PCV System/Turbo Issues & some questions - 1995 854 Turb

[ferrari9]

Distinguished members of the board...

It's been some time since I've been around here and situation now dictates my need to seek the collective wisdom of the forum. Anyway, its nice to see matthewsvolvosite acknowledged at FCPgroton.com.

Anywho... I have encountered a slight problem with my 850 recently. While driving home from work a few weeks ago I attempted to pass a slower driver and while putting the pedal to the floor I heard a loud POP under the hood and suddenly had a great loss of power. I would equate the sound to someone "knocking" once with a balled fist from the inside of my engine bay. Other than the power loss, the car seemed to be operating just fine. Before I arrived back home, I stopped off at a local gas station to check out the situation with proper lighting overhead and found that my air-intake hose had disconnected from the "fit-piece" that sits just aft the grill. The hose was the main line running from the grill to the airbox and it was disconnected at both ends. Slightly puzzled, I re-connected the hose and drove on home. Next day, I thoroughly checked the rest of the "importants" in the bay along with DTCs and found nothing out of the ordinary.
Over the next few weeks I dealt with this same problem of beginning a journey with the car operating fine, air-intake intact, while somewhere along the journey I would get the power loss and again check to find the air-intake hose "popped" off. During that period, I would also make sure to check everything else out along with the DTCs and, again, nothing else caught my eye.
I finally had a couple of days free to address the problem properly so I went ahead and picked up a few clamps and some plastic pull-ties and I reinforced the intake from the grill to the box. Took care of that problem, however; driving to work in the wee hours of the mourning this past saturday arose a new problem. As I was getting onto the highway and rpms approached 3-3,500 and the turbo gauge entered the "white zone" the engine started hesitating and black smoke poured from my tailpipe. Since the car was operating just fine below 50mph I was thankfully able to complete my journey with the cruise control on at about 45mph with my hazards on. Later that day I took the back roads home and never went beyond about 40mph and the car drove just fine. In fact, I never got a lambda code and the car idled and operated smooth as a baby's bottom.
Needless to say, I've already scheduled an appointment with my local Volvo service team to correct whatever is going on, and I already have my suspicians as to the culprit, but I wanted to get some second opinions so I can go in there armed with some better information.
So... is anyone else thinking PCV system or vacuum hose issues? or... is my turbocharger possibly on its death bed? any other thoughts?
I was literally just about to order all new turbo and cooling hoses and also just about to replace the PCV system in accordance with completing all of the car's "stage-zero" needs so it really wouldn't surprise me if any of these were to blame. However, if the turbocharger is going on me I have another question: should I replace with another (stock) TD-04 15G or is it easy enough to just slap on a 16T and have it operate at the stock 9.6 psi with slightly more efficiency?

Some important information regarding this issue:
The only two mods I've done to the engine system so far are a K&N filter and a turbologic MBC set to 1psi above stock settings. I know it is pretty irresponsible to run an MBC without completing those last yet very important stage 0 projects and this may or may not affect the situation.

Also some quick questions about my turbocharger since this whole issue has got me thinking a bit:
As far as I know, my 15G turbocharger has a ceiling of around 15-16psi of boost - correct? As far as I can also tell, the 15G is not even efficient beyond about 15psi - correct? I also suspect that running a 16T at stock or slightly higher (10-13psi) will operate more efficiently than the 15G - correct?
The reason I ask is because the car will have a few small mods done in the near future and I am curious if running a 16T will improve every-day reliability under such conditions. If the stock turbo is on its way out, maybe a good idea to just plus1 anyhow since the cost is not much different for the unit itself (according to Volvo).

Thanks for braving my novel and any input would be GREATLY appreciated on the subject.

Nicolas

(Would anyone also be able to point me in the direction of a complete and fully accurate relevent text or texts describing the complete thoery of operation of this engine - aside from the service manual? I have found countless articles online yet all the info is very conflicting and I'd rather educate myself with scientific data rather than approximates from weekend mechanics like myself. )

[Ozark Lee]

As i read from your esteemed posting I gather that the hose that popped off was on the intake air side of the airbox. Other than depriving the intake air temperature sensor of its actual ambient air temperaure that should make little difference in the performance of your vehicle.

Since I am a pauper and my 850 does not have a turbo I am at somewhat of a loss as to the nature of your specific problem. The only thing I can think of is a backfire that would release the hoses from their specified mounting positions. Did you encounter a misfire or or a backfire prior to the premature ejection of your hoses?

At the end of the day I think you will be fine, mighty fine.


...Lee

[robert213]

As I was getting onto the highway and rpms approached 3-3,500 and the turbo gauge entered the "white zone" the engine started hesitating and black smoke poured from my tailpipe.

Black smoke equals running very rich (too much fuel for amount of air ingested).

This occurs when air flow meter (MAF) measures more air than actually reaches the throttle body on the intake manifold. Cause of problem is a massive air leak between turbo, intercooler, and throttle body -- such as a hose which has become disconnected from intercooler.

[ferrari9]

Ozark...
You're right on the money - the hose popped off where the air enters the airbox. I'm glad you've made this point for me because I was pretty sure myself that this would have little consequence other than a tiny loss of power. As a matter of fact (as a funny sidenote) the last time I was at my dealer to order a new hose, it happened that I hadn't had my car with me so I had to go out and look under the hood of a '94 855 turbo that was owned by one of the parts guys. As we popped the engine bay and searched for the part number on the hose I noticed that the entire section of hose from the air box to the grill was missing! It was pretty hilarious because here I am talking to an "expert" in Volvo parts and as I looked at him and said "Had you noticed this hose was missing?", he looked at me like I had three heads and replied "What hose? Is there supposed to be a hose right there?" Um.... yeah! Pretty funny. Anyway - now that you mention it I hadn't noticed a backfire or misfire before the incident and there were no misfire codes logged. Something to look out for in the future, though. I am lucky that its a Volvo - like you said, at the end of the day the car will most likely be mighty fine. Sometimes I swear you could remove the entire engine and it would still get me to where I need to go LOL!! They build these things like M1A1 Abrams! Seriously, though, the stretch of I95N that I take to work four or more days a week isn't much better than driving the baja rally yet it hasn't phased the car one bit.
-also-
Excellent insight Robert - it makes total sense that this would create such a disruption. I'll take a look first thing in the morning and even if my eyes don't catch anything I'll surely mention it to the Volvo techs on Thursday. Since I know that it isn't the grill side of the intercooler for sure, I'm probably having a problem with the other end of the connection. Wouldn't surprise me at all since most of the other hoses I've inspected look older than the sun itself. Do you think it would anything to do with the MAF itself?

Thanks again, guys, for the advice!

Oh, and I forgot to mention a couple of details in my post. Haven't been around in a while and I didn't realize the new rules of posting until now. What I left out: car has 147k and change and since I purchased it about two years ago with 90k miles I've kept up with all regular service intervals plus a general service done by me every week to at least check general mechanicals, fluids, etc. and make adjustments as necessary. Unfortunately, the woman who sold the car to me didn't take very good care of it. She was very late on almost every oil change, tune-ups were scarce and I doubt she ever let the engine block warm up properly before driving or likewise let it idle and quench the turbo before shutting it off. God only knows how else she abused the poor thing but thank the same entity that this was a Volvo because you'd almost never know it now (aside from all the scratches and dents on the 019 black paint - doh!) Well, even though she learned to drive at the Helen Keller School of Traffic Violations she did sell it to me for mowing her lawn all summer that year and besides, she's my gf's mom, so I gotta love her!
Only other info that was required by me was the location info and this car was made for the U.S.A. and owned and maintained - and still resides in - good ole stuck up Connecticut.

[MadeInJapan]

Don't know why your front hose is popping off...I too suspect the MAF (you went to K&N recently right...could have oiled the MAF, you know) and it would be well advised to clean it. Also, look under the throttle cover...you might have burst the funny looking hose that has a finger going to the IAC...hard to see with the cover still on. Anyway, that to me sounds like where the original "pop" could have come from.

[oceanman]

i had the same problems with my 94 855t (211k mi). under the accelerator cable cover there is a hose that runs from the top of the idle air control valve to the vacuum tree. apparently it dry-rotted and had a crack letting air in. when the turbo would kick in the engine would loose power and there was black smoke coming out of the tail pipe. it is an odd shaped hose with two different diameters. i replaced it and everything is fine.

[ferrari9]

MIJ & Oceanman -
Just went out to check this out and unfortunately the hex bolt on the cover is stripped (damnit!). The guys at the dealership have tools to deal with this so I'll have them remove the bolt and cover first tomarrow. If this is the problem it'll save me lots of $$$ in the long run instead of having them trouble shoot everything else. What I should do is epoxy a hex that I don't need to the bolt, remove it and the cover and take care of this myself to make it easier. I lucked out on this one, though, because I've got the good old rents helping out and if this is the problem then it shouldn't cost too much. I know this is a bit irresponsible and a waste of money but as long as it's fixed I'll feel better.
Thank you for the troubleshooting - it sounds pretty unanimous that this is probably the cause (and it wouldn't be the first time MIJ gave me correct advice). I'll make sure to update this post with the actual problem tomarrow when I get home and how everything worked out.
MIJ - it sounds like the board may have another post for the 850 repairs section...

Either way, I'm damn glad to hear that the turbocharger itself probably isn't the culprit.

[MadeInJapan]

Good luck....and let us know. If that isn't it, then we're back to the drawing board. But Turbo's on these usually don't go bad until way beyond 150K miles, and that's usually with some maltreatment.

[ferrari9]

Okay... Back from a long day out. Good news, though: the culprit was indeed the throttle hose (located under the throttle body cover). As you all suspected, it was rotted out and just went in the last month. Actually, MIJ, you were right on the money as the tech informed me that the "knock" I heard was the throttle hose basically blowing up under there. I'm lucky the car ran at all but it's just another testament to how solid these cars really are. I've said it time and time again but it still never surprises me the quality with which they build these cars - even for mine being 12 years old!
The second part of the problem was a minor one - the upper intercooler hose was on its way out as well and so we just went ahead and replaced it.

The overview for the service performed to correct this problem is as follows:
1. Replaced broken throttle body hose
Volvo Part # 9161093-1, $101.96
2. Replaced deteriorating upper intercooler hose
Volvo Part # 9161092-3, $59.04
Total Labor 1.70 hrs: $178.50
(the only other service performed was to add some carboretur cleaner)

To be honest with you guys, the car is driving with new zest that it hasen't had in a while, so I would suggest that if anyone else is driving a turbocharged 850, go ahead and inspect whether or not this needs to be done to your car. I suspect that the two hoses have been on their way out for a while now and I am actually really glad I've gotten this small fix out of the way. It's amazing what a little vacuum pressure can do for an engine!
Just to mention this, too - the engine is not just running fine again but the tranny is shifting smoother and the power is just instantanious. All around a great day for my car!

Just in my opinion, since I've seen at least half a dozen examples of this problem while looking around the net and here on the forum, it may or may not be a good idea to add this post to the repairs section for anyone who may encounter this problem in the future - if there is not already a write-up on it of course. I would also strongly suggest that this service update be suggested for all stage-zero applications since it has proven to make a huge difference on the car's performance. Even if you're not planning to mod the hell out of your 850 (as I've choosen not to - for the most part) it is still always a great investment in the future of your car to have these stage-zero tasks completed. As proof, I've spent the entire summer thus far catching up with stage-zero needs and as a result I had the techs at Volvo telling me that mine was one of the cleanest, smoothest running 850s they've seen in a while down there and that they have no doubts the car will be just fine for many years and miles to come. I learned all about the importance of stage-zero tune-ups right here at the forum from dedicated members such as MIJ, and the advice I took has proven its weight in gold my friends.
I would, however, suggest that if you do need to go ahead and perform this operation on your 850, and you have enough confidence in your mechanic skills, to go ahead and order the parts on your own by referencing the PO#s I listed above and doing the labor yourself - it'll save you about $200 in the long run. Besides, replacing vacuum hose is a very easy project and simply takes a little time, patience and some grease remover for your hands.

Little fixes = huge smiles and lots of miles

Consider this thread officially closed...

Huge thanks again for all your valuable input everyone!