LIMP mode. question

[Ben Dur]

so i experienced limp mode for the first time ever.
restarted the car and attempted to induce it because i wasnt actually sure that it was limp mode, as ive never experienced it before. the second time it limped on me it even threw a MIL.

plugged in my VCDS-light and it was, i forget exactly, "charge air control positive deviation. sub line noted intermittent". or something to that nature.

did some research and diagnosed the problem to either the VNT actuator or the VNT mechanism inside the turbo.

when i apply vacuum to the actuator pod the actuator arm begins to move at about 5 inHg and then freezes about halfway through its range no matter how much vacuum i applied.

i reached down there and gave it a little nudge and it snapped the rest of the way. after working it a few times it now moves all the way but it seems to freeze up about 1/2 way through its range before snapping further on its own. it seems to move all the way through its range between 5-17 inHg of vacuum but it freezes up and pops at about 14inHg before finishing its movement.

i have ordered a new VNT actuator, but id like to know if its the VNT actuator which is freezing up, or if the turbo itself need to be cleaned. (as removing and disassembling the turbo would be a weekend job and requires a few additional gaskets etc)

really just wondering what typically causes this symptom, or if it is not necessarily a giveaway as to whats bad.

thanks in advance for your input =D

 

[DanG144]

You have to make the determination of turbo or actuator after you disconnect them. It will be very obvious which one it is.

Tie a piece of dental floss onto your new circlip before trying to put it on. They fly very, very well, and a 4 inch piece of white dental floss gives you a good handle on it, and a way to find it again.

If you run out of clips, you can use stainless lockwire to hold the actuator onto the lever's shaft.

It sounds as if you know it should be set to start moving at 3-5"hg, and be at full stroke by 20" hg.

 

[oilhammer]

When you take the actuator arm loose, see how the VNT arm on the turbocharger moves by itself. Usually it is NOT the actuator that is sticking, but the turbo vanes themselves.

You may be able to get it apart and clean it, maybe not. If it is your time, and you are willing to spend it, you can certainly try.

If this car came into my shop, and I could not get it freed up from below with some penetrant and some repeated movement of the arm, it would get a new turbocharger. But this is primarily because I cannot charge someone to take a turbo out, apart, and put it back together on an assumption. But if it is your time, it is a different story.

(if it were my own personal car, I'd slap a new turbo on it too, because I would not want the downtime myself).

I may have some used turbos still laying about if you want one to tinker with.

 

[Ben Dur]

what your saying is i should probably just get a vnt 17/22 and call it a day =D

thanks for the input guys

 

[oilhammer]

Haha, well perfect time to upgrade, but as you probably already know you'll need some other bits to go along with that bigger turbo. But I like your way of thinking!

 

[Ben Dur]

it'll happen eventually. and im very much aware that it takes a few bits to make it all jive.

this weekend the new actuator will go on to see if this will remedy the problem. if not a new intake manifold gasket, exhaust gasket, and the oil return line gasket will be on order.

also the vnt actuator seemed to be leaking a bit of vacuum. hard to explain how much. not to badly but it was leaking none the less. i dont know if that changes any diagnosis

 

[DanG144]

It just confirms that you need a new actuator.

 

[Ben Dur]

ok cool. well its on order already so hopefully that will do.
thanks again to both of you.

 

[Ben Dur]

couldnt get the turbo apart but i soaked and flushed it out with a mixture of diesel and WD40 for a couple nights.

the actuator arm was definitely binding up, but after working, soaking, flushing, it now moves freely: so freely it just flops back and forth. the bin i soaked it in had alot of settement at the bottom by the time i was "satisfied."

the old actuator was also kind cruddy and was indeed leaking vacuum. replaced it. everything was then moving smooth.

reinstalled everything and now the car is more responsive than ever before. just got it together last night, so today ill run some logs to make sure its not overboosting.

Thanks for the help guys

i need to plug IDparts.com as i ordered the actuator etc on monday at noon and on wednesday the parts were at my doorstep, thats with free shipping too. complete with a spare C clip. these guys must have shipped the part within hours of my order!