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  #1  
Old 14th May 2012
duckacuda duckacuda is offline
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Default Jolt when accelerating

This weekend I finally got done replacing the thermostat and coolant temperature sensor on my car, as it had been reading about 175F before it would start to boil over. So clearly the sensor was bad but I have no way of knowing about the thermostat. I had also replaced the lower radiator hose so I had part of the intake tube off next to the MAF sensor.

Once I made my repairs and took it out for a drive, it started to lose power for a split second whenever I accelerate, at least it's mostly noticeable in second gear or higher. This causes a jolt whenever I try to accelerate, and it was especially bad today when I did extended highway driving to get to work.

I'm not sure what spark plugs are currently in the engine, my first thought was that they were fouled or possibly just the wrong plugs and I hadn't noticed any problem because the fuel mixture was always rich from the engine reading cool. But it almost feels like a turbo problem because I can't hear the turbo spool up as easily, or when it does, I get a big jolt. Do turbos usually fail in this manner?

Where should I look to figure out what's wrong? Does anyone thing it's connected to the work I did this weekend or just a coincidence?
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  #2  
Old 14th May 2012
TankTak TankTak is offline
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make sure you retightened any hose clamps you lostened or tacken off. also check for vacuum leaks as you may have disconnected something in the process and didnt even know it.

Also make sure the vacuum lin is hooked up to the turbo, ask me how I know this
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Old 14th May 2012
duckacuda duckacuda is offline
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Hmm, I wonder if something got inside the turbo. I had removed this pipe to gain access to the lower radiator: http://photo.platonoff.com/Auto/2008...eturn_pipe.jpg
(The horizontal metal pipe in that picture)

So if say, a leaf or something got inside the turbo through that hole, could it cause the kind of problems I'm having?
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Old 14th May 2012
TankTak TankTak is offline
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Originally Posted by duckacuda View Post
Hmm, I wonder if something got inside the turbo. I had removed this pipe to gain access to the lower radiator: http://photo.platonoff.com/Auto/2008...eturn_pipe.jpg
(The horizontal metal pipe in that picture)

So if say, a leaf or something got inside the turbo through that hole, could it cause the kind of problems I'm having?
Make sure you have a good seal around that pipe going to the cobra, also make sure you hooked up all the lines to the diverter valve if you disconnected it. I'm thinking if a leaf got in there it would blow right through as the turbo would shed it in a blink of an eye.
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Old 14th May 2012
duckacuda duckacuda is offline
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I didn't actually disconnect the diverter valve, or at least I didn't intentionally. It's possible that something got disconnected inadvertently though. I should check that. I did make sure to seal the pipe really well back on to the cobra though.

Am I correct that the little black tube coming out of the driver's side end of the pipe is a vacuum line? I wasn't really sure what it was so I just left it connected while I was working, so maybe I damaged it or disconnected it.

Last edited by duckacuda; 14th May 2012 at 11:19 AM.
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Old 14th May 2012
duckacuda duckacuda is offline
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Oh also, are there a lot of vacuum lines in the back of the engine compartment near the thermostat housing? It was difficult to maneuver a wrench back there to change the thermostat; maybe I damaged something there?
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Old 14th May 2012
TankTak TankTak is offline
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Originally Posted by duckacuda View Post
I didn't actually disconnect the diverter valve, or at least I didn't intentionally. It's possible that something got disconnected inadvertently though. I should check that. I did make sure to seal the pipe really well back on to the cobra though.

Am I correct that the little black tube coming out of the driver's side end of the pipe is a vacuum line? I wasn't really sure what it was so I just left it connected while I was working, so maybe I damaged it or disconnected it.
My car did the same thing and didnt notice any damaged lines until I actually disconnected the line from the diverter valve and found it cracked on the underside. Replaced that line and it was good for me, but my diverter valve soon failed so I replaced it with this
Quote:
Originally Posted by duckacuda View Post
Oh also, are there a lot of vacuum lines in the back of the engine compartment near the thermostat housing? It was difficult to maneuver a wrench back there to change the thermostat; maybe I damaged something there?
There are a lot of vacuum lines period, well a good 10' worth of them anyway. Take a look around and see if you could have possibly damaged or disconnected any of them. Also make sure you reconnected the intercooler hose, not sure if you disconnected it or not but it looks to me like u would have to replacingf the water pump
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Old 14th May 2012
duckacuda duckacuda is offline
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Cool, I'll have to take a look at the vacuum line after work. Hopefully that's all the problem is.

Are all the vacuum lines in this image:

...really the only vacuum lines in the engine? For 10 feet I would have expected there to be more than just those three somehow.

Also how will I know if the diverter valve is failing?
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Old 14th May 2012
TankTak TankTak is offline
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Yeah there are definitely more vacuum lines than just the three in the picture. Also you know when the diverter valve fails if you start getting a hooting sound while driving. Mine stoped holding pressure, tested it with a vacuum gauge and couldnt even get it to hold any type of pressure
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Old 16th May 2012
duckacuda duckacuda is offline
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Just thought I'd post this here too, in case anyone happens upon this thread in the future... (I started a different thread)

After all this my engine had stopped starting up; it would crank but not start, and there was a weird buzzing noise under the dash.

Turns out that was caused by the ground cable not being connected securely when I replaced my thermostat, causing the relays under the dash to buzz. And I wouldn't be surprised if that's what was causing the problem in this thread as well. However, in the mean time, I also replaced my CPS (crankshaft position sensor) as that seems to have similar problems when it fails, and now my car seems to run better than ever before, with no hiccups when accelerating.

TankTak, what exactly does this hooting sound like, and when exactly does it occur when driving? As I was just driving around it started hooting as the boost needle got up into the yellow area. It was a really low kind of hooting. This is a new symptom, but I don't think my turbo had ever properly boost before so if the diverter valve was failing I might not have known it.
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Old 16th May 2012
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Rarelibra Rarelibra is offline
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You should think about doing the GS bolt mod. It only takes about 10 min, and all you need is a vacuum plug that you can pick up from the local parts place or hardware store.
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Old 16th May 2012
duckacuda duckacuda is offline
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Originally Posted by Rarelibra View Post
You should think about doing the GS bolt mod. It only takes about 10 min, and all you need is a vacuum plug that you can pick up from the local parts place or hardware store.
Can you describe that to me? I haven't heard of that before, and I'm having trouble searching for what exactly a GS bolt mod is.
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Old 16th May 2012
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Quote:
Originally Posted by duckacuda View Post
Can you describe that to me? I haven't heard of that before, and I'm having trouble searching for what exactly a GS bolt mod is.
This is a big help

http://www.saab-tuners.com/en/hardwa...e-modification
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