URS6 Way Too weak!!!

[K7ERG]

I had similar on my old astra turbo. Motronic ecu also. Cut power. It turned out the pipe to ecu was partly shut off by a elbow rubber connector to ecu being doubled back. It also had wiring issues to knock sensor. Replaced loom and found a split in the shielded wire

It took a fair bit of time to sort out......well find the problem.

[UrS4boy]

This might not have anything to do with knocking but it could do with running down on power:

Have you pressure tested (wait for it), the green pressure/vacuum tubing that goes from the AAN intake manifold to the ECU (via a moisture trap). If it had a split, it would hold boost to certain point and then the little hose would open and dump boost. As a result, the ECU would not tell the injectors to add more fuel (which could cause you to run lean and, hence, pinging). Do you have a boost gauge so you can tell us what boost levels you are getting.

What I am talking about are the green ones in this diagram:



They start at the intake manifold and then head to a moisture trap (in this case an UrS4 on the firewall):



or in the case of the UrS6 down in the footwell (like this LHD passenger side):



Once through the moisture trap, the hose connects to the ECU brass nipple and hence the MAP sensor, as shown in this photo of an opened Motronic ECU:



Unless you have a boost gauge and you have seen over 20 psi (say 1.5 Bar gauge) boost, AND you are sure you have no major boost leaks, you might have a leak in this intake to MAP sensor green plastic pipe/hose. To test, I would pressurize it to 25 psi (1.7 Bar) - if it doesn't hold, you *might* have your answer.

[HMS-S6]

What about the knock sensors? are they new? tightened to the right torque?

Thanks Jamo. But the sensors were replaced for new and to make double sure i took them off the good runner i had at the time and torqued to the correct setting.
Am i right in thinking that 14 btdc is more retarded than normal??

I'm running out of ideas, i've checked and triple checked camshaft timing, fuel pressure and for boost and vacuum leaks. What the hell else can cause knock?

[HMS-S6]

I know we are running out of ideas but this thread is illustrative of a simple mistake that has similarities with your problem:
http://www.s2forum.com/forum/showthread.php?t=58639

Thanks for the thought but on my AAN the run-on connections are two separate spade connectors. Plus all readings like that are spot on.

[UrS4boy]

What about the knock sensors? are they new? tightened to the right torque?

Good one Jamo. If the knock sensors (or even one them) are Fubar'd, the ECU dials back the timing (6 deg) and probably boost because it has no way of controlling pinking (pinging) without the G61 and G66 knock sensors.

http://forums.quattroworld.com/s4s6/msgs/21047.phtml

[Jamo]

What about the knock sensors? are they new? tightened to the right torque?

[twoqu]

I know we are running out of ideas but this thread is illustrative of a simple mistake that has similarities with your problem:

http://www.s2forum.com/forum/showthread.php?t=58639

[HMS-S6]

Been out in it today to log the data on the vag-com and it seems it hates the warm weather even more!!!

Timing retarding back to 15 btdc this time as opposed to 18.5 btdc when it was pulling well t'other day. What the F**k is causing it to run so lean?? Fuel pressure checked again and its still bang on!

Again if someone reading this, knows their stuff and is willing to look at it, please step forwards!!

[HMS-S6]

Which specialist in the UK knows this kind of stuff the best????

[UrS4boy]

Looks like there is no substitute fuction for the G4. It's only used for starting and not needed for engine operation. Althought that doesen't explain what happens to your vehicle when you unplug it! Its the hall sender that ignores the knock sensor.

Well there are some cross-redundancies. The G4, G28 and G40 are all needed to start the car. If the G40 fails while the engine is running, the ECU will use the G4 signal. If the G40 is good and the G4 fails, the ECU will carry on based on the calcs it does. However, it won't restart. I am not sure what happens if the G40 fails first while running and then the G4 fails after that. Personally, I would duck and hide because you are about to be struck by lightning.

[twoqu]

Looks like there is no substitute fuction for the G4. It's only used for starting and not needed for engine operation. Althought that doesen't explain what happens to your vehicle when you unplug it! Its the hall sender that ignores the knock sensor.

[twoqu]

What about the injectors themselves. Certaintly a faulty injector might explain an intermitant weak condition but not explain why it runs better when the crank sensor signal is removed!
You will have to look at the subsitute function for crank signal. Seem to recall it goes to some default and ignores the knock sensors. Of course that might all be related.

[HMS-S6]

Pre-detonation (pinging or pinking) under those circumstances suggests lean conditions and/or a timing issue. You say you have perfect fuel pressure but when/how are you measuring it? With a 4 Bar FPR, you should have 4 Bar (58 psi) plus boost pressure at ALL times, e.g. at 22 psi (1.52 Bar) boost, the fuel rail needs to have 5.52 Bar (80 psig). Otherwise, the injectors will be supplying less fuel than the ECU expects them to do and pinging will occur until the ECU gets the feed back from the G61 and G66 knock sensors.

If your fuel pump is good and the fuel lines are somehow kinked, you might have a FPR problem. Click on the FPR label in the upper middle of this diagram (all the other labels are live links as well):

http://members.shaw.ca/speedtek/UrS%...ice%20Map.html

I checked it by fitting my gauge in the feed pipe to the injector rail. It has a faultless 4bar plus boost everytime! This is why its driving me mad, by all tests it should be running perfect

Even though i'm wanting to cure it myself, i'm at the point where i'd farm the job out if only i could find someone to do it?

[newsh]

The other thing to look for is a leak on the vac line to the FPR and a blocked fuel filter but I guess you've already been there.

[newsh]

My avant used to hold back after a full throttle run through the gears and then lifting off the throttle then back on it again, the bores were glazed so I guess as I came off the throttle it would suck in some oil which would cause it to ping. Hone and new rings cured it.