Intercooler/vac tree/IAC hose blowing off under WOT
 

Hey guys, the WanderWagen developed a new issue recently and I'm a bit stumped on this one:

So about a month ago I took the car on a road trip to moms and as I was nearing the house I decided to open her up to WOT and get the turbo spinning to blow out any carbon/coking. Upon pulling into moms, it was stumbling, rough idling and generally just acting like a turd on wheels.

Next morning I went out and tried to start it up, would fire up then die. Heard a major vacuum leak and discovered the IAC hose blew off the vacuum tree. Reconnected it, cleared codes, and all was fine. Until this weekend.

Fast forward to Thursday night (7/21): Stopped to fill up the tank, pulled out of gas station, and my factory boost gauge wasn't reading/cut out after I got into boost pulling out of the station. Odd I thought, and figured I must have bumped the vacuum line under the dash loose. Reached down and wiggled it around, no luck. So I drove it and figured I'd look into it when I stopped for fuel again. Opened the hood and found that the screw holding the black cover down over the IAC/vacuum tree was missing, cover still laying in place. Pulled the cover and sure enough there was a vacuum elbow disconnected (which was the one to the gauge). Reconnected, all was fine.

Friday morning comes around: Went to pick up a new tire and as I was pulling out of a particularly dangerous 4 way stop I got into boost (about 3/4 of the way in the white). Next thing I know after the 2-3 shift I'm not making boost anymore and I can hear a major air leak from under the hood. The mid intercooler hose blew off the pipe. Pulled into gas station, reconnected it and torqued down the hose clamp, and off we go with no problems again.

Friday afternoon, as I was pulling out into traffic on US22 in bumper to bumper traffic in a construction zone, I got into WOT again and about 90% of the boost gauge. Low and behold, about 1/2 mile later the car dies on me, lights up all the dash lights as I'm coming downhill. Throw the 4 ways on, pull off at next exit, throw it into neutral and try restarting it. Won't start, losing vacuum in the brakes (almost standing on it to slow down) and finally after 3 attempts she fires back up, albeit with a nasty idle surge and anything less than 1/2 throttle she wants to choke and die out. Pulled into parking lot, popped hood, and there's the problem. She blew the idle air hose valve hose off again at the vacuum tree! son-of-a-%$#@!

Reconnected hose, she's running fine. Take her to get tire installed...

Now, after all of that I'm starting to smell burning oil.

What I'm wondering is this: What would be causing this? It almost seems to me that its spiking boost pressure or overboosting. My first thoughts are stuck wastegate or bad CBV/vacuum lines. Its only doing it under WOT heavy boost conditions. The rest of the time the car runs fine.

My second thought is the PCV system is clogged and pushing too much pressure back into the intake system. However the PCV system was completely rebuilt within the last 3 years/15k miles. I have a new kit that came with the car that I've been holding off on putting in. I don't really have the telltale signs that it needs replaced per se (there is a couple small puffs of smoke coming out the dipstick tube/valve cover once the car is hot occasionally). Its on my list of things to do, along with the 3/8" copper tubing mod I've seen on the forum that is supposed to eliminate the smoking after PCV system replacement issue that seems common...

Does anyone have any suggestions where I can start looking? Could this be an indication of a failed TCV also?

I would think that I wouldn't have too much issue considering its running a factory rebuilt 16T for the last 25k miles and the BSR stage 3 tune with no other supporting mods to really up the boost pressure...So I suspect its only around 18 psi max under full boost/WOT...Any ideas?

Thanks!

Replace the hose clamp

Dumb question im sure but is there supposed to be a hose clamp on the vacuum tree side of the iac hose? When i bought the car/replace the hose there wasnt one on there...

The more i think about this problem and when its happening most often, the more i am leaning towards it being related to the wastegate or cbv...it seems like it really does it when under wot and i lift off the throttle...which would lead me to think that the wastegate isnt operating properly. I do hear a vacuum leak coming from the area of the turbo under normal driving, small but there...so it also makes me wonder if the o ring in the cbv is shot or the line running to it has a hole.

I may look at installing a recirc bov and cbv block off plate in the near future and run new silicone lines. Has anyone had any luck with the HKS ssqv or turbosmart bov's on the 850?

Test your car for positive crank case pressure. my 850T blew off a stub cap on the vacuum tree a couple times. replaced and didn't pay any attention... Next, when I pulled the cover to do the timing belt, I found I had a leaky cam seal. Soon enough I found oil on top of the head, did a rubber glove test and realized the root cause was a clogged PCV. I'm thinking they are all related so I did the PCV and did the cam seal with the timing belt job.

Let me google that for you.

Attachment 14935
http://www.matthewsvolvosite.com/for...3007&mode=view

There is no way that blowby can increase turbo discharge pressure. The turbo already has all the air on earth available to it, and it's electronically controlled as well.

The hoses are probably oily, and that doesn't help. If the pressure is not high you'll have to improve the fit of all those components that are blowing apart. If it is overboosted you'll have to fix that. Therefore, a simple pressure measurement would really help you make s decision.

Thats kinda what I was thinking...I really do need to get a numbered boost gauge installed soon to see what exactly is going on.

I'll grab a hose clamp and put it on the vacuum tree side of the IAC hose and that should fix that. The mid intercooler pipe could have been a bit loose/not seated correctly in the silicone hose...As for the gauge line, I do need to get a vacuum hose elbow kit and go over all the elbows in the system...may opt just to buy some appropriately sized ID silicone or rubber hose and make my own...

PCV system is on my list too I suppose, just for peace of mind (and to get the parts out of my spare tire well).

In my research on the wastegate/cbv theory I managed to stumble across a thread at VolvoSpeed about using the 19T wastegate on the 16T. Has anyone here had any experience or luck using it with a recirc BOV or piston style CBV? Really leaning towards the HKS SSQV or an adjustable Tial/Turbosmart bov...seems like it would suit my needs better than a cbv, and lets face it, who doesn't love the fancy "whoosh" noise they make when the dump to atmosphere :rolleyes:

Given that there aren't really any supporting mods made to the 16T and BSR stage 3 ECU swap that came with the car, I'm still wondering if that may be causing some of my issues as well...Just wish I could get a straight answer as to what the BSR ecu actually does/changes from the stock programming...Unfortunately no answers come from BSR and no one on the forum seems to know...