Another Case of Poor Performance and Smoke

I have read whatever I can find relating to my car's problems and tried suggested remedies without much improvement. By the way, this is my first diesel.

My '03 Jetta tdi started hesitating - or maybe more accurately stumbling -on acceleration and it lacked power. I replaced the MAF with no improvement. I took it to a shop and they replaced the fuel filter (because of some apparently bad fuel) which got rid of the "hitches" but the power wasn't what it should be. I have a Foxwell scanner (which I bought to set the fuel deliver amount after replacing the injection pump cover seal) and the only code was an intermittent issue with the EGR system.

I removed the EGR valve and found it was stuck closed. A good cleaning got it moving again and the code has not returned. But power is still below what it should be.

Somewhere in all this the car had started pouring out black smoke - which appears to be from overfueling. I can't say exactly when because I didn't realize it was happening because it wasn't noticeable in the mirror for a while. The black spot on the ground under the tailpipe caused me to start paying attention.

Next, I replaced all the vacuum lines. No improvement. Then I looked at the vacuum check valve (between N18 & reservoir) and it was working as it should. When I put it back in the car though I put it in backwards and, curiously to me, the black clouds were gone but so was the boost. I put it in correctly and the boost returned... and so did the smoke.
It might help to know that I replaced the turbo and cleaned the intake manifold less than 10k miles ago and it ran well until recently.

Unfortunately I don't have enough experience to know what the Foxwell scanner readings mean. I know the MAF specified and actual numbers improved with the clean EGR and the specified and actual boost approximate one another. But I don't know what the N75 & 18 solenoid readings should be telling me or what other readings I should be looking at.


I'd appreciate any wisdom or suggestions anyone is inclined to share.

Thanks.
Paul

How many miles are on the vehicle? Could be worn out injector nozzles, which would cause excess smoke and loss of power.

Also, when you replaced the turbo, was it new? Used? Rebuilt?

When you had the intake off, did you clean the intake and exhaust ports?

Have you tried running a Diesel Purge treatment through the injection pump yet?

Have you measured how much vacuum your vacuum pump is producing at idle?

Just to start us off

Check the intercooler pipes to the turbo and up to the intake, a loose hose will cause black smoke. Be especially mindful of the hoses behind the passanger side front tire.

Answering the various questions:


-The car has 215k miles.
-The turbo was a new Garrett.
-Intake manifold was cleaned back to the metal, having had only about a half inch opening. Ports were not cleaned but were not obstructed.
-I've put Diesel Kleen in the new tank of fuel.
-Vacuum gauge crapped out so I will get one to check the pump.
-I'll check intercooler hoses.

Thanks for replies.
I'll post an update when I check hoses and vacuum.
Paul

I believe I have found the problem!

Shortly after I bought the car years ago I found that the upper intercooler pipe had been damaged by contact with a serpentine belt pulley - for the steering pump I believe - and a hole had opened. I patched the hole with JB Weld after which the car ran well. And over the years I forgot about it. In looking at the pipes this morning (110,000 miles later) I found that the patch had failed and the hole was open again.

So, after a little grinding I recovered the hole with epoxy, this time with a small piece of fiberglass cloth over that with more epoxy over that - hoping for a more tenacious patch.

TaaDaaa. The smoke is gone and the car seems to be running as it should.

Thanks again for taking the time to help. Eventually, with help from this forum, I might figure this car out.

Paul

Awesome always glad to hear another resolution. Happy trails

Good news! Drive more, enjoy the drive.

Paul in Beaufort said:

I found that the upper intercooler pipe had been damaged by contact with a serpentine belt pulley - for the steering pump I believe - and a hole had opened.

Click to expand...

Glad you found it.
I had the same thing.
During my 1st timing belt change I didn't have the boost hose clamped correctly and when I went for a test drive the hose popped off and hit the pulley.
Did have a small crack which I used epoxy to fix.
Lasted several years and I did have to fix it a few years back.
I didn't have a performance issue but did notice the crack was there.
Grind a bit & more epoxy fixed it again.