2002...running rough and bucking at low rpm! Help please!

Alright I have a 2002 tdi with 209000 miles...one morning I started it wanted to keep dieing on me..ran rough going up and down in rpms! I let it warm up for a bit it kind of cleared up but when taking off in gear in low rpms the thing bucks and surges like crazy!

I am a diesel mechanic so I hooked my scan tool to it P0402 excessive egr flow detected...so I looked into.

I unhooked the vacumn line on top of the egr valve and now it idles and runs fine.....so what is the problem?

Can I leave it un hooked?

I'm a new by on diesel, but on Toyota I ran into a similar problem on a 91 MR 2 5SFE and it was that sooth had clogged valve holes, so vac was not proper. Cleaned everything up, and end of problem. Hope this helps.


Sent from my AT100 using Tapatalk 2

Clean the EGR valve line.

I left my egr unhooked when I had this same problem. My valve is sticking but yours could be your n18 or valve sticking. Another problem I had was my MAF was bad. Egr flow is calculated off a deviation in the MAF reading spa bad MAF can give p0402.

I will clean the egr valve line tonight!

I am also hooking up a better scan tool to read the maf and everything else.

I still don't get how it runs better just by unhooking the vacumn line off of the egr valve!

Switched out egr valves...nothing cleaned out all the oil that was in the intercooler..still didnt help anything. It runs great when i unhook the vacumn line off of the egr valve though!

After all of that we found out that the VNT actuator is all the way down and will not move freeley. Which the turbo vanes are stuck closed and flowing to much egr. Which would make the car run bad cause its going into derate

does that sound right?
whats a good way to get those vanes unstuck?