[BBartek]

Hi!

I've been home some troubles lately with my '94 NG900 (B204L, GT17 Turbo) and hope you guys can give me some advice.

1) Leak from exhaust manifold
First of all i noticed significant oil losses - there is oil between the engine block and exhaust manifold.

I checked the compression, results are:

Cylinder 1 - 11,2 Bar
Cylinder 2 - 10,8 Bar
Cylinder 3 - 9,6 Bar
Cylinder 4 - 10 Bar

The result for cylinder no.3 seems to be corresponding with solid oil leak from exhaust manifold - what are the possible causes?

2) Overboost
Since two weeks ago i have a problem with overboosting - until now the boost was running as it should, not exceeding the orange range of APC indicator.
Right now when i push throttle the boost goes far into red area, then there is sudden drop of acceleration (for about 0,5 sec) and then the turbo goes into read area again.

One thing i tried is to switch BPC from another NG900, but it didn't help at all.

Any ideas what should i try next?

3) Fuel mixture too rich (?)

While checking the compression i took a look at my spark plugs and it seems as though the fuel mixture is too rich - there is a lot of white build-up on spark plugs 1,2 and 4.
Spark 3 looks quite different from the other ones.

Any ideas what can be the cause? I checked other threads around here looking for answers about rich fuel mix and some suggested faulty MAF, but as far as i know MAF wasn't present in NG900?

Thanks in advance for any hints!

 

[MessingWithMySAAB]

If anything, your fuel mix looks mega lean.
Black = rich, chocolate = good, white = lean.
Also that buildup is nasty as all hell, at least take a wire brush and clean them up before you put them back in, setting the gap would be nice also.
But best would be to buy new plugs, don't forget to get the resistor ones.
Make sure your waste gate controller is hooked the right way around, if it's the wrong way around the turbo pressure will go up instead of down.
Also the drop of acceleration could be a fuel cut or a fuel pressure drop. Stock fuel pump i assume?

The zero fuss option to remedy this situation now would be to connect turbo pressure to the wastegate, this way you'll run wastegate pressure, which should be around 0.5-ish bar.
This will allow you to drive your car safely until you can find a proper fix.

Ps: i've seen engines that have been running lean start burning oil.

 

[BBartek]

Thank you for the reply MessingWithMySAAB!

Of course, i meant lean mix! I guess that's what happens when you write a post with one eye closed

I put new NGK BCPR7ES-11 spark plugs instantly.

What can be the cause of such a lean mixture?

Regarding the problem with overboost - i put new GT17 in place of the T25 turbo about 3 months ago and everything was running smoothly until now. So i guess the source of the problem lies with the turbo or its steering (BPC or charge air bypass valve perhaps?). There is too much boost, which results in fuel cut-off, the pressure drops and then builds up too much again - vicious circle closes...

Any ideas what should i check? As mentioned, i already switched the BPC, didn't help at all.

As far as the oil in exhaust manifold is concerned i made a check-up list:

1) Replace the PVC
2) Re-bolt the engine head bolts, as they were known to get loose overtime, causing oil leaks
3) Replace the exhaust manifold gasket

Any ideas what should i add to the list?

 

[MessingWithMySAAB]

1) Replace the PVC

You mean PCV? I guess that could be it, mine didn't burn oil when PCV was bad though.

2) Re-bolt the engine head bolts, as they were known to get loose overtime, causing oil leaks

Never heard of this issue, care to elaborate?

3) Replace the exhaust manifold gasket

Might as well since the gasket is leaking anyways, just don't strip the manifold studs, when i got my NG900 more than half of the stud threads inside the head were stripped.

Any ideas what should i add to the list?

First, connect turbo pressure to wastegate, if it's still overboosting then the wastegate actuator diaphragm is bad, or the wastegate is stuck. This will answer all of your turbo related questions.

 

[BBartek]

You mean PCV? I guess that could be it, mine didn't burn oil when PCV was bad though.

Yup, i meant the PCV. I found it in several posts and it seems a quick and cheap thing to check.

Never heard of this issue, care to elaborate?

While browsing through various posts about potential causes of oil leaks in exhaust manifold area i found official Saab instructions:
"It has been found that the clamping force of the cylinder head bolts diminishes after a period of driving and may result in oil and coolant leakage."
You can find the instruction here:
Saab procedure

Might as well since the gasket is leaking anyways, just don't strip the manifold studs, when i got my NG900 more than half of the stud threads inside the head were stripped.

Will do.

First, connect turbo pressure to wastegate, if it's still overboosting then the wastegate actuator diaphragm is bad, or the wastegate is stuck. This will answer all of your turbo related questions.

Will do.