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Discussion Starter · #1 ·
I have 194K on a 2.5. It was running well, but I started getting a rotten egg smell and losing power when going up hills. I assume this to be a failing CAT, but the car wasn't throwing any CELs. About 2 weeks ago, we were returning from an 800 mile trip and experienced a knock going up a grade on a freeway, along with the rotten egg smell. Since this time, the car has been sluggish, but no CEL's. I connected my scanner a few days ago, but no codes appeared.

I also have been losing coolant, about 1/2 cup every 10 days. I was worried about a blown head gasket, but the oil is not milky and the exhaust is not producing white smoke. I think I found the source of the leak; coolant is slowly leaking from the thermostat assembly, possibly through the gaskets.

I connected my scanner again today, this time 2 codes appeared: P0234 (turbo charger overboost) and P0333 (knock sensor 2 circuit high). They are grayed out, IIRC that means the codes appeared, but are no longer active.

So what does this all mean? I don't have any CELs and the car feels sluggish, but does not seem to be in any danger of stalling. The front O2 sensor was replaced at 135K, but the rear O2 is original.

Any guidance would be appreciated.
 

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Rotten egg smell is the cat.


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Discussion Starter · #3 ·
So does a clogged CAT cause the secondary issues of the 2 error codes; like the knocking and turbo overboost
 

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Causes the loss of power up hills etc.


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Over boost can (will) cause knocking, so the codes are likely related. A clogged cat and overboost don't go together, though, on the contrary.

The rotten egg smell is from the converter, not necessarily because it is bad, especially with no codes and especially if it only happens under a high load. Often you can get rid of it by changing brands of fuel, or using a higher octane. The smell can linger for a long time.

So, check the turbo boost control...

[edit] another possibility is that the knock sensor fault allowed the over boost which caused the knock.
[edit2] If the boost senor is setting a fault, you could be loosing boost, hence the loss of power on hills.
 

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When it has the power loss, is it severe or just feels like its pulling timing. The overboost that caused the knock would also cause the ECM to pull timing which would feel like a loss of power. True that some fuels contain more sulfur compounds than others which can build up in the cat and be more noticeable when the cat gets hot enough to burn some of it off. ie. driving miss daisy most of the time but then hammering it can also cause this phenomenon of rotten egg smell.

Overboost look to tcv.


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Discussion Starter · #7 ·
When it has the power loss, is it severe or just feels like its pulling timing.
Not exactly sure what it means to lose power from pulling timing. When the knock occurred, we were climbing a short grade but probably about 2000 ft in elevation change over a 2-3 mile road. We were cruising at around 65 half way up when I found myself needing to apply more pedal to continue the same speed. Car was struggling to maintain speed and it was close to having the pedal completely down. It was at this point the knock occured, as soon as I released the throttle, knocking stopped. It has not knocked since, but I haven't gotten up any steep grades since.

As for the smell, I'm somewhat certain gas played a role, but I'm fairly certain I used Premium. I'm really hoping its not the CAT, as I am in California and the muffler shops I've gone to have not found a suitable aftermarket CAT. Both shops have referred me back to Volvo. $2K for a CAT is over half of bluebook.

Thanks everyone for the input on the TCV and clearing up if the codes were related to the potential CAT issues.
 

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Yes yes. Like others are saying, the TCV might not trigger a code, but it wears out. Some S60 owners have seen it wear by 60k miles. I did one in an XC90 2.5t at around 105k miles on the clock and boy did it make a difference in power delivery and clean running. It took all of 3 minutes to change it as it is easily accessible hanging on the air filter box. There is (fuel/timing) compensation going on when the TCV is not operating efficiently, but since it is mostly within adaptation parameters, it doesn't throw the code.

Use a quality part like the Pierbug and it is fairly cheap at ~$29 at FCP. This part should be on the 100k mile maintenance list for 2.5t owners. This part can help improve lost mpg since the boost and fuel/timing will be correct, but usually, with the excitement in recouped power, the lead foot nullifies that. ;)
 

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Ignition timing, boost pressure and fuel delivery rate all play a role in knock prevention. If one parameter (boost pressure?) is not properly regulated, the engine will knock and the codes follow. The knock can be reduced/eliminated by reducing the boost, "pulling timing" (reducing spark advance) or increasing the fuel rate. Or, as in your case, backing off on the throttle.

A clogged converter would not come and go; it would be present all the time. I hate excessive use of TLAs but I'm guessing Chitown is talking about the Turbo Control Valve, a likely suspect in your situation. Sounds like it's a common point of failure.
 

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No idea if TCV plays a part in this but I replaced mine a couple years ago- https://forums.swedespeed.com/showthread.php?431257-TCV-Replacement-2-5T

Just another reference, cannot say it "fixed" anything outright but did make the engine feel a little more responsive. Still need to rebuild the turbo one of these days, I believe it's a contributor to my oil consumption.
 

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Ignition timing, boost pressure, and fuel delivery rate all play a role in knock prevention. If one parameter (boost pressure?) is not properly regulated, the engine will knock and the codes follow. The knock can be reduced/eliminated by reducing the boost, "pulling timing" (reducing spark advance) or increasing the fuel rate. Or, as in your case, backing off on the throttle.

A clogged converter would not come and go; it would be present all the time. I hate excessive use of TLAs but I'm guessing Chitown is talking about the Turbo Control Valve, a likely suspect in your situation. Sounds like it's a common point of failure.
What John C is saying.

In addition to the Turbo Control Valve (TCV) wear, the valve can stick. This is a possibility of the overboost code where the TCV may have been the cause of not opening the wastegate to bleed boost when it was supposed to. If your lost power and improper running is more than one component, it is still a good idea to change the cheap TCV.

I may have forgotten from other threads, but when was the last time you changed the known troublesome coils? Old coils can run fine under light to normal load, but can also contribute to a misfire or poor running when a strong spark is needed under load or boost. And what spark plugs are you running?
 

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Discussion Starter · #12 ·
it is still a good idea to change the cheap TCV.

I may have forgotten from other threads, but when was the last time you changed the known troublesome coils? Old coils can run fine under light to normal load, but can also contribute to a misfire or poor running when a strong spark is needed under load or boost. And what spark plugs are you running?
I just ordered a Piersburg TCV, should have it tomorrow. Based on what I've read about the TCV, I hope to see a decent increase in power and better mpg. I did try to clear the code on my scanner, but it just reappeared when I restarted the car. I'm using the Torque app with a bluetooth ODB2 dongle. I noticed there is a turbo display available on the app. I enabled it, but there' no reading. Does anyone know if this app or ECU can show the turbo readings?

As for the coils, I'm still running the original coils....lol. The plugs were just replaced last month with NGKs.
 

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I just ordered a Piersburg TCV, should have it tomorrow. Based on what I've read about the TCV, I hope to see a decent increase in power and better mpg. I did try to clear the code on my scanner, but it just reappeared when I restarted the car. I'm using the Torque app with a bluetooth ODB2 dongle. I noticed there is a turbo display available on the app. I enabled it, but there' no reading. Does anyone know if this app or ECU can show the turbo readings?

As for the coils, I'm still running the original coils....lol. The plugs were just replaced last month with NGKs.
It might be time to change those coils too. Very well documented on those issues, I have changed them on a 2.5t and before the new coils, the XC90 could hardly go over 70mph with the gas pedal 3/4 of the way down. Now with both the coils and TCV, when the pedal is barely touched it will accelerate well over 75mph.

Many many people change the 2.5t coils around 100k-130k miles as a normal (and/or preventative) maintenance item. Change all five, don't try to troubleshoot for a bad coil at your mileage. I also like to use the Genuine Volvo plugs when changing these components to ensure a good baseline of the engine performance and to ensure any other issues that may still be present are not caused by the choice of plugs.

Minus a PCV (or related hose) issue and the fuel pressure sensor (which can throw a code), the ignition spark and TCV are at the top of the list for poor running 2.5t which does not throw a code. These parts don't break, they just wear out.
 

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+1 on coil packs, if one fails you really should replace them all- https://forums.swedespeed.com/showt...ith-the-2-5-turbo-on-the-way-home-last-night-!! I replaced with Bosch 0221604008, little cheaper than OE but same manufacturer. I'm guessing they wear out before failing outright (DD noted the issue after failure).

While not asked, I have no comment on non OE for plugs. Figure given how long they stay in, you save a couple bucks a year to wonder the next time you have an issue if it's plugs. Probably need to add them to your troubleshooting list...

I'm pretty much in alignment with the last post, out of curiosity when was the PCV serviced?
 

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Discussion Starter · #15 ·
out of curiosity when was the PCV serviced?
The PCV hasn't been serviced. It was on the list of things to do, but we are actually looking at a new XC90, so this car may just be used for local runs around town. My mechanic had the car a couple of months and suggested the service, but said it could wait, as it drove well.

As for coils, I'm usually proactive about changing stuff like that before they die, but this car has been very good to us and it didn't seem necessary. Though I usually changed my plugs every 30-40K. Everytime I pulled the plugs, they were always really clean and could have been used again for a longer period.
 

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Discussion Starter · #16 ·
Thank you Amazon, got the TCV at 10AM. Once I figured out how to remove the clip holding the electrical connector, got it installed in 5 minutes. Also installed a new fuel filter as that had 50K on it.

The scanner codes cleared immediately once the TCV was installed. Took it on a quick test drive around city streets and had a couple of observations and have a few questions:

1. The turbo seems noticeably louder. I noticed a 2 stage noise. The first is the turbo spooling (kind of whistling noise); I was familiar with that sound. The second came shortly after that during accceleration. The pitch of the sound was different, but I don't remember if it was higher or lower.

2. Throttle response did seem smoother.

As for my questions: Does the ECU need to relearn? I didn't take it on the freeway because the car stumbled a few times during the first mile on acceleration and I was unfamiliar with the second turbo noise. With that unfamiliar turbo noise, could I have been driving with a poorly functioning turbo for a long time and not have known it?
 

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Discussion Starter · #17 · (Edited)
Well bummer, the codes came back. But this time, they can be cleared. When I tried to clear them prior to the install of the TCV, the codes wouldn't clear.

I watched the IPD video on Boost 101/102. So if I am understanding the turbo properly, it seems either the boost sensor is faulty or the waste gate is not set properly; or both.
 

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What codes came back? Have you done the rubber glove test over the filler cap to check the PCV?

The engine does need to relearn since your adaptations were probably way off the median. If you are getting more complete boost, then the coils can have a harder time producing enough spark.

As far as the wastegate, a stock type of diaphragm (non-HD) will suffice if you don't plan to install a performance tune. It is another cheap part to replace, but access makes it a longer job. Vacuum checking if the diaphragm of the wastegate is not torn is a good idea if you can do it. Resetting the wastegate should only be done after you change a part or if you know what you are doing. Other times to reset the wastegate is if there is bearing/sleeve wear on the wastegate lever or another known issue that affects the wastegate arm. Otherwise, leave this alone and it should be a concern further down the road as you tackle other known maintenance.

I would still do the coils first, check for any leaking hoses connected to the PCV, and PCV vacuum operation.
 

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Discussion Starter · #19 ·
What codes came back? Have you done the rubber glove test over the filler cap to check the PCV?
Codes are the same as noted earlier....P0234 and P0333. As I mentioned, I was able to clear the codes after installing the new TCV, previously it wouldn't clear. When I went on my second test drive today, I drove it harder and I think thats when the codes reappeared, but again, I am able to clear it.

No, have not done a PCV test.
 

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Re-read this post and a few things come to mind:

-Check all the vacuum hoses (including TCV and turbo) and validate the intake path from air filter to throttle body for integrity. Make sure everything is tight and connected properly, including the oil cap.

-VIDA is going to be your friend here, preferably with a DICE (or any other Volvo specific code reading tool) but easiest first step is to get a 2014D copy in the OBD forum here on SwedeSpeed and get it loaded on any machine that the VIDA forum suggests will work. Follow the instructions, the process takes some patience but if you can get it running you'll have the best single resource available to rely on as you do more looking for information to resolve this issue. At the age of your vehicle, if you’re really going to keep it you’ll want a copy of VIDA over the long haul.

-Expand your searches to include the other 5 cylinders (S40,V50,X/V70,S80) and see if someone else has had this same scenario. Could even widen your search to include other Volvo centric sites.


The P-Codes you report need converted to Volvo module codes, ECM in this case. There's a converter document in the R forum and if it’s correct your codes go like this (straight from a VIDA copy just like I'm noting above):

P234 = ECM-601C Turbocharger (TC) control system, boost pressure fault. Signal too high, B5254T2
Sources include the valve connections and hoses, air leak or block, or a failing/failed BPC (boost pressure control) valve. Substitute value- Reduced throttle angle and poor performance

P333 = ECM-304C Rear knock sensor (KS). Signal too high, B5254T2
This code suggests the rear knock sensor is broken or loose or the engine is making legitimately too much noise. For this specific code, vehicle ran crappy because that’s what it was designed to do (retard ignition advance) when the code popped up. Can read that in VIDA too.
There’s a bunch more information about troubleshooting, I don't feel comfortable quoting out of their software but there's additional detail on the fault and symptoms and substitute values and the like.

I have a 5 cylinder so I’m always interested in what happens with them and a clogged PCV could be a contributor your problem (direct or indirect), especially if you don't know history. Glove test is a good indicator if it’s really bad. Do the test at both idle and at 1500 or so, needs to suck both times, not blow. Rather than cross post to another site, pop over to FCP and see their PCV write-ups, it's possible that some of the issues you suggest fall into their list of symptoms.

I would not throw anything off the table outright (coil packs, etc.) but I might lean in the direction of something not flowing properly (air/vacuum/oil) as the primary condition that triggered these codes. Vehicle leak from the front or back at all for oil?

Last but not least, I have a small curiosity- at some pop the hood and tell me if the hose that drops down from between the intake manifold channels (runs under the cover near the oil cap and down to the oil trap). Is it made of rubber or nylon?
 
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