boost low and bouncing

[abdukted1456]

OK, so my wife's car is acting up...
1999 9-5 lpt with td04 conversion, custom stage 2 software.
204,xxx miles

The car was misfiring badly with a p0300 (generic misfire code)

I brought it in to a Saab tech and they said the ECU was bad and not in control, it couldn't connect to Tech2. Got the ECU reflashed, and the throttle body replaced. Better, but not better enough. The car still doesn't spin the tires and boost is either way too low, or builds up and bounces up and down. (watching on calibrated boost gauge, the car is/was lpt so has none on the dash)

There is also a loud "thunk" sound coming from the drivers side under quick changes from boost to vacuum. Things like letting out the clutch too quick, when the car starts up, letting off the gas quick , these make the "thunk" sound. I was thinking maybe some engine mount, or perhaps the brake booster or bypass valve solenoid against the firewall there? The clutch is a brand new aero clutch, so it leads me to believe this sound is related to vacuum and not mechanical in nature.

The car has recently replaced silicone vac lines. Tech2 showed no airmass deviation so theoretically there is no boost or vac leak.

I tried new plugs several times with no improvement. Tried another DI with no improvement.

FPR is pretty new since it was part of the stage 2 package.

I found a check valve that might have been backwards, going to the TB. I reversed it to match the arrow/direction on my other 9-5, and still no improvement.

I plan to try some testing with a spare BPC, and also to investigate the operation of the wastegate. I know the arm is attached, but perhaps the actuator is sticking due to rust or something.

When mcrowley and I put on the TD04 I had broken the sensor for boost/air on the delivery pipe by accident. The car boosted wildly all the way to fuel cut (22psi or something) so I know the turbo works! yes, I replaced that sensor

The car kind of stumbles on decel like it is maybe going to stall but so far hasn't.

Fuel pump is new. Fuel filters are always done at the mileage intervals specified. New 02 sensor installed recently.

I am probably going to try and clean the MAF with this MAF cleaner spray I have.

Clogged (original and stock) cat?

Anyone have any ideas or what it could be or how to further diagnose? The tech seems to think that the alternator is going (the interior lights pulse a little) and that is messing up the operation of the car. I am not sure I buy that, because if so, then why replace the TB and say that was the problem. I think he does not really understand this.

[aireeca]

That clunk up by the driver's side...did you drop the subframe at all to do any work recently?

[abdukted1456]

Originally Posted by aireeca

That clunk up by the driver's side...did you drop the subframe at all to do any work recently?

It had a clutch and front axles, oil pan dropped and cleaned, done last year. But the clunk just started in the last month or so.

[aireeca]

Gotcha. Sometimes, if the subframe goes down, the bolt needs a re-torque after some driving. That doesn't sound like what's going on, though.

My '01 9-3 went through a weird stumbling period that nothing fixed until they reflashed the ECU with a tune other than the E-85 one I had been running. Good luck getting it sorted out!

[abdukted1456]

took it for a spin with the "W" hose from BPC to Wastegate detached. It boosted something like 22psi, then another time more like 14 psi. I am not sure what to make of that, though

[Tweek's Turbos]

Have you bypassed the valve on the firewall? It has lines going to it from the intake mani, and then to the bypass valve.

[abdukted1456]

Originally Posted by Tweek's Turbos

Have you bypassed the valve on the firewall? It has lines going to it from the intake mani, and then to the bypass valve.

That is definitely on my list of things to try...

[abdukted1456]

OK, I think I solved this while doing an oil change this weekend.

The driver's side clunk sound, I found the sway bar end link was not attached to the sway bar on that side!
It seems the little bushing/joint insert thingie has broken from the metal bar. Will be installing a new one...

Now for the low boost and boost "pumping"... and p0300 misfire:
after paying a "master Saab tech" who cited his trusty techII that claims there is "ZERO airmass deviation" and therefore no boost or vac leaks, and who installed a brand new ECU and throttle body which did not fix the problems...

GRRR

I decided to go old school and look at this in detail myself.

There was a check valve that is backwards. Fixed.
There was a vacuum hose not attached. Fixed.
Better, but still stumbling at idle and surging with low power.

I then found a massive split in the hose from the intercooler to plastic delivery pipe.

I wrapped it in duct tape and it doesn't hold in the boost but now I am seeing 15+ psi and no stumlbing at idle/decel...

replacement hose is on the way!

[VAGGEN]

Nice detective work!