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Discussion Starter #1
Heres a quick rundown/history of the car.

Its a 2005, BEW. 149 xxx KM on it. It had a failing turbo/limp mode problem for about a year, I finally decided to do something about it and fix it. A friend of mine who is a mechanic had a similar problem with a VW that came into his shop, he did a Tbelt/waterpump, headgasket, and replaced the turbo assembly as well as cleaned the intake/intercooler etc.

We did a timing belt/waterpump on my 2005, we just simply untensioned the tensioner, slipped the old belt off and slipped the new one on being careful not to move either the crank or cam. We also pulled the intake and cleaned it, it was very very dirty. Also did the oil change, air filter, fuel filter, surpentine belt/tensioner.

Next we pulled the turbo, seperated it and noticed the vanes were very free, and moved fine. There was little carbon build up, however there was VERY excessive shaft play.

We put the car back together, it had more power, but the obvious wear on the turbo was causing a power loss. 3 weeks later the turbo failed, the shaft broke inside the center section somewhere. When this happend there was a very sudden loss in power, the car would only go 30km/h.

We got an updated VW turbo manifold assembly, replaced it and went for a roadtest. The car felt like it was still in limp mode, and all of a sudden I accelerated off a stop sign and the car 'took off' it had more power then I've ever felt in a diesel VW, regardless of throttle it kept accelerating. I hit the brakes hard (in gear), and shut it off around 4500rpm. The car didn't buck at this time, it just felt like the turbo wasn't working (still).

It appear's it sucked in some oil that had collected in the intercooler when the previous turbo failed, I guess it used this oil as some alternative fuel? Anyways. I removed/drained the intercooler and all charge piping and cleaned everything very well.

Now, I take it out for a road test, and it bucks very very very bad. Anything over maybe 10% throttle it almost feels like it hits a low rev limit, but happens earlier in 2nd then 1st. Depends on load it seems.

When I scan it I get a bad o2 in bank 1, (I think when the turbo failed a section of the exhaust wheel broke and took out the tip of the sensor), as well as coolant reading high sensor. The coolant code when away when scanned, it does come back (been around for a couple years), however the o2 won't clear.

The bucking is really horrible, the car is undriveable. It free rev's in neutral just fine, and starts/idles well. The car isn't smoking excessively either.

Im curious what I should check? I don't know where to go from here really. I wish I was getting some more codes when I scanned it so I would know what to look at. I've considered pulling the valvecover and inspecting the wiring on the injectors, and I also wanted to disable the EGR, somehow just keep that flapper shut. I don't care about the CEL. I really just want the car to run properly/reliably.

Also, is there any way to test the wiring going to the wastegate accuator? I read its a common spot for problems, with a visual inspection I don't see anything wrong. Could the timing belt have jumped a tooth during the rapid acceleration? Would being off a bit cause excessively bad bucking?

Any help would be great :) Thanks!
 

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First thing I would do is get the timing lined up properly and check it, it doesn't matter how good you are there's a good chance it could be out because of not using the locking tools. The other thing would be to pull the sensor out and see if your theory about the tip being broken off is correct. Finally maybe there's still some oil in there going through the cylinders, where did you get the turbo from?:)

welcometomyturbodies
 

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The engine ranaway due to the failed turbo oil: http://www.myturbodiesel.com/1000q/stop-runaway-diesel-engine-how-to.htm Good thing you knew to stop it!

Worst case: bent rod due to oil ingestion and hydrolock. I would get VCDS and adjust the timing. Even if the crank-cam don't move much, if you refer to the videos in the FAQ, you'll see it's not possible to tension the belt without them moving. So even if you didn't move it with the belt off it moved when you tensioned it. IMHO, a $40 tool isn't worth not using on something so critical. You can substitute the pin. I even rent the tools along with some other places.

Now that I've scared you :D more likely: the high rpm from the runaway or timing belt job blew an intake piping. The fast clip connectors tend to pop off if the tabs wear down or if BOTH sides aren't fully clicked in. If you can't see any bad hoses, do a boost leak test: http://www.myturbodiesel.com/1000q/multi/boost-leak-tester-DIY-check.htm see the mk4 FAQ for many more useful DIY. To test the VNT smart actuator sensor or check the timing you need VCDS.
 

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Discussion Starter #4
So a little update. After work I decided to take a look under the hood. I noticed I forgot to connect the upper intercooler pipe to the flex pipe that connects to the intake. DOH!! Haha. I connected it and that quickly solved that horrible surging issue.

While I was there, I went over all the vac lines, other intercooler pipes and generally gave the wiring harness a visual check. Everything looked OK.

I scan it, coolant temp high code as well as the 02 sensor code. The usuall, clear them. CEL goes off. However, watching the scanner both codes re-appear quickly.

Take the car for a drive, it revs up fine till about 2100-2200 then takes off, the turbo seems to be coming on very late. It pulls fine to 4000. It seems to work fine, even on the highway gets up to speed no problem, it just feels like a bit of a dog in the lower RPM. Kind of like how it would feel in limp mode, except until the power comes on in the higher RPM.

The turbo assembly came from my dads friends buddys shop who is a VW/Audi specialty place, Its an OEM unit but it seems to be revised, it came with a replacement EGR tube, everything else fit exactly like OEM. Wiring on the wastegate, exhaust, charge piping etc.

Well, I figure I can replace the sensors causing the CEL, do a boost leak test and if its not that expensive I may replace the MAF sensor as well.

Also, as recommended I should re-check the timing belt to make sure everything is bang on, maybe if its a bit retarded it could be causing the power to come on late as well? Im unsure how it would effect performance being out slightly.

I will update this thread with results as things progress.
 
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