Help, RS2 not performing !

[RS2junkie]

Hi,

Would appreciate some advise on sorting out my 95 RS2, it is standard apart from K&N air filter, has 210,000 miles. Have been noticing that it is not as lively as before, not giving the shove in the back at 3,500 rpm and no DV sound when lifting of the throttle.

Today I did a boost leak test and that shows there are none, I cleaned the MAF plug and that certainly made it run smoother but still not as I remember.

Downloaded the codes with VAGCOM and this is what was there
00573 - Lambda - 08-10 Control Limit Superceeded - Intermittent
00561 - Mixture Adaptation - 13-10 Adaption Limit (Nul) Not Reached - Intermittent
00561- Mixture Adaptation - 14.00 Adaptation (Add) Exceeded
00519 - Intake Manifold Pressure Sensor(G71) - 17.10 Control Differential Intermittent

When the block readings (group 2) were opened, the Abs Pressure reading was 1061.4mb and not changing, even when the engine was revving up and down, it stayed at 1061.4.

From this we began to suspect a vacume leak, could see no problems in the engine bay but when I got closer to the ECU I could hear a leak. The hose going to the ECU was in place but bent over, but was not leaking. When I removed the ECU I found a black rigid vacume pipe which had come loose from a joint into a flexible hose heading off to the left side. I fixed this and also replaced the hoze to the ECU, so no more leaks. (I think but have not done a test !)

Took the car for a run but still no significant improvement. I also do not hear the flutter of the DV when I change gear...

Can anyone advise on what to check, is there any common faults to watch out for.

Not sure what next to do ??

Thanks

PAUL

[UrS4boy]

The first three codes point strongly to an air leak after the MAF, perhaps a tear in the boot between the MAF and the turbo inlet OR a boost leak after the turbo. Either way, air that was metered by the MAF isn't showing up at the engine and the Lambda sensor is doing what it can to help the ECU correct the situation but it isn't enough.

Here is some G71 MAP sensor info:

http://forums.quattroworld.com/s4s6/msgs/20417.phtml

The absolute pressure reading didn't change because:

1. the reading was coming from the F96 Atmospheric Pressure Sensor:

http://forums.quattroworld.com/s4s6/msgs/21892.phtml

2. The reading was coming from the G71 MAP sensor and it is either b*ggered OR it is not connected to the intake manifold despite your efforts. Here is some UrS4 info that you can adapt to the RS2 intake to MAP sensor hoses:

http://forums.quattroworld.com/s4s6/msgs/20401.phtml

For additional help, all the labels in this diagram are hot links to more info:

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

[RS2junkie]

URS4Boy

Thank you for the comprehensive reference info, I am studying it closely and will check out what I can. When I did the boos leak test today, I presurised the pipework from just after the MAF to the intake of the throttle body and it was tight....

I am looking for a way to diagnose a leake somewhere in the vacume pipework, there is vacume at the ECU for sure. Is it possible that the G71 has a fault, would that show up on VADCOM ?

I have not checked the piping to the N75 valve, could there be a problem there...

Is there a step by step guide to track down this sort of problem !!?

Thanks for your help

P

[prj]

Control difference is a normal fault code thrown when actual boost is nowhere close to requested.

This is perfectly normal and means OP has a huge boost leak/completely dead dump valve etc.

[fish]

Check the vacuum hose for the dump valve, and then check the dv itself.

[RS2junkie]

Thanks guys, I will check it out and report back

Paul

[re2500]

Sounds like your dv is stuck open or the dv operating hose (little one from the front of the IM) is broken/kinked this would cause leak of pressure from the pressure side to the atmos side of the turbo. But no physical leak when leak test from maf to throttle. If u test from turbo inlet to throttle, you may see a leak back to the maf hose??

[RS2junkie]

Hi

Update

Found my problem, hoze from the top of DV to inlet manifold was split. Replaced and boost is back ! Gauge shows 20 ps1 in 2nd gear at about 5,000 rpm. Reads about -10 hg at idle. Not sure if this is normal but the car feels strong

Thanks to all who have responded to my call for help, it certainly got me sorted out...

Paul

[UrS4boy]

Hi Update Found my problem, hose from the top of DV to inlet manifold was split. Replaced and boost is back ! Gauge shows 20 ps1 in 2nd gear at about 5,000 rpm. Reads about -10 hg at idle. Not sure if this is normal but the car feels strong. Thanks to all who have responded to my call for help, it certainly got me sorted out... Paul

Good news. Looks like fish and RE2500 win today's diagnostic prize.

Prizes can be picked up at Window 17.

Dave F.

[RS2junkie]

Have been running the car for a few weeks and getting used to it again, it feels like a new car. Now that I have a boost gauge fitted I see that it reads 23-24 psi at full throttle in 2nd and 3rd around 5500rpm, on the overrun, it goes negative to about 10-15hg.

I have allways suspected it has been chipped because it gave 335bhp on a dyno about 1 year ago and i know now that it was not at its best. It feels very strong in the mid range and pick up very well anywhere after 3,500rpm.

Question is am I putting the engine under dangerous stress at this boost level, I don't think it has any modifications apart from a K&N filter...

Mileage is 210,000 miles but no sign of high oil consumption and is smooth as silk !

Paul

[prj]

1.4-1.5 bar is standard pressure pretty much.
Your gauge is probably a mechanical unit and they are not that accurate.