VW TDI forum, Audi, Porsche, and Chevy Cruze Diesel forum banner

1 - 4 of 4 Posts

·
Premium Member
Joined
·
3 Posts
Discussion Starter #1
Fist off, thanks for the great site. I have literally spent the last 3 hours reading everything from mk3 tdi to current. I must say the diesel info found here is better than pay subscriptions such as alldata or mitchell. Very impressed.

Fist off, i work as a german auto tech. All i own is german cars. It is my profession as well as my passion. With that said, i have never had to really diagnosis a tdi until 3 weeks ago. Prior to this time, my limited interaction w/ tdi's was service items like timing belts or state inspections. This is not because i haven't wanted to, just i never had the chance too. My clientele is not the tdi market nor the diesel market. I have worked on more diesel g-wagons than tdi's. So my interaction w/ vw diesels has been rare. That was until my friend bought a used tdi and my pumpe duse saga begins

2004 bew jetta wagon. 160k on it. My friend asks me to look at it. It has a burned up glow plug harness. I note the glow plugs are different. 1 11v plug and the other 3 were lower rated than what the harness put out. So new glow plugs and harness i think im done. That is until my roadtest.

Upon acceleration car hesitates around 2500/3k. Cross between a compressor surge and detonation feeling. However it clears right up if you down shift it.

This was coupled with a bad maf signal--low or faulty reading. So i watch blocks 10 and 11. I note the maf only reads 700 at wot despite being told it should hit 1000-- turbo works as desired boost is being met. 2000mbar iirc at wot. i chalk up my maf as going bad. My mistake there.


new maf on, no difference. Hmm, did i miss something. So start looking for the obvious stuff. Smoke check the intake tract from the maf tube--no leaks. Pull off the pd diverter valve-- notice a ton of carbon build up. Off comes the intake.

The two piece intake was split apart and soaked over night in safety kleen, hosed off in the morning then put in a blast cabinet and sand blasted to get me back to clean slate. Re clean the manifold to make sure no sand is anywhere then re-assemble the intake and back on the car it goes. Car definitely runs peppier, but i still am bucking at 2500 rpm range.

now i heard form other techs as well as read about the camshaft failures. so while the intake was off, i checked the cam. it is starting to wear out. No lifters are destroyed yet, and each cam lobe still has "shape" to it. but i can run my finger on the edge and feel the knife like edge. so it is on the to do list. But the problem at hand is the bucking at 2500. I dont think a shot cam would do this? if so please speak up.

So i sit here and my work has followed me home. I am brain storming about the car. Then i think back to a week ago when i let the car idle outside for like an hour to warm up and freshen the battery since it had sat before coming to me. I noticed the snow was all black on the ground by the bumper from the exhaust. This was prior to me fixing the glow plug harness or air flow meter. I kinda assumed it was just running rich ala bad maf.

And now i have a eureka moment. What is the chance the egr is dumping to much and effectively killing my a/f mixture. because the maf readings drop during this bucking period. If the egr is opening up through this tme frame, it could be causing a bad a/f mixture--hence the detonation like feeling because im lean and also the lowering of my maf readings. I'm thinking a block off of the egr and road test is in order. Anyone care to shed some light? Does this sound viable or am i talking out my ass?

thanks
Mike
 

·
Registered
Joined
·
159 Posts
Is the EGR the spring type or electric type? It's a common problem for the spring type to not work because of cracked vacuum lines or carbon sticking.
 

·
Registered
Joined
·
482 Posts
I assume there are no codes contributing to the problem? Try a boost leak test using pressure even though you did a smoke test. It's possible something is wrong because you did the smoke test early. Bucking at a certain rpm is normally a vac hose, turbo control, sensor, or major boost leak. It's very possible the EGR is bad. It's an electric type. No way it's the camshaft since you said it's only a little worn. Another possibility is a wire short on the turbo vane sensor, look at the VNT actuator, or as pearlgolf said, bad vacuum lines. Lastly, how's the timing? Check the timing belt index marks and the camshaft sprocket holes. A tiny bump on the cam sprocket can make a noticeable difference. Although it doesn't sound like it, the fuel pressure could be having problems. See if you hear the lift pump in the gas tank running when you turn the key on but before you start the engine or check fuel pressure.
 

·
Premium Member
Joined
·
3 Posts
Discussion Starter #4
with out having my car lap top with me, i dont know the code number off hand. It was a low air flow maf related code.

The code in question has a tsb about it. I will know more monday evening. I wil update my post w/ results what i did to remedy the problem.
 
1 - 4 of 4 Posts
Top