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740 Why do I have a Saab valve on my car? And/or is this why I have no power under boost?

Update, fuel filter and plugs replaced.

Old fuel filter dripped brownish gas out, which left a nice debris residue after it evaporated. "Well, there's your problem..." Immediately the car ran smoother, but still no power.

Checked the plugs, and DANG my plugs got nasty FAST. In July I checked them and they seemed fine, the other day I decided to replace them just for kicks and giggles and three of them showed the charcoal-ish buildup of really nasty fuel deposits and such. Replaced with NGK BPR6ES @ .030" and the bulk of my problems seems to have gone away. I now have boost most of the time even when hot, although about half of the time it will still act like I have a huge boost leak. It seems to be getting better over time, and I'm guessing that the clean fuel is slowly cleaning the injectors out.

I will most likely eventually replace the injectors if I find a good new or rebuilt set of brown tops or equivalent that I can afford. May toss in some concentrated injector cleaner or something and see what happens.

Thanks for all the help, guys. I think I can call this issue closed and I am now moving on to the next problem, which is a big backlog of cosmetic issues and a state of general disassembly I need to address.

Yay for boost!
 
Indeed! I am quite pleased. I've even had a few runs where it approached or met the original performance when I bought the car. I think I'm going to dial the wastegate back in a turn or two and use the MBC to adjust boost from here on out though.
 
Well, spark plugs, fuel filter, wastegate actuator, boost pipes and intake hose, and a poorly plumbed external CBV. Everything contributed and although it's still not 100%, it's getting there.

Now I just need to figure out why there's such a dramatic difference between when it's hot and when it's cold.
 
Well, spark plugs, fuel filter, wastegate actuator, boost pipes and intake hose, and a poorly plumbed external CBV. Everything contributed and although it's still not 100%, it's getting there.

Now I just need to figure out why there's such a dramatic difference between when it's hot and when it's cold.

CTS could be bad.
 
that could also cause plug fouling. if coolant temp sensor is broken it may be getting over-rich mixture.

about the WGA: it should have some preload (like half the pin visible through the rod hole while the rod is detached)
dail in the desired boostlevel by using the boostcontroler. You should start to feel the boost from about 2200 on up. From 3000 on up the car should be hauling ass.

as for boostleaks: make sure the manifold has no leaking exhaust gaskets. And the turbo should be tightened down to avoid leaks between manifold and turbine. The compressor housing has a rubber seal or gasket between backingplate and snailhousing. If that leaks you also lose boost.
It's all in the details.
 
I'll check the resistance on the CT sensor this week and see what happens. I do have a fancy Volvo OEM replacement on the shelf just in case, but I don't have an intake manifold gasket handy, will have to acquire one before I try to replace it.

Wastegate actuator is defintiely slightly too preloaded, this is on my list of things to deal with. I picked up an extra 3 pounds of boost. Just haven't had enough time between drives for the motor to cool off, and this weekend I was fighting a sinus thing and didn't even leave the house. When it picks up power it's pretty early, when it gets hot and stops boosting I don't feel the initial power onset until ~3500-4000.

Fairly sure the exhaust side isn't leaking, I haven't seen or heard any symptoms of an exhaust leak. I will check the turbo mounting studs on the manifold though.

I will have to do another intake leak test and make sure there isn't any air going anywhere it shouldn't. If there is one it's likely going to be in the turbo itself, probably the seal you describe. If that's the case I'll just have to live with the reduced performance until I can afford a replacement - I'm not going to risk the downtime on the car to rebuild the turbo if I can swap in a known good replacement and get more power out of it at the same time. Not sure what my options are for a water cooled T3 or T3/T4 that I could ever afford, though.

I'll update when I find something.
 
On a B234F intake? It doesn't look possible. I was planning to pick up a set of metric crows-foot and a set of metric stubby wrenches to try it, but it sure looks like I won't be able to apply any torque to it to get the old one out.

I'll give it a shot. Might even head to the store tonight and try it tomorrow.
 
I dunno. Probably because the DOHC part of the car is the only thing on it that currently works correctly.

Also, you can fit a socket on it? I thought from the FAQ that you can't fit it over the sensor plug?

...

Holy crap, you totally can. I've been lied to! Looks like tomorrow morning I get to see if I can wrangle the socket in there and get some answers.
 
It turns out that I should not trust my memory when it comes to procedures. Reading and looking at the motor helps. That was the easiest job I've ever done on the car.

ECT sensor replaced. Butt dyno says the car is incrementally better, although traffic is so bad I can't find an empty stretch of road to see how much better. It does seem to be more consistent between cold and warm, although I still lose a lot of power.

I also did adjust the wastegate down to where it takes just a teeny bit of extension to get it on the wastegate arm.

Also re-did my leak test. The air is still going somewhere, and it's either the turbo or my brand new silicone air fittings, which are clamped to the turbo using new T-bolt clamps and an electric impact driver. No splits or leaks there. I'm thinking that seal behind the compressor housing is probably bad as Janspeed suggested. I am putting a bit of strain on one of my hose joins, so a new one with a bend in it is on the way, but I expect the leak is actually in the turbo somewhere - it sounds like it's in a big cavernous space. This seems like a likely candidate. Probably won't get to inspect it unless I run across a decent condition T3 of equal or better performance that I can afford. I really can't risk trying to rebuild the turbo on a time crunch since this is my daily driver for the foreseeable future.
 
Janspeed:
The compressor housing has a rubber seal or gasket between backingplate and snailhousing. If that leaks you also lose boost.
It's all in the details.

I don't follow this description because it seems that any rubber attached to the housing is going to melt. What is "backingplate" or "snailhousing"?

Maybe your leak test is pointing to CBV/BOV again? Is the turbo housing cracked?

What are the symptoms now since ECT replaced?
 
CBV is not leaking. Wastegate actuator is holding pressure as well. I also tested the entire pipe system from the intercooler to the pipe out of the compressor, which holds pressure all day long, and I tested going the other way (intercooler to throttle body) which also holds.

The leak is somewhere between the AMM -> turbo hose (brand new silicone) and the compressor outlet (also attached to brand new silicone). Basically it's as close to testing just the turbo housing itself as is possible. Here's the setup:

Line from compressor -> inflation attachment -> 'test cap' plug replacing AMM -> silicone elbow -> turbo inlet -> turbo outlet -> silicone joiner -> solid test plug.

I ditched the original cobbled-together hoses and everything from the turbo to the intercooler is new aluminum hard pipes with silicone joiners and adapters.

I don't see any cracks on the housing but I'm leaning towards something of that nature. I also can't easily check underneath because a friend has my jackstands and ramps.

Symptoms now are nearly perfect driveability, minus boost power when hot. I can stomp on the gas pedal and get no more backfires or struggling. Boost comes on hard when dead cold, then rapidly falls off as the engine warms. Boost gauge still shows pressure and responds to MBC adjustments but the power, while better than before, is still not up to par. Occasionally I will get a pull that feels like about 50% boost but I haven't found anything to explain why. When this happens, the 'felt' acceleration doesn't kick in until much later than usual.

All things point to something that gets worse with heat (e.g. cracked housing), and I can hear air whooshing through SOMETHING on the turbo when I leak test it, but I can't feel any air leaks. I wet my hand and ran it all around the compressor housing, but I can't feel anything. Previously I confirmed a leak this way when I could feel the air escaping from the wastegate actuator.

I'm wondering if it's possible for the turbo to be leaking internally somehow, but I don't have the faintest idea where it could be leaking. The shaft exhibits almost no play on either axis, it's like it's brand new.

The only other thing I can think of is that the silicone fitting on the outlet is supposed to be straight, but it's bent a little for clearance. I feel no leaks there, though, and the clamp on it is very tight. I've ordered a new 30 degree one just to be sure (also will help line up the piping a bit better) but I don't think that's it. I hope I'm wrong, of course.
 
Man, I have got to have a word with the guy who works on my car.... (I am occasionally an idiot. Only on days ending with "y".)

I utterly failed to tighten a hose clamp last time. Still doesn't fix the leak in the turbo area, but adding MORE leaks isn't helping! Tightened it down, reset the ECU (since I put in the new sensor I figured I might as well), drove for ~50 miles so far. I now have boost consistently across the entire gamut of engine conditions, even at 80mph I have some extra power. Still only about 75% of what I had when it was new, but it's definitely better!

New hose elbow should be here today and we'll see if that makes any difference.

Also, I am smelling gas occasionally, but I can't find any leaks anywhere. I'm quite alarmed about this, since the last time a car did this to me it burst into flames. I'm thinking the FPR leaking internally, the new fuel filter is dry as a bone and I don't see or feel any dampness anywhere on the motor. Probably not helping the situation.

Man my car is a basket case. I sure know how to pick 'em.
 
Oh it gets better. I put the new 45 degree elbow in and 1) the intake pipes are now pointed nicely at each other instead of being coerced into fitting 2) there's a noticeable improvement on the boost front! For once I was right!

But that didn't stop me from leaving one of the clamps on the CBV untightened, and so my joy was short lived as it removed itself from the intake plumbing with a surprisingly loud PSSSHHT. I think I might be too stupid to own a car.

Nothing's damaged but my already flattened ego, though, and the car is quite close to the speed where I bought it. I think it might be a little quicker today because of the sudden temperature drop as well, but I did a decent length run and still had full boost when it was warmed up.

So it looks like the original major problem was a leaky/ruptured wastegate actuator, compounded by a poorly plumbed CBV, then made even worse with a bad fuel filter which then ruined the plugs, made slightly worse with a marginal ECT, and made impossible to diagnose by my attempts to fix boost leaks which really just added even more leaks.

Kids, this is why we do stage 0 before we go fast, mmkay?
 
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