1997 Volvo 850 T-5 with vacuum leak, ODB2 codes.

[DigiHound]

I've got a question regarding a 1997 Volvo T-5 that I'm hoping someone can help me answer. My car has been throwing an ODB2 engine code for several months. the code, P0133, indicates a bad oxygen sensor -- and replacing the O2 sensor did dramatically improve fuel economy. But the code didn't turn *off.*

I took it to a shop and they replaced my new O2 sensor with a different one, but it made no difference. They then put the car through a smoke test and told me there was a large vacuum leak at the turbo.

I have two questions:

1). I have heard that this problem can be fixed by installing a cover made by Mitsubishi and that the affected part is only necessary if you have a manual (I have an automatic).

2). Would a vacuum leak in the *turbo* produce an O2 sensor code? The car continues to run well despite the CEL (the new O2 sensor appears to work properly). The AC unit has some odd behavior, but that's the only problem.

Any advice appreciated. I need to get the car through New York State's emission control, which means that CEL needs to be off.

[RussB]

Exhaust leaks will cause O2 codes, I reckon vacuum leaks would do the same as they let unmetered air into the engine

[DigiHound]

Ahah. Ok. Do you know anything about this supposed Turbo cover that you can get from Mitsubishi?

[misha]

I read somewhere that all turbos for these cars are made by Mitsubishi.

[tryingbe]

I took it to a shop and they replaced my new O2 sensor with a different one, but it made no difference. They then put the car through a smoke test and told me there was a large vacuum leak at the turbo.

Post a picture of what is leaking?

Vacuum leak is different than exhaust leak.

Check engine does does NOT tell you what to replace, it tells you where to look and diagnosis. Blindly replace parts without proper diagnosing is called "throwing parts at it", most of the, it won't solve the issue.

Has the code been reset and came back since the new oxygen sensors?

[DigiHound]

"Post a picture of what is leaking?"

I can't, I wasn't told. The shop (which is highly recommended) told me that they did a smoke test.

Let me give you a little more backstory:

The car was initially showing two codes -- P0133 (slow O2) and P0420 (Catalytic Converter below efficiency). I replaced the O2 sensor and the car's mileage increased from ~18 mpg on the highway to ~23-25 mpg. The check engine light remained on.

I had the light reset when I took the car in to replace an engine mount. It popped on about 80 miles later. This is when I took it to the shop that ended up doing a smoke test.

According to that shop, the car hasn't actually run a check on the catalytic converter, because the low O2 efficiency code is apparently preventing the vehicle from doing so. They swapped out my new O2 sensor with a different part, in case that was the problem, but the car continued returning a P0133 with *their* sensor.

At that point, they did a smoke test, and told me that the turbo appeared to have a substantial vacuum leak. I talked to my Dad, who owned the car before me, and he told me that there was a component I could buy from Mitsubishi that would fit over the turbo and prevent the vacuum leak. Apparently there's a component in the turbo that's meant to work with a manual engine to ensure you don't damage the turbo when the engine RPMs drop suddenly while shifting (apologies if I'm mangling the explanation). In any event, my car is an automatic, not a manual.

The part is supposedly cheap, but the labor isn't -- and I dont' want to pay for the full job if the P0133 code can't be caused by a problem like this in the first place.

[Sommerfeldt]

Apparently there's a component in the turbo that's meant to work with a manual engine to ensure you don't damage the turbo when the engine RPMs drop suddenly while shifting ...

... a wastegate...? All turbos have that...

Seems to me like a vacuum leak at the turbo would mean the turbo's cracked... also, outside the engine, vacuum is carried in hoses and pipes. So those can (and will) leak. I've never heard of, nor can I seem to find, this cover you're talking about - I'm guessing it might be something like a turbo blanket? How that would help a vacuum leak, I've no idea.

I think you should do your own leak testing, and simply start by finding that leak yourself. At the very, VERY least, have that shop point, explain and lay out the problem properly. "A vacuum leak at the turbo" just doesn't cut it.

- S

[DigiHound]

Sommerfeldt,

I have neither the tools nor the skill necessary to troubleshoot the problem independently, and I live in an apartment complex that is notorious for cracking down on people who try to do car work. I've seen them threaten to tow people for changing a tire (no joke).

From researching, I *think* it might be a blow-off valve cover. I got a few other clues that point in this direction -- the mechanic talked about a triangular piece of metal with three attach points (which a blow-off cover resembles) and I was told this is a part that's only necessary if you have a manual. BOVs don't seem to be required for automatics.

Could this be the required part?

[mika]

To answer your last question, no. Re read some of the answers above if you can.

You should be able to look under your hood in your apt complex without problems. Not like you are laying your tools out. Only tool ya need is your eyes to take a look at the turbo (behind the engine by the exhaust manifold) (better view of turbo area I assume would be from underneath, which does not sound possible with your apartment situation) . Try to get familiar with things one step at a time, only way you will be able to maintain this vehicle. I am not competent with turbos by any means, but I think all turbos have an oil supply line, a water line (coolant), and a vacuum(air) connector. The turbo essentially connects the exhaust power back into the intake<sic>, hence "forced induction," kindof like a human on a ventilator.

If you need car to pass emissions, get the code cleared right before you head over for the inspection.

[DigiHound]

Mika,

I can certainly try to look and see if I see any rotten hoses or obvious leak points. Unfortunately, clearing the code isn't enough for NYS inspections. They'll check to see if the car has completed its full diagnostic tests, and they won't pass it until it does.