2000 V70R light surge at speed

[John850GLT]

Sounds like my problem, sort of. I would appreciate input.

I have a 2000 V70R, 205,000 miles. Sites say it has the 2.3 liter turbo, but that's incorrect: the 2000 came with a 2.43 liter (engine code 60).

At highway speeds (light throttle for 55 or 70) it will intermittently, but consistently, feel like it's engaged in a light and quick stall/surge pattern. Usually subtle but, sometimes, noticeable to passengers. At the same throttle, doing 25/30 steadily, no issue. Only on the highway.

Car still does 0-60 under 8 seconds, no complaints when called upon for any routine use; never a stutter. Starts flawlessly. Idle steady as can be, whether cold or hot, at 900. That makes me think the ETM (grrrr, what was wrong with the mechanical type?) is ok-no cleaning needed, nor electronic strip issue.

I have replaced hoses from purge valve and from exhaust manifold, thinking leaks, and adjusted wastegate slightly. Gave it new Volvo plugs and Bosch ignition coils a year ago. Cleaned MAF.

I believe this issue started after putting a catalytic cleaner additive in the tank to see the effect on a 422 code (no help), or when I reconnected a hose (next paragraph); there is now Seafoam in the tank. I've also switched to 93 octane, although it seemed quite content on 87. Never a code except P0422 (which is always). I don't believe a bad O2 sensor (rear, but on front of cat) would cause an issue, but if anyone has experience with that, I'm willing to learn!

I did find that one of the hoses, running from purge eventually over to the air intake hose just above turbo, had come off at the turbo end; I reconnected, and I believe symptoms started then, but not sure as I did that shortly before Cat Cleaner.

I noticed from the records that the previous owner changed the fuel filter every couple of years; I reckon that if that were the issue I would have symptoms at other speeds and loads.

So, any ideas would be really appreciated as this issue sounds to me like one that a mechanic could take a lot of time to figure out.

If it were a switch of some sort, wouldn't that be either good or bad, and throw a code if bad? Could the turbo have some air leak around it?

Thanks, all.

[erikv11]

... Could the turbo have some air leak around it? ...

That's what I was thinking. It is very common for the 16-year-old CBV diaphragm to have small stress cracks or holes in it. If the CBV has never been serviced, it would be a suspect. Does it give any boost flutter? It doesn't have to if the hole(s) is small, but that is another symptom of a cracked diaphragm. To test it you can see if the CBV holds a vacuum, otherwise you just have to pull the diaphragm and eyeball it, not a pleasant task.

[abscate]

Topic split from thread, renamed for model

[John850GLT]

So, the wastegate is separate from the CBV? The vacuum diagram so indicates, but I'd like to be sure since I didn't mention it.
I'll check the site for DIY info on that, but what I've seen so far says the turbo must be removed to replace it.

[scot850]

I wouldn't run the 2000 V70R on 87 octane, especially when pushing on. It is a sure fire way of burning a valve.

Check the CBV using vacuum as suggested and also the vacuum pipes if they are old/original. On a 19T turbo which your car probably has, you will need to pull the turbo to replace the diaphragm. If you check on the timing belt cover it should give the engine type ID. I suspect it is a B5244T2 as I have in mine. Some say it is a 2.4 others a 2.5 litre engine. Most websites (other than IPD) always get it wrong.

Neil.

[John850GLT]

It is a 2.43, the B5244T2. Engine code 60 (not always listed). Never found a site for buying parts that has it right.
What about the turbo control valve? That's a 10 minute job.
Pulling the turbo-not a DIY job? (I have the street as my garage.). Must cost a bit to have it pulled and the CBV replaced.
Much to learn.....

[abscate]

If it's anything like my T5 the CBV diaphragm was a 9.5/10 b***** of hardness. I wrote a thread on it to whine.

[sleddriver]

At highway speeds (light throttle for 55 or 70) it will intermittently, but consistently, feel like it's engaged in a light and quick stall/surge pattern. Usually subtle but, sometimes, noticeable to passengers. At the same throttle, doing 25/30 steadily, no issue. Only on the highway......I did find that one of the hoses, running from purge eventually over to the air intake hose just above turbo, had come off at the turbo end; I reconnected, and I believe symptoms started then

Engine air intake will be much higher at speed than at 25/30. Further, you mention the removed hose you found. Being off at the turbo intake should have caused a problem as unmetered air was entering the engine. Another source of the problem may be any check-valves. They tend to fail over time, causing problems in our old cars.

To begin and narrow down the problem, I'd smoke the motor, intake and vacuum plumbing systems thoroughly. Build yourself a smoker if you don't already have one. I use incense & firework punks in mine. You'll have to plug the intake and maybe exhaust pipe and maybe gas tank vent to seal everything up. May also have to seal the oil hole in the bottom of the intercooler if there is one. This all needs to pressurize in order for smoke to escape from the leak. This is time well spent as you may find more than a single leak.

[John850GLT]

Thanks to all for the input. Of course when all is done I'll post the disposition.
For now, the problem is getting noticeably worse.
My mechanic looked up the labor price, and his computer said .75 hours for turbo removal. (Abscate, is that a guffaw I hear?) I'll see him again next week when he has time to behold the turbo.
For now, I'm going to creep forward with easy things, new hoses and boost pressure solenoid. Since the solenoid, hoses and diaphragm are under $100 it seems prudent to do that before turbo removal.
Wish this were a DIY job. How I wish I had a heated, well lit garage.

[abscate]

All data says 5.2 hours for turbo replacement. You can spend 45 minutes on one manifold bolt.

Someone read the wrong column...