Limp mode

[cptk]

I know this subject has been covered before, probably many times, but I’m now at a loss and having spent nearly £450 already I am ready to drive the car off a cliff, if I had one nearby.
I have a A4 1.9 tdi 130 the car has been going into limp mode, the first thing I did was to have it checked on a computer. Several fault code came up suggesting a vacuum problem. I know the turbo is ok as I have had this checked, and you can hear it whistling as you accelerate. My mechanic checked all of the hoses to make sure that none of them where leaking. Also double checked the turbo and no fault was found there.
I was told that the best thing was to take it to an Audi dealer and have them use their computer test equipment as there’s give a more detailed test. What showed up was a EGR fault, and one of their mechanics advised me to replace it, as it was better to do that then strip and clean out the old one.
However despite having the new one fitted (not by the dealer, but by a good independent garage) and having the faults cleared, I still have the same problem, the car goes into limp mode. The only way I can clear it is to switch off and on the ignition for a few seconds and that clears it until minutes later it goes back to limp mode.
Audi tell me that you have to clear the codes several times before the codes have properly cleared from the ECU completely, mmmm, not sure if that makes alot of sence... Also after again plugging in a friends computer, it showed that the fuel pressure sensor was reading too high, I have ordered one to see if that is the problem.
All Audi suggest is for me to bring the car into them and let them spend a day on it, the only thing is that is going to be mega bucks!
Can anyone help? Please

Thanks, Karl

[hagis]

N75 valve?

[Deck84]

Hi Karl i had similar problems with my a4 it turned out it was a combination of really dirty diesel and a chocked EGR valve.

Might not be a bad idea to dip your fuel tank and see if the diesel is clean. If its dirty have it flushed clean and get the EGR cleaned out again.
Was a right pain for me as my independent mech could't figure out what it was for a while. It would be in with him for a few days id get it back drive fine for a day or so and then it would go back i then told him to keep it and drive it for a week and do whatever he had to get it right only ended up costing me half a tank of diesel and EGR cleaning and a new fuel filter.

[tyberwan]

Hi

did you manage to solve your problem as I have a similar one? The only difference is that after discovering that the pipe going into the EGR valve was split, I repaired it and it started to smoke a lot when in traffic. When I disconnect it, it is normal without any smokes.

However the limp mode is still here when I go over 3500 on the rev counter.

[debjohn]

hi just blank your EGR off at exhaust manifold end and should stop the smoke , i did, been ok since

[tyberwan]

Hi specially to Karl

Don't know if you are still reading this but I had the exact similar problem with my car going into limp mode once I hit 3500 rev particularly if the engine is cold. This happened after I noticed that mt EGR hose was split and I repaired it and put it back.

Then my problems started - car started to go into limp mode and lot of white smoke when stationary. I read a lot on this forum and I did not want to change the EGR valve as this would be costly, so I followed the advice of plugging the valve with a screw. This seemed to have solved all the problems.

I now can push my car beyond 4000 rev and it does not smoke. It seems that the EGR was playing tricks, so I conclude that the valve was stuck with something/soot and everytime it hesitates to work properly, it does not give the appropriate amount of air/gas into the system and the car chokes somehow and goes into limp mode. By bypassing this, there is no air/gas hesitation and the engine does not recognize that there is a fault. It is my amateur theoretical explanation of this.

Now your problem when replacing a new EGR valve, and it still does not work, perhaps that would be somthing beyond the EGR, clogged inlet or something at the source not giving the correct amount of air/gas thus creating a situation for the car to go into limp mode?

Regards

[Trainerman]

Hi I had a similar problem, it tuned out to be dirty diesel and a blocked fuel filter.