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Discussion Starter #1
I have looked this up and seen quite a few threads, most of which end without ever divulging the issue.

I recently did the PCV update to the She Saab as well as replace the aging and cracking vacuum lines. In doing so I noticed that the brake booster vacuum line assembly was cracked at a one way valve, so I replaced it with a new one (not sure if I did this replacing the vacuum lines or if it was already broken). Note that the car has an automatic transmission, so its has a few bits that are different than my 5 speed.

The car used to start fine when it was cold, but now it stumbles on cold start and throws a P0300 code. I can keep it from throwing a code by giving the engine some gas when it tries to stumble, as if it were a carbureted car. Trouble is I can only do my testing once a day when the car has sat overnight. Once the car gets over the initial startup it runs fine and has plenty of power with no stumbling whatsoever.

I have gone over and over all of the vacuum lines, PCV system and brake vacuum lines as well as looking for any other potential vacuum leak. I also changed the spark plugs to no avail (but I was happy to see that the ones I pulled looked good).

I have not tried a replacement DIC, but will swap this one with the one in my Saab this evening to see if it makes a difference when I start the car tomorrow morning.

Any advice or insights appreciated.
 

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I can only imagine two things you could have done during that work: Left a vac line unattached or hooked up wrong or wiggled a connector that is marginal (corroded inside). You could try cleaning the DIC connector. Also, did you gap the new plugs to .9mm? That can help.

Other than that, it's time for a DIC swap to see if that's it.
 

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Discussion Starter #3
I changed out the DIC to no avail. The problem seems to be getting worse, so I think that something is failing.

I am beginning to suspect the Coolant Temperature Sensor. From the bits and pieces I have picked up researching generic car rough idle at cold start, the engine temperature sensor is often listed as one of the suspects (I am making an assumption that that would be the coolant temp sensor for a Saab).

When the car is warm the car runs well and pulls strong without hesitation or hiccup. It also idles smoothly when warm, which is one of the generic indications of a bad engine temp sensor.

I pulled the vacuum lines off one at time while the car was running and it seems there is no vacuum leak. There was a little bit of additional roughness when the individual lines were disconnected, but not too bad at idle. I pulled the brake booster vacuum and the car almost cut off, so I am crossing that one off the list.

I am going to replace the Coolant Sensor and if that does not work I am going to have to swallow my pride and take it to the shop to get it diagnosed. It may take a week or so before I get the part.

I have been a bit disappointed and frustrated at the number of threads on this site concerning this issue that did not post their final fix, so I am going to make sure that I post when I get this issue sorted.
 

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What year is the car?
Doubling down on this... if it's a T7 OG 9-3 you can pick up the factory sensor at a GM dealer. Only about $15 last I checked.

That's a quick change part (Pull connector off, deep socket on sensor, remove, stick finger in dike, spin in new sensor, tighten, re-connect. Ten minutes work. If you're not real coordinated or sure of the path, have an assistant stick their finger in the dike when you pull the old one out while you get the new one ready and screw it in.

FWIW, this isn't the normal failure mode for an engine temp sensor... but one never knows.
 

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Discussion Starter #7
So far no luck. However, the situation is getting worse. It used to be that there were issues on cold start, but the car ran strong after a minute or so. Now the car is starting to hiccup at speed and has cut off on me at stop a light. It did not throw any codes, which I thought peculiar. I had to put it in neutral and keep the engine at about 2k rpm at stop lights to make it home.

I am beginning to think its an O2 sensor, but it seems that it would have its own set of code. Even though I used my DIC in this She Saab and it had a rough start, I have not rulled out the DIC.

I am going to replace the fuel filter this weekend to cross it off the list. I would have replaced it last week, but I forgot to order the washers with the rubber inserts. Since I am now the custodian of two Saabs I ended up getting ten each of the large and small washers because they were so cheap - the shipping was more than all the washers.
 

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FWIW, you can reuse the copper ones if that's what's in there. Wet dry sandpaper flat on a flat surface (like a table saw), move the washers, not the paper, keep it flat on the surface. up the grits and finish at 400.
 

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It's not the fuel filter, and it's not the O2 sensor.

What year is the car? What engine? What transmission?
 
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