[redd69]

OK, I need some ideas as to what's wrong with my '96 900SET. It tends to mis-fire a little during acceleration. It will idle just fine but misses randomly during acceleration. I took it in to the saab guy to have him hook it up to the computer and it came back with a "camshaft timing sensor" malfunction. Now, he said there isn't really any such sensor but it indicates something else. We tested the Direct Ignition Cassette and sure enough one of the coils was not working properly. The one spark plug would only fire about 20% or the time. So I replaced the DI cassette ($335) and the spark plugs too and it is still doing the same thing. I'm now wondering if it isn't some other part of the ignition system or if it isn't fuel related. The car has 81000 miles and has been relatively well maintained. If anyone has any ideas as to what might be going on I'd really appreciate any assistance.

 

[mg_td]

it does have a crank position sensor i thought?

 

[redd69]

maybe that's what the trouble code was then?? either way... the mech said there really isn't one but I'm beginning to doubt him. I did look in my Haynes manual and it doesn't show any info regarding either sensor.

 

[Slaab4life]

Huh, I started off saying their is definitely a camshaft sensor, but I'm wrong. Their is a camshaft sensor integrated into the n/a models with the rotory distributor. So technically, their is no camshaft sensor on your SE. Their is however a crankshaft position sensor. This may be what the code is actually referring to. Your mechanic may want to try replacing that:
http://www.eeuroparts.com/(0hrgurfs40q4xn45n32qci55)/productdetail.aspx?searchResults=1&code=4688
If standing in front of the car facing the engine, its low, to the right hand side.

 

[PMI]

If a car with a DIC is misfiring at speed but not at idle, even after new plugs and a new DI, the problem can be as simple as a partially clogged fuel injector. At idle enough fuel gets through. At higher revolutions there is not enough fuel, or the spray pattern is so far off that the cylinder will not fire. I would run some injector cleaner, strongest suff you can find, before doing anything else.

The CEL code probably has nothing to do with the CPS.

As far as I know, there is no code for CPS (CRANK-shaft Position Sensor) failures, the car will simply stall or not start. On a turbo with a T5 ecu, it does not do much. See furter below for part number and price if you feel you need one.

If you do have a CEL code, please post it, that can help with some advice.

Assuming the code was P0340, this is a generic code. So, if your mechanic is an indy and looked it up in a manual, he would find something like this:

Camshaft Position Sensor A Circuit (Bank 1 or single sensor)
from http://www.iequus.com/obd_def.asp

Note the use of the word "Camshaft", NOT "Crankshaft".

There is no camshaft sensor on a turbo, this function is performed by the T5 ecu, which senses the firing order of the cylinders on startup by feedback from the sparkplugs, via the infamous DI cassette (that is part of the reason why we have resistor plugs).

What happens inside the cylinder depends on a lot of things. Spark plug, DI cassette, injectors working correctly. So, if the mechanic went by the code and your symptoms, he would have tried plugs and a new DIC first.

As for the crankshaft position sensor:

pasting from eEuroparts.com:>>>
Part Code: 9177221
Part Name: Crankshaft position sensor
Part Brand: Genuine Saab
Part Cost: $39.60
Part Description: Crankshaft position sensor for any 96-98 900 2.3L, 99-03 9-5 4cyl, 99-02 Viggen, 00-02 9-3 all.
<<<

Reference: Haynes, Chapter 4A, section 14.7 (Motronic ecu) and 15.20 (T5)

 

[redd69]

I was also thinking fuel as well but wasn't sure... I watched the mech do the trouble code "download" and I didn't see the actual number but it was a nice machine and it just said "camshaft position sensor malfunction". The mech did say that there isn't an actual CPS but it indicates other things. He immediately tested the DIC and it did misfire on the one cylinder. I replaced the DIC and plugs and am still having the problem. I am taking your advice and running FI cleaner through the fuel system and hoping that clears it up. I guess if that doesn't work I may have to conisder new injectors??? I appreciate your help guys!

 

[PMI]

...if that doesn't work I may have to conisder new injectors???

I would not rush to buy new injectors based on what you posted so far. They are pricey, and you can have then cleaned by ultrasound or something like that. Even the cleaning is expensive, partly because they are a pain to get to.

Here is a thread I used to help diagnose some of my un-even firing issues:

http://www.saabcentral.com/forums/showthread.php?t=41117

Not everything applies because the DI cassette and the plugs are new already, but scroll down to posts by bkrell. He lists two other things I found on my car... dry DI cassette boots, and compression problems.

In my case, the normal compression test was ok, but a leak down test showed over 70% leakage on one cyl. due to an intake valve that was sticking open. It returned to normal after running a couple tanks with another solvent with a fancy name, "Ventil-Sauber" (means valve-clean) from Lubro-Moly...

You might as well make sure the IAC and the inside of the throttle body are clean while you are at it, best to do it all in one pass. My IAC was ok (cleaned about two years ago), but the inside of the TB was full of black crud.