Boost stops at 1.4bar - N75?

[newsh]

Hmm, well, either the N75 is clicking but not working or the ECU is not happy about sending boost control. I can't think of any more reasons..

[hunker7]

Hmm, well, either the N75 is clicking but not working or the ECU is not happy about sending boost control. I can't think of any more reasons..

Can I put N75 from my dad's 1.8T? I did put it in, but then the injector died, and I thought it was because of the wrong N75, because when I plugged mine back in it ran fine.

[newsh]

Yes, I'm sure you can use the 1.8t N75, just make sure the long leg goes to the MAF hose and that it's not blocked.

[newsh]

Here's a test worth trying, start the car and let it idle, pull the vac hose off the ECU, you should have a healthy vacuum on it, block it with your finger, you should be able to feel the vacuum.

Connect it back to the ECU and do up the hose clip. Listen carefully to the ecu, it should be silent, if you can hear a hissing then the hose has come off the MAP sensor or split inside the ECU.

In fact, what does you boost gauge read at idle? I wish we'd had a bit more time on Saturday, I should have come out in the car for a drive..

[hunker7]

I'll just visit you again

I will try checking the ECU, and swap N75 over tomorrow. At this point I really don't care how much it costs to fix it, I would be lucky to find what is wring with it.

At idle it shows 0.2 to 0.6 on the dash gauge.

[hunker7]

It is the wiring after all. How do I go about finding where the problem is, I know it's in first cylinder.

[newsh]

I would try and put a multimeter with a beep funktion on the wires, from fuse to connector and from connector to ECU pin. Alternatively inspect the wire very carefully where it goes into the loom near the injector, this is where it gets the most bending around and the wire insulation is hardened from heat cycling. In fact, you may be able to find the break by letting the car idle then moving the wires till it comes back to life. if you think you've found the break then strip back the wire carefully to expose it, solder and sleeve.

[hunker7]

It's not the wire, checked it, tried to move it about no change. Then took the spark plug out, and that hasn't been working at all. I will test the coils and POS.

[UrS4boy]

Improved POS diagnostic and fix info

It's not the wire, checked it, tried to move it about no change. Then took the spark plug out, and that hasn't been working at all. I will test the coils and POS.

You should not be driving the car until this is sorted. The way it is now, if I understand the situation, if the sparkplug is not working but you still have that injector still connected electrically, raw fuel is washing down that cylinder, potentially causing more wear there and then overloading the cats with raw fuel, heating them up more than is a good idea.

Here is a post that I did that will allow you to logically go through a sequence that will determine whether the issue is a POS channel or a coil that has failed:

http://forums.quattroworld.com/s4s6/msgs/153152.phtml

[hunker7]

Thanks I've been rrading through that Just came out to test the coils etc and it runs fine, so i I can't test anything

[UrS4boy]

One missing and hesitation diagnostic

Thanks I've been reading through that Just came out to test the coils etc and it runs fine, so i I can't test anything

Sure you can. Since it is idling okay (ish), it is likely a weak coil. Read this Missing and Hesitation Diagnostics post and focus on the testing of the coils, looking for the one that is weakest. Might be no. 1 for you.

http://forums.quattroworld.com/s4s6/msgs/22611.phtml

[hunker7]

Sure you can. Since it is idling okay (ish), it is likely a weak coil. Read this Missing and Hesitation Diagnostics post and focus on the testing of the coils, looking for the one that is weakest. Might be no. 1 for you.

http://forums.quattroworld.com/s4s6/msgs/22611.phtml

In the article it says when idling or under low boost coil would be fine, but under boost it would play up. Just went for a drive and it runs fine under boost too.. when i removed the spark plug it was quite wet (i washed the engine yesterday) I dried it and that might have fixed it?

[hunker7]

Swapped over the N75, still no luck, but now it looks like N75 is fine, as it boost nicely to 0.6bar, whereas before it was just 0.4. I will take the ECU out tomorrow, open it up and see what's going on in there, check the hose that goes to MAP sensor.

Is there any way of checking the actual MAP sensor?

[UrS4boy]

Swapped over the N75, still no luck, but now it looks like N75 is fine, as it boost nicely to 0.6bar, whereas before it was just 0.4. I will take the ECU out tomorrow, open it up and see what's going on in there, check the hose that goes to MAP sensor. Is there any way of checking the actual MAP sensor?

LOL. 0.6 Bar is NOT NOT NOT fine or nice. It is about 50% of what a stock AAN ECU should boost to. True, the 0.4 bar = mechanical boost only, no N75 connection or failed N75, so 0.6 Bar is an improvement.

What happened to boost leak testing? Did I miss the results or did you ever do it?

G71 Manifold Absolute Pressure (MAP) sensor (any all the Engine Bay Devices needed to run our AANs (and ABYs and ADUs), for the "N"teenth time (recommend bookmarking and reading about the device(s) in question before asking questions here):

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html

[hunker7]

On page 11 you can see what we did and what we found out.

There are no more leaks, so it should hold more than 0.6

By saying 0.6 is nice, I mean it gets to 0.6 nicely, smooth and with no mishaps.