Some MAP/MAF Analysis please

[tjg04]

Hi,
I've been having some issues with my '97 A4 Avant. It's a 1.9TDi (110PS) AFN engine.
I've had it drop into limp mode a couple of times. Only when the car's fully loaded and I floor it in 5th on the motorway up a hill. Can't reliably recreate it every time, and cycling the ignition clears the problem.

A scan with VAG-COM gives the 00575 Intermittent error. So I took it for a little spin on the motorway and took some logs.

Firstly block 11:


As you can see, my actual boost pressure lags behind the requested pressure and never reaches it. Does this point to a boost leak, or is it normal?

Secondly block 03:


This is MAF actual vs RPM for the same periods of acceleration. Are these readings low? I'm not getting any errors from the MAF on the scan.

Would appreciate some experienced eyes on this.

Also, I've noted a small dip in MPG if that indicates anything??

Ta

Tom

[tjg04]

Think I've solved my problem,

Suspecting a boost leak I checked all the pipework to and from the intercooler, but no splits or tears.

I improvised a boost leak tester as follows. Got hold of an old bicycle innertube (free from the bike repair bit at halfords) and cut it 3" either side of the valve. Streched one end over a 40mm pipe plug from Homebase and clamped with a jubilee clip. I then stretched the other end over the turbo inlet and clamped that with a jubilee clip (total cost £3). I then attached a foot pump to the valve of the inner tube and began pumping.
Can provide photos if anyone's interested in making their own. Foot pump really isn't adequate for building the pressure too high, and no doubt the inner tube would stretch too much with high pressures. However it found my leak pretty quickly! And the inflation/deflation of the section of inner tube is a useful indication of a leak.

The narrow pipe that runs from the hose at the back of the engine to the MAP/ECU had been rubbing down behind the engine and and formed a tiny hole. This looks to be a real PITA to change but there was enough slack in the pipe for me to cut it out and clamp back onto the braided flexible.

Car runs much better now, and hopefully the MPG returns with it. Hopefully this was the cause of my slow oil leak too!

Also gave my MAF a once over with brake cleaner too, though don't know if it needed it.

Thanks for looking!