EGR woes

[slow_nick]

I've got an intermittent fault which is throwing the car into limp mode, a VCDS scan shows P0401 EGR flow insufficient. I assume the valve is blocked up with ****e and the solenoid is failing to actuate sometimes.

 

Most times I get the limp mode it disappears when I re-start the engine and I won't see it again for weeks. However this past weekend it wouldn't go away no matter what, even after a decent 50 mile high RPM blast. However this morning there is no sign of the fault or limp mode, so I did some measuring in VCDS this morning idling the engine from cold and it was showing:

 

EGR specified value 40.8%

EGR solenoid valve actual value 58.81%

Exhaust mass flow of EGR 16.6 kg/h

 

So I assume I was right in that the solenoid is not actuating fully and sometimes may get stuck completely. Is there anything I can do to reliably fix this other than replacing the EGR entirely? I have been told that cleaning it doesn't really work and it's just a temporary fix. I've been looking around and there are plenty of companies offering an EGR delete at a much lower cost than replacement, and I am very tempted.

Edited 6 February, 2023 by slow_nick

[J.R.]

Go into Output tests or whatever the term is and command the EGR whilst watching the measuring blocks for specified and actual value,( it may do the latter for you) to see if your theory is correct.

 

The ECU does not measure the EGR flow, instead it looks for a decrease in mass air flow corresponding to the calculated EGR flow so other suspects could be the MAF sensor or the throttle valve or that the vehicle has previously had an EGR delete which is now causing problems.

[slow_nick]

5 hours ago, J.R. said:

Go into Output tests or whatever the term is and command the EGR whilst watching the measuring blocks for specified and actual value,( it may do the latter for you) to see if your theory is correct.

Yes OK i'll try that, thanks.

 

How can I test the MAF or throttle valve?

 

I'm fairly certain it hasn't had an EGR delete, and I don't think it has had the emissions fix yet either. I have zero intention of getting the emissions fix too.

Edited 6 February, 2023 by slow_nick

[slow_nick]

I tried the output test and it didn't work, just said "control unit refused command" or something like that. Tomorrow I'll log the values on the drive to work