I connected the black tube from the wastegate modulator to the white stripe tube from the air intake pipe.


I think the bypass should be to take the pipe with the blue stripe off the bottom of the solenoid boost control modulator and connect it to the black pipe from the wastegate modulator.


After having done that I could not reproduce the original symptoms and deduced that I should replace the solenoid boost control modulator. So, this is now fitted and I went for a quick test run.


All went well and the engine ran smoothly until I floored the accelerator pedal up a short hill.


Revs went to about 3,300 rpm and then the engine began to hunt - 300 rpm surges and no increase in speed.


Any ideas what could be causing this?


Cheers,


Franz

for bypass you have to put the pipe from the bottom of the modulator directly into the wastegate valve(the one on the turbo with the rod attached)... this valve has a membrane within which might leak too, not very common but possible

Over boost symptom!

Boost now working properly and going over cut point or MAF going out of range on high air flow.

Throw the Nanocom on and start recording

Thanks Mike, I'll record some data tomorrow. Problem is I can't do anything with the files as I can't convert them to csv format.


Also, MAF is OK, I checked it against a known working MAF.


Strange that it is suddenly over boosting

Wastegate now functioning fully, MAF slightly out of range at top end, sensors all cleaned so running back at their best.

Quote:

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Originally Posted by Franz

Thanks Mike, I'll record some data tomorrow. Problem is I can't do anything with the files as I can't convert them to csv format.


What could be causing this sudden overboost?

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I will find you the file to read them, or send me the file output

My MAF measurements compared to a known good one:


Existing MAF
Pins 1 & 2 = 16.72 K Ohm
Pins 1 & 3 = 28.54 M Ohm
Pins 2 & 3 = 28.20 M Ohm
Known good MAF
Pins 1 & 2 = 16.83 K Ohm
Pins 1 & 3 = 27.35 K Ohm
Pins 2 & 3 = 27.30 K Ohm

Quote:

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Originally Posted by Franz

Revs went to about 3,300 rpm and then the engine began to hunt - 300 rpm surges and no increase in speed.

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Franz, when you get these symptoms, what are the MAF and MAP readings bouncing between? Do either look to be going out of range as Tombie has described?

DiscoDB,


On the first occasion the MAF maxxed out at 672, 0, 0, 0 ,0, 0 then back to normal readings. Second occasion it went to 683.5, 540, 0, 0, 0, 0 then back to normal.


AAP readings would go from around 101 down to as low as 95.


I've managed to convert the Nanocom file and have uploaded it.


Cheers,


Franz

Wiring loom fault / connection issue causing an open circuit perhaps? caused by engine movement due to accelerating? Obviously just a (wild) guess....