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Discussion Starter #1
Hello everyone,

I have a 2009 Saab 9-3 2.8 with XWD. My car has been tuned to Stage 2 by Brian at Vtuner and I cannot figure out what my issue is for the life of me.

The car experiences boost cuts. At WOT it will cut from 15lbs to 5lbs and I can feel the power loss. It happens most of the time and will sometimes randomly give me full boost.

The car also randomly stalls on idle, ONLY after It was in gear and I shift to neutral. I can always bump start it when this happens because the car is moving.

It also randomly bounces between 600rpm and 1,200rpm when I'm at a standstill at a light. This doesn't always happen.

I have tested for vacuum and boost leaks and I currently do not have any.

Brian says it's an electrical issue. He provided me with graphs that show that boost cuts while airflow stays at 100% which is impossible. I will attach the graph below. I will also attach a graph that shows when my car stalls during a drive.

To quote what Brian has said about the boost cut in his emails to me:
"It is looking like an electrical issue of some kind. I'll try to walk you through what I am seeing that makes no sense unless it is an electrical issue. I've highlighted the traces for a section of your data log where the boost cut is occurring. If you simply look at the data for the MAF, throttle position and boost (E55Boost is the actual boost pressure) then we see a moment where the boost drops to 0.4 but the throttle is still wide open and there is no drop in mass airflow - that is simply impossible - if the throttle is open and the boost drops to zero the MAF value should drop precipitously at the same instance."


The car has been scanned with a tech 2 and has no DTCs related to my issue. The only known issues the car has are interior lights shorted out and the driver's seat does not move.

I need the car so I haven't been able to take it apart and check all the wiring harnesses. I may have to do that at some point.

I'm praying that someone has experienced this before and may have a solution that I have not come across. I've checked over a 100 boost cut threads and haven't found anything similar. All help is really appreciated.

Cheers - Matyas
 

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As a sanity check, I would reinstall the stock tune temporarily and see if the problem still occurs.
 

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Discussion Starter #3
Unfortunately I'm mechanically at a point where the car will not start on a stock tune. I appreciate the suggestion though. I'm willing to try anything.
 

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I suppose it's possible one of the limiters (boost, torque, etc.) in the tune is set a little low, but unlikely given it's Vermont Tuning. Do you have their full stage 2 tune then, including the hardware?
 

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Discussion Starter #5
I have full stage 2 hardware and then some. Ill post my comprehensive mod list. I also have the stage 2 tune that has been checked over and altered a little bit by Brian.

Mod List

20% heat reflective tint all around 90% heat reflective tint windshield
700CC Bosch fuel injectors
Brembo big brake kit front wheels
Coilovers
Custom muffler delete
Do88 air intake
Do88 charge pipes
Do88 intercooler
Do88 turbo inlet
Eaglesport tires
Iridium spark plugs
Krona downpipe
Krona midpipe
Rear headlight mod
Short throw shifter
Super 19T compressor turbo upgrade
Uniden R3 radar detector - hard wired
VTuner ECU tune stage 2
Window tint NYS exemption
 

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Discussion Starter #6
tried stock tune just to see if I could get lucky, but as suspected the car leaned out and wouldn't start. So I reflashed with the most recent tune update.
 

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Car won't lean out if not in boost. Drive it like a normal human being and see if these 2 issues still persist.

The car also randomly stalls on idle, ONLY after It was in gear and I shift to neutral. I can always bump start it when this happens because the car is moving.

It also randomly bounces between 600rpm and 1,200rpm when I'm at a standstill at a light. This doesn't always happen.
 

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Discussion Starter #8
Okay I will reflash it stock, drive it conservatively and get back to you
 

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What I wonder, is it heat related? If you took out the car cold and just sent it (yes, I know not ideal to beat on it on cold oil, but once or twice won't ruin anything) does the boost cut still happen or is it only after driving awhile and car is nice and hot?
 

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Heat related, maybe. The ECU is commanding the turbo bypass valve open at the point it cuts boost, so something's upsetting it. It looks a lot like it's hitting one of the limiters.
 

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Discussion Starter #11
Those two symptoms still occur when I have the stock tune. The car is hot but ill try it when its cold when I can
 

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Discussion Starter #12
A few more notes. The car seems down on power in general recently and I am running the correct tune. It used to be faster. Its very hot here around 91 degrees but when I'm not sitting in traffic using an esid2 I see my intake air temperature is around 100 so it isn't crazy hot. It does go up when I'm sitting still for awhile. So I'm not getting horrible 120 degree heat soak temperatures all the time
 

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hot air=less oxygen
 
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Discussion Starter #14
Another thing I wanted to note. I just went out with all this heat and it gave me boost without cutting through 2nd which isn't surprising but also through 3rd which doesn't happen often. Still the car felt way underpowered. The boost cuts returned on and off after that
 

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There are a number of possibilities and questions in my mind. Ignition is retarded to near zero for some time before the fun starts. Is the ECU getting excessive knock indications (real or imaginary)? Does the fuel flow (injector on time) increase right before the boost cuts? Is the turbo bypass valve working correctly, mechanically? Is the waste gate working correctly? What does intake air temperature look like when the boost cut occurs? The low sampling rate on the data makes it hard to see transient events.

One last Q that's easy: are you at sea level when you see the boost cuts?
 

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Discussion Starter #16
All I can answer from those questions is that the boost cuts occur at any intake temperature. My Temps are usually 60-70 degrees but while its 90 here I've been seeing 100 degrees. I have boost cuts at both temperatures. I am also right around sea level. About 700 feet or so average elevation above
 

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Cool. I was worried I might overlook you're at altitude, but you're not living in the Adirondacks. ;) It's hard to tell from your first pic, but the VPWR V (system volts?) does a suspicious looking drop intermittently, including right before where the boost cuts. If that's real, the ECU would panic for sure.
 

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Discussion Starter #18
Brian has been seeing voltage drops like that in all my logs. I'm just not sure what could be causing that. But that's awesome to hear that the voltage drop is a cause. That is a great place to start diagnosing at least. Thank you all so much for your help so far. You have gotten me farther in 24 hours than I've gotten in 2 weeks!

Keep the good suggestions and observations coming! :)
 

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Discussion Starter #20
I have a good battery place that will test it for me for free tomorrow. Today I was watching voltage as I drove.

I have about 14.0 - 14.2 Volts most of the time. After a boost cut I would see it drop to 13.5 or so AFTER the boost cut.

By far the worst voltage I got was when I shifted into neutral and revs dropped. When they dropped i saw voltage drop to 13.0 - 13.1volts.

If voltage dropped below 13 to 12.9 or 12.8 thats when the car would stall on me and it would stay around 12.7 until the bump start took it back to 14.1

This was only a half hour drive so ill continue to watch voltage, but I got these drops everytime I went into neutral or if I had a boost cut.

Diggs I took your advice and gave it the business before it was fully warmed up and I experienced 1 underpowered pull with full boost and one pull with a boost cut.

I'm really hoping its just a bad battery as that is still under warranty, but I fear it might but much worse.

Thank you guys again for the suggestions. Y'all are what lead me to even paying attention to voltage as I drove.
 
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