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Discussion Starter #1
I ve been trying to fix this Saab for 2 months now and a couple of days ago it started running like crap. The CEL was flashing and ran like a Harley. When I pulled the codes it gave me random misfire and four of the cylinders and nothing else :confused:. I would greatly appreciate it if someone can direct me to what it may be.

I ve replace the Coil pack, spark plugs and wires, check valves, knock sensor, fuel filter, air filter, oxygen sensor. I have no clue what it is
I was thinking it could be CPS or maybe a clogged cat, Throttle body maybe needs cleaned or Idle air control. But Im just wondering maybe someone else has had this problem
 

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I ve been trying to fix this Saab for 2 months now and a couple of days ago it started running like crap. The CEL was flashing and ran like a Harley. When I pulled the codes it gave me random misfire and four of the cylinders and nothing else :confused:. I would greatly appreciate it if someone can direct me to what it may be.

I ve replace the Coil pack, spark plugs and wires, check valves, knock sensor, fuel filter, air filter, oxygen sensor. I have no clue what it is
I was thinking it could be CPS or maybe a clogged cat, Throttle body maybe needs cleaned or Idle air control. But Im just wondering maybe someone else has had this problem
We are guessing here, rather than doing a diagnosis.
Check the quality of the connection to the coils.
Also check the work that was done...who did the work ?
 

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I will check the plugs and try some new spark plugs I read that if they are not exactly gapped then it could misfire.

I ve changed most of the things myself, and the mechanic at the shop didn t know what it could be. maybe Im missing something simple

Thanks for the reply
 

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When was the last time the fuel filter was changed?
Any white smoke? Any smoke period?
If you changed all that, maybe a CPS, but they usually totally fail or only fail when warm-they don't present with MCM's. I'd suspect MAF or fueling.
-Cm
 

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Discussion Starter #5
I changed the filter a couple weeks ago. i can t notice any specific period when it smokes. If you think it can be MAF, any certain way to test it before spendinng $300?
 

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A random misfire is not necessarily caused by ignition.
The charge may be either too rich (injectors ?) or too lean (air leak ?)..
Read and compare the plugs.
The fuel filter is a maintenance item, usually good for 100K miles.
CM may be on to something.
Do a search on testing the MAF...I am not positive as to the procedure.
 

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Discussion Starter #7
hmm I was driving the saab today and I noticed that every time I would reset my codes the misfire that shows up is always on the second bank.

Any clue what could cause this bank specific misfire?
One clogged cat maybe. I also had to replace my check valve for the 2 bank because it was baddly clogged
Does this come into play?

thanks just trying to figure this out :roll:
 

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hmm I was driving the saab today and I noticed that every time I would reset my codes the misfire that shows up is always on the second bank.

Any clue what could cause this bank specific misfire?
One clogged cat maybe. I also had to replace my check valve for the 2 bank because it was baddly clogged
Does this come into play?

thanks just trying to figure this out :roll:

Could be a fuel issue... clogged injector. You could try a can of techron fuel system cleaner... but if it's serious, that might not clear it.

How do the plugs look when you pull them? If you're not sure, take a photo and post it.
 

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Carefully inspect all your sensor cables for abrasion (possible shorts) or broken wires. Especially the coaxial cable on the knock sensors. An incorrect signal from the knock sensor can (will) cause the ECU to retard the timing on the entire bank 12 deg. (can be interpreted as misfire, bad O2 sensor etc.) Mine was shorted behind the alternator... Good Luck
 

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Discussion Starter #10
Im gonna try some of that fuel cleaner, and here in the next few days i ll try to post a pic of one of the plugs.

I ll do a visual inspection on the wires tomorrow and ill post back.

I measured the CPS wires, (online there was a video posted that the positive should be 12volts and the ecu wire should be 5 volts) my positive is fine but the ecu is showing .75

any ideas if this is correct?

Thanks again guys
 

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Check all vacuum lines for deterioration, or if any are disconnected. Namely, the evap canister purge valve and AIR control line.
 
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