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New SNAFU: Not getting full boost
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Chaos  



Joined: 07 Nov 2005
Posts: 289
Location: Newark, DE, US

PostPosted: Sat May 11, 2013 11:15 pm    Post subject: New SNAFU: Not getting full boost Reply with quote

Hey guys, need to get some input on a situation that literally just occurred.

I was on my way in to work this morning and in a little bit of a hurry, so I rounded a corner, downshifted, and began to accelerate heavily down a straightaway when I rather spontaneously lost power. Thought I got hit by a fuel cutoff at first (I've gotten a few occasional cuts out of the blue like that lately), but instead of coming right back, the power stayed away and the engine eventually shut off fully. I was thankfully able to coast my way out of traffic, into a left turn lane and then push the old girl (up a hill, no less) into a parking lot to pop the hood and inspect. To my surprise, what I found was that the wire that goes from the coil to the dizzy had popped itself completely off, explaining my sudden loss of power, the complete stall out, and possibly my other recent blips of power loss I've been experiencing if that connection has been shitty this whole time. So, I plugged it back in and the car fired right up when I turned the key. Since I was only a few blocks from work, I decided to hurry up and get there before I ended up being late for my shift. Much to my dismay, in that last half mile to work, I noticed that while the engine ran pretty smoothly, I wasn't getting as much power as I normally would, and looking at my boost gauge, I saw that it was because I was only getting around 5psi under full load, when I normally see 7-8psi. (Btw, my gauge is tee'd in right at the TB)

So here's where you come in:

First: I'm under the impression that something's gone wrong (maybe even horriby wrong?) with my turbo, and that it probably needs a rebuild, at the very least. Anyone have any ideas or thoughts that might suggest otherwise? I have also considered the possibility that the wastegate could be partially seized up or weakened in a way that doesn't allow me to build full pressure, but I think that the turbo seems a more likely culprit. Neither have been removed and inspected or rebuilt as of yet. Amusingly (or not), I was just discussing with a good friend yesterday that I wanted to do just that in the very near future. Certainly didn't want to be forced into it, though...

Second: The car clearly still runs but has a lot less going for it in the balls department. Given the possible condition of the turbo (and related items), is it (a) safe to still drive around while I find a remedy, or should I (b) just limp home and leave it there til it's fixed? Or is this (c) so dire that I need to quit driving it immediately and have it towed to wherever it's going to get worked on? I'm leaning most heavily towards option B, with a strong tendency to try to get to working on it immediately if the appropriate parts are readily available, but I'd love to hear your opinions.

Third: WTF happened? I mean, aside from what I already said, of course. I'm curious to hear what you guys think happened internally that resulted in screwing up my boost.

Thanks in advance.
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Chaos  



Joined: 07 Nov 2005
Posts: 289
Location: Newark, DE, US

PostPosted: Sun May 12, 2013 1:28 am    Post subject: Reply with quote

The more I'm thinking about it, the more I'm wondering if it's possibly not the turbo that's messed up, as it could just be a related component like maybe a plugged cat or a leak. Especially given that the turbo isn't making any new noises, still spools up, and doesn't seem to be smoking from what I can tell, I rather feel like a damaged turbo would be a bit more self-evident. And I also feel like a boost leak would also present itself as a loss of vacuum. But then, I only know just enough to be dangerous, so my "feelings" are probably less reliable than others' might be. Haha.

Just thinking out loud, so-to-speak.
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Chaos  



Joined: 07 Nov 2005
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Location: Newark, DE, US

PostPosted: Mon May 13, 2013 10:57 pm    Post subject: Reply with quote

So, after some more tinkering and the limited testing I can manage to do, everything else seems to be running fine overall and I seem to have the same amount of vacuum that I had before this incident, but I'm still not getting full boost pressure and you can certainly feel the inefficiency while accelerating. The turbo spools up fine, based on what I'm hearing, so I don't think that the problem is coming from inside the turbo.

So, it seems like I've developed a leak somewhere upstream of the turbo that doesn't manifest itself in a noticeable vacuum loss.

Still puzzling over where this could be, and would love to hear some ideas on parts to look at, as it'll be at least a few more days before I can get it smoke-checked, which (now that i think of it) may not even show the issue if it only presents under boost.
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Ponz  



Joined: 10 Jan 2013
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PostPosted: Mon May 13, 2013 11:16 pm    Post subject: Reply with quote

I have the same problem. It will run but lift off and it dies. I think it is the fuel
filter or fuel pump. Pull a plug and I bet it is clean and light brown. I will remove pump and filter this week.

Let me know how you make out.
vince
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Carrera RSR  



Joined: 08 Jan 2010
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Location: Somerset, UK

PostPosted: Mon May 13, 2013 11:18 pm    Post subject: Reply with quote

Remove the cable to the overboost switch and earth it. See if you can boost up then.

Look for leaks in the inlet/vacuum system.
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ideola  



Joined: 01 Oct 2004
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PostPosted: Mon May 13, 2013 11:22 pm    Post subject: Reply with quote

If the lower charge tube bracket has gone missing (which is a common problem due to the bolts backing out or shearing off), the lower charge tube will lift off of the turbocharger outlet, moreso as boost builds. So I would check that first.
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Chaos  



Joined: 07 Nov 2005
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Location: Newark, DE, US

PostPosted: Mon May 13, 2013 11:49 pm    Post subject: Reply with quote

Interesting theory Vince, I'll check the plugs.

Carrera, I had definitely not considered that over boost switch b/c I was under the impression that it cuts the fuel supply, which isn't happening here. But, ill definitely test it per your recommendation. Simply because I haven't checked it in quite a long time and ya never really know.

Dan, that bracket was the very first thing I checked, and it's still in place. That said, I did not check the gasket between the upper and lower charge tube. Nor have I checked the recirc valve, which I am getting a sneaky suspicion might be the culprit at large.

Many thanks for the input guys!
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ideola  



Joined: 01 Oct 2004
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PostPosted: Tue May 14, 2013 1:26 am    Post subject: Reply with quote

Next thing to check is the gasket at the lower charge tube interface, and also both gaskets at the upper charge tube to throttle body connection.
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Carrera RSR  



Joined: 08 Jan 2010
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PostPosted: Tue May 14, 2013 1:46 am    Post subject: Reply with quote

Yes, the over boost switch cuts the fuel pumps, but not fuel supply. The engine will still run at low revs as it sucks fuel through but not at high revs without pump pressure.

Check the short 2'' vacuum hose under the intake manifold. It runs via a hard pipe back to the turbo recirculating valve. If blown off you'll get no boost pressure.
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Chaos  



Joined: 07 Nov 2005
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Location: Newark, DE, US

PostPosted: Tue May 14, 2013 2:14 am    Post subject: Reply with quote

That is really interesting about the cutoff switch. Definitely never occurred to me to look at it that way. Also, that hose that feeds the recirc valve is another suspect that's high on my list. It's one of the few rubber vacuum connections that didn't just get replaced in the last week or so. Assuming that I should replace it ASAP, do you think it's crucial that I get the exact part ordered or would something easier to obtain be alright?

Dan, definitely going to check both ends of the charge tube. Top gaskets and seals are new, bottom ones: not so much, so they're getting looked at ASAP. On that note, actually, I just received my TMCC the other day. Is it safe to install before I get the water lines plumbed in? I figure that could allow me to skip dealing with all the middle and lower gaskets for the charge tube. Otherwise, see any problem with cutting myself new gaskets from gasket material I grabbed at the local parts store?
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Carrera RSR  



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PostPosted: Tue May 14, 2013 3:17 am    Post subject: Reply with quote

Its a fairly robust piece of rubber tube. Be surprised if its damaged but you never know. Its often the one piece people forget to connect and/or nip up the clips on as its hard to see and easy to forget.
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Chaos  



Joined: 07 Nov 2005
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Location: Newark, DE, US

PostPosted: Tue May 14, 2013 3:45 am    Post subject: Reply with quote

Overboost switch checks out.
Gasket between upper and lower charge tubes checks out, as do the rubber seals between upper charge tube and TB.
Meanwhile, found a surprising amount of oil in the intake... Didn't really expect that. (https://www.facebook.com/photo.php?fbid=10151470890968311&l=0671cd7ef9)

About to check lower charge tube gasket, and both sides of recirc valve (on the turbo and connection at the intake manifold)
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Grenadiers  



Joined: 20 Feb 2007
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PostPosted: Tue May 14, 2013 3:59 am    Post subject: Reply with quote

That little elbow on the recirc valve is n/a. If the gaskets on either side of the valve are toast, you'd hear a whistling air leak noise. Not sure you'd have a power loss though. As The Ponz suggested, check your spark plugs for a lean condition. If your recirc gaskets are back, autohausaz.com sells them. Cheap. If not available, I have a couple sets.
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Chaos  



Joined: 07 Nov 2005
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PostPosted: Tue May 14, 2013 4:15 am    Post subject: Reply with quote

Actually just installed a new one of those elbows, which I picked up from Dan not long ago, so they can't be 100% NLA. Though, it definitely took a long time to show. Haha

Anyway, engine power seems to be fine overall. The big issue seems to specifically be a boost leak somehow, somewhere. I keep a close eye on my boost gauge when I'm driving, and ever since the coil wire jumped off mid-acceleration the other day, I'm not getting my usual 7-8psi. It's taking longer to its build pressure and tops out at 4-5psi, but I can clearly hear the turbo spool up normally, and it does not match the reading on my gauge. Anyway, that's why I'm looking into all the turbo/intake parts first.

Meanwhile, the red/orange sealing ring for the lower charge tube seems to check out just fine.
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ideola  



Joined: 01 Oct 2004
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PostPosted: Tue May 14, 2013 4:55 am    Post subject: Reply with quote

Might be time for a smoke test on the intake tract. It could also be that you blew out the old crusty orings in the throttle body. Might consider a rebuild kit ($25 + shipping). This happened to me on the 937.

As for the elbows, the one at the recirc valve isn't the one that's NLA, that one comes with my kit. It's the one at the head breather adapter that's NLA.
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