Have you tested the maf output as per this guide http://www.vwt4forum.co.uk/showthread.php?t=87513 ? getting 455 at idle doesnt tell you anything really you need to floor it in second I think and make sure maf value (box1) rises to above 700.

 

Morning.


I have not tried that test yet.


Will try later when I can get someone to come along with me to press buttons on the laptop whilst I drive.



Thank You

 

you can put the laptop on the passenger seat,floor etc and then choose the data you want to monitor and then use the log button, go for a drive and then when you come to a stop, stop logging and then the file will be saved to a format which can be opened with windows excell, you can then see the actual vs expected results.

 

Update.



Just managed to run the test on my MAF using VCDS.



Didn't manage to get 100% load or over 3000 revs due to traffic ( never ending )




The readings for group 10 were:-


1. 860 mg/st
2. 999,6 mbar
3. 1897.2 mbar
4. 82% load



The readings for group 2 were:-


1. 2856/min
2. 100% load
3. 0
4. 90 degrees C




Two fault codes have reappeared following Auto Scan.


17564 G71 Manifold Pressure Sensor P1156 -35-00 Open short to ground.

17569 G72 Manifold Temp Sensor P1161-35-00 Open short to plus.




Is it possible to test these G71 and G72 valves?.

What detrimental affect could these faults have on the performance / fuel economy of my T4?.




Thanks

 

From what I understand (not much!) with the engine off, those values look about right to me; no boost would leave the sensor reading atmospheric pressure approx. 1 bar at sea level. So a little less above sea level dependent on your absolute height.

At idle, you'll be seeing very little (if any) so again. Around atmospheric should be about right. A little lower though as the little exhaust gases that are expelled will spin the turbo a tad. At 3000 revs/m, with you kicking out a fair amount of exhaust gases from the head; I would expect to see more than 999mbar at 100% load and from this codes I would assume that the MAP (or something along that circuit) is toast.

That being said, I'm nowhere near 100% confident in my assumptions.

I'll give it a look when I'm 100% sober in the morning.

Also, what MAP/IAT sensor are you running? The all-in-one later one perchance?

 

With a non throttled / egr closed diesel engine at idle, divide the cc by the number of cylinders and MAF mg/st (milligrams per stroke) should be near, if MAF is good.
2500cc / 5cyl = 500 mg/st

I take it in group 10 blocks 2 and 3 are for actual and desired, that to me would say MAP is goosed...

 

Could this also be a split turbo hose if requested boost is low?

 

I'd have thought actual boost would suffer from a split hose rather than requested?

I am intrigued by the code that the IAT sensor is throwing.

 

Absolutely.....

Edit, didn't see requested, so no.

 

My 2.5 TDI has had the EGR cleaned and blanked.




The MAP sensor is located as shown in the photo:-

Not sure where the Manifold temp sensor is located.


I have had a look at the wires around the MAP and followed them to the loom but cannot see any broken wires.


Is it worth checking inside the ECU to see if any wires have broken or worked loose?.

If so is there a How To Guide on removing and checking inside the ECU?.


Some of the small diameter pipes look a little rough but I haven't found any leaks yet unless they are perished.


Would it be worth changing those small diameter pipes and if so what diameter and lengths of pipe would I need?.






Thanks

 

Ah ha! That's the integrated MAP and IAT sensor.

I definitely reckon it's had it. Try replacing it and the hoses and see if that cures it. Search by the Bosch part no. online and avoid going to the main dealers for one. I found that the discrepancy in prices was quite large.

 

Thanks for the replies.


£35 on the Bay of E for a new genuine 038 906 051 B sensor.


Does that sound like a reasonable price please?.



Is it possible to buy a ready made set up of pipes and securing / jointing clips for the AJT engine and if so does anyone have a link please?.


If I were to just buy lengths of suitably sized small bore piping then what diameters would I need and what overall length of each size please?. Can I also buy new clips to secure the piping to the joints?.


Has anyone done a " How To Guide " for replacing the small bore pipes or could you provide a link please?.



Thanks

 

For a new genuine one, that's a good price.

 

I have ordered a new MAP and will do a VCDS Auto Scan once it is fitted.




Hope to order and fit new Vacuum Hoses too as the original cord covered ones are looking rough ( over 11 years old now ).



Thanks

 

Hoses thread here........

http://www.vwt4forum.co.uk/showthread.php?p=2509966#post2509966

T:

 

Thanks for the link.



I have just ordered 3 m of 3 mm ID and 3 m of 4 mm ID Silicone hose.



Hopefully that should be here early next week so I can start replacing the old vacuum hoses.T:

 

Does your van go into limp mode?

I had a problem where it would occaisionally go into limp mode, long story short it was the loom.

As the plug and wires lead to/from the MAP sensor (temp too, integrated twin sensor) and dissapear into the main loom adjacent to the expansion tank, peel back the outer corrugated protective sheething from the main loom and the feed to the MAP sensor, I had two wires breaking down, just where it bends through 120 degrees from the main loom to the tail, the sections were replaced and spliced and it's been all good since.
(I bought a new sensor from VW, not needed VAG com pointed to the sensor, what was I to know LOL: )

Chris

 

I will check the condition of the wires as the man above mentions.



Did you have to peel back quite a lot of the cable cover to find the faulty wires?.




Thanks

 

My T4 has never gone into limp mode yet but I was concerned when VCDS showed the 2 faults.

 

All of the sheathing on the spur, and about 40mm up and down from the join, the protective sheething seperates easily enough and it was obvious.

My problem was intermittent, fine for a while then iffy, I thought it was the sensor breaking down (VAG com indicated)

It was a short in the power feed and another cable, rubbing on the bend I think wore on the insulation.

Cheap to check to eliminate, it just read that you perhaps had not gone that far into the main loom.

Let us know how you get on.

Chris

 

Hi Did you sort it as my 2007 VW 1.9TDI T5 goes into limp mode when i start for first time but then fine when i restart its then fine. changed the n75 valve and now its showing fault code of boost pressure sensor problem, any ideas please? thanks