Diesel guys: Blue smoke under light load?

NYSpeed Automotive
1

So I’m trying to figure this out, car is a 2002 VW TDi, drive by wire, direct injection diesel (injection pump style, no common rail). Under very light load conditions i’ll get blue smoke(always around 2000revs), and a fair amount upon start-up, which lightens up once the car is warmed up a bit.

Basically, what does blue smoke on a diesel mean?

A few things i’ve come across on the tdiclub forum:
-Blue smoke= unatomized fuel
-Blue smoke= timing issue (startup injection out tolerence)
-Blue smoke= bent rods, cracked pistons, hence the motor not being able to fully cumbust the air/fuel mixture?

I thought the injection pump may have failboated, but a code would show up (“fuel metering fault A cam rotor injector”). No code.

Any thoughts? I gotta check compression and some other bullshit to rule the motor out, but i think the #3 and #4 rods are bent…possibly?

2

Are you burning motor oil?

Unburned fuel is almost always the most black smoke you’ve ever seen. The rest of the scenarios you listed would all lead to unburned fuel.

Check your oil… smell it.

3

The oil has smelled like diesel fuel since the car has had 32miles on it when I purchased it new.

4
  • a lot.

Blue smoke means oil.

On the off chance you’re not burning oil, get your injectors cleaned…crappy spray patterns could cause odd problems like that.

5

also check the turbo, if your seals are going you may have oil threw out the intake, causing blue smoke under boost and start up.

6

Thats not normal.

7

well, normal or not, that’s how it’s been since I purchased the car, brand new with 32miles on it. I guess I could have been driving around for the last 7 years with bad rings from the factory. It is a vw, I wouldn’t put it past that pos company ( I have really grown to absolutly hate the car over the years).

As far as the turbo, we will see. I have a brand new vnt17 coming from KermaTDi.com tomarrow, so I’ll see if that makes a difference.

8

Yep, these nozzles do wear out(don’t know what the life span is, these nozzles have been in for about 75k), and from what I hear, fuel not atomizing right will give you the blue smoke bullshit.

9

My TDI was like this too

10

My WRX did similar things when the turbo was going… Oil was leaking out of the seals when there was no load and burning in the hot side/downpipe.

11

Same here - my oil always smelled like Diesel.

12

pull your intercooler pipe off and see if you get 3 qts of oil to dump in your face. seriously. Oil may just be making it’s way through the intake tract. Also check for broooooost leaks. lazy brown

13

No leaking of broooooost, still gotta put new turbo in, see what happens.

14

Ok, I guess I mis-spoke. It is normal:uhh:

You guys know how bad it is to have fuel in your oil right?
Does this not apply to all vehicles? ESPECIALLY diesels?

15

Changed turbo, things improved alot, still some blue smoke here and there, compression test tomarrow.

16

Stock swap?

17

Did you check the intercooler by chance as Carnut mentioned?

18

diesel fuel in oil is prob one of the worst things i can think of.

19

How’d I skip over that, oops…that’s almost as bad as coolant.

20

i still gotta get a compression test done, and see what that yeilds. As far as the oil smelling like fuel, like i said, it always has, since the car was brand fucking new.

I thought it was weird too, the day i took delivery of the car, the first thing i did when i got home was pull the dipstick and check the oil (i don’t know why? the fucking car had like 40miles on it at that point?, but i did) the oil was black as hell and smelled like diesel, not a strong smell of diesel, but you could smell it.

Its been like that for entire time i owned it.