Turbo serge

I had a case of low power coming home last night up a hill. Got code P0234. Over boost. I looked around could not find anything wrong cleared the code and tried the hill again. In 1st I red lined the tack no problem. In second it went to 3000rpms then it stated surging 3000 then it went flat then it surged to 3200 then it went flat again then it surged to 3400 then it stayed there so I shifted to 3rd and it went to 3000 and that was it. Shifted to 4th and over the hill. Does anyone have an idea why it would surge like that?

Sounds like the vanes are sticking.

How many miles on the turbo? How hard is this car driven?

I bought the car with 317xxx now has 351xxx. I usually take it up to 3000rpms. If i clear the code it will run good for 100 or so miles the do it again.

Check your turbo actuator and the vanes; if it's sticky or the actuator isn't working right it'll do that.

At this mileage with an OE turbo it wouldn't surprise me if you have enough wear on the mechanism that it's not just dirty, it's worn and won't operate evenly -- which may mean it's turbo replacement time.

If it IS just dirty it can be cleaned.

I checked it with a Mighty Vac. Starts moving around 3 or 4 and stops at 15. Would an OE turbo last this long?

Sure, it well might. There's no way to know, precisely -- much depends on how you use and abuse it. Hot shutdowns can kill a turbo in a very short period of time, for example, while with reasonable use they frequently outlive the engine.

I'd find someone with VCDS and log it while under conditions that like to produce the limp mode. You should be able to figure out if it is under or overboosting when it happens, and from there run it down assuming it looks ok up front.

Do check the vacuum hoses and such, especially if they are original -- they're almost-certainly in terrible shape by now and leaking like crazy.

Most of the hoses are black rubber, maybe silicone, and look fearlly new but I don't know as I got it like that. A couple are cloth like the one going to the actuator but hold vaccumm whar I checked with Mityvac. Acually all are rubber except the one going to the actuator.

I have heard of owners swapping out the vane control ring in their high mileage VNT turbos and having more years of predictable use.
Before I pulled the turbo, I would certainly run VCDS logs and what exactly is happening.
You own a Mighty-Vac, use the vacuum gauge to see how much vacuum your pump is producing--or not producing--as your limp mode may have a very simple fix that does not include removing the turbo.

Check out the stuff in the Ross Tech wiki before you r+r the turbo.

dieselnuts said:

I bought the car with 317xxx now has 351xxx. I usually take it up to 3000rpms. If i clear the code it will run good for 100 or so miles the do it again.

Click to expand...

It's a matter of having a good load such that you're sustaining boost levels for a while.

The code is being triggered not because you've run for 100 miles (or "so"), it's triggered by meeting a certain condition. Sometimes that condition is tricky to duplicate, but IF you for sure are readily getting the code then there is a condition/pattern that one should be able to figure out (nice to know so that you can test against the same conditions following any fix, but really not necessary [if one can do logging]).

Only real way to troubleshoot this, w/o headaches, is using VCDS, logging performance data.

I been running it harder and good so far. 1st gear almost red line, in 2nd I can get it to 3800 rpms, 3rd up to 3400rpms and in 4th I run out of hill to push it. Done this several times and seems to run much better. I got a few hundred miles with no problem.

My next issue to work on is glow plug #3 is throwing a code. What is the best way to remove it with out snapping it off. I have one ALH here with a broken glow plug that I can't get out. Will a 3/8 air impact be a good way to go about it? I mean better then a breaker bar or so?

I sprayed mine with PB Blaster a couple times a day hot and cold going to work for a couple days.
When I was ready I sprayed them again and waited a while.
Work them back & forth and they come out easy.
Someone here may know the toque spec NOT to exceed!!
Been a while since I did the compression check.

Some have said to actually tighten the glow plug if it doesn't want to move when trying to remove/loosen. I have one acting up myself and I need to get my volt-ohmmeter out to find which one is causing the code. I will try the PB Blaster trick, as when I used it on my 100k miles plus injectors when I pulled them they came right out; not needing a slide hammer.

I got the glow plug out.I soaked it with PB Blaster but it did not want to come out at first. So I thought I start it and let it warm up and while it was running I tried it and it gave a little after that a little more and more until it came out.