06 Saab 9-3 ARC

the car is running rough at idle, only code given was a P0300. I have eliminated spark, fuel, and compression as the cause of the issue by using the activation feature on my tech 2 scan tool. cylinder 1 has a short on the coil when I pull it off, but it seems to be firing fine otherwise. all injectors are opening. and compression sounded fine when I cranked it.
The owner misdiagnosed the issue as a faulty throttle body or IAC.
when I went to look at fuel trim numbers everything checked out fine so I thought it was either timing or spark, after checking spark I'm left with timing; however, I do not want to pull this car's engine apart if it could possibly be a bad computer or cam/crank sensor, or some kind of spark control issue (the number one coil appears to have been spliced into before).
I have provided a video to illustrate what I'm talking about. Do take note that the exhaust on this thing is not cut off, the vehicle started running like this after about 10 minutes of idle, the only real change over the way it was before is the sound.
thoughts on the matter would be greatly appreciated!

do keep in mind I, like many others, do not possess a lap scope so any tests done will be done with a Plain-Jain multimeter

>>> <<<

Did I see the short term fuel trim numbers at +21%? Do you recall what the long term was?

The trim numbers along with the no start after running poorly suggests a fuel issue, to me. Have you tested for fuel pressure? Or, added alternate fuel to the engine while running poorly?

on the scan tool I have stft has two listings the 21% figure I think I should ignore because it seems to be an unchanging "fixed" value. ltft is always at 0%

I have not checked fuel pressure, but I have no reason to think it would be a fuel issue

Also!!! when I was testing the mass airflow sensor last night I tried unplugging it to see if there was any change. when I saw no change in performance I figured the sensor voltage (on the scan tool) would be minimum when i plugged it back in. however to my surprise, the sensor was reading perfectly fine after I had plugged it back in.

Dynamo786 wrote: on the scan tool I have stft has two listings the 21% figure I think I should ignore because it seems to be an unchanging "fixed" value. ltft is always at 0%

I have not checked fuel pressure, but I have no reason to think it would be a fuel issue

Also!!! when I was testing the mass airflow sensor last night I tried unplugging it to see if there was any change. when I saw no change in performance I figured the sensor voltage (on the scan tool) would be minimum when i plugged it back in. however to my surprise, the sensor was reading perfectly fine after I had plugged it back in.

So it's likely to be in open loop, then? Does the vehicle continue to misfire when driven? Get better, get worse?

I know that you doubt a fuel pressure issue, but I think the crank no start is a big red flag for fuel. Add in the dead lean O2 sensors when idling, too. Even if you didn't want to check fuel pressure, you could try carb clean in the intake during the no start and see if it helps.

nononono. you misunderstand. there is not an issue with a no start!
I'm having issues with the idle performance!!!

the vehicle starts fine and will run fine for about 5-7 seconds when first started. I thought this was caused by the car dropping in and out of open loop/ closed loop (which is likely what it is)
but after this initial period where it seems to be in open loop, the car goes straight to its chugging and random misfire; without seeming to have any issues with fuel trim!!
could it be possible that the sensors are all working fine but the E.C.U is refusing to use the data for some reason???
again when I unplugged the M.A.F last night there was no change. And when i did a cylinder drop test on both injectors and coils they all produced a steady misfire on their respective cylinder.
then after idling for a couple of minutes, it will shake and shudder then starts to make the noisy exhaust tone you can hear in the video where it sounds like it has got a big thumper cam in it and cut pipes. throttle response goes to s*** and the whole car vibrates much harder.

And as a side note, it seems that cylinders 2 & 3 both are missing more than 1 & 4, at least according to the misfire counter.

Tyler wrote: Did I see the short term fuel trim numbers at +21%? Do you recall what the long term was?

The trim numbers along with the no start after running poorly suggests a fuel issue, to me. Have you tested for fuel pressure? Or, added alternate fuel to the engine while running poorly?

Keep in mind that fuel trim will typically be high during a misfire. o2 & fuel in, o2 & fuel out.

I also noticed that cylinders 2 & 3 had twice as many misfire counts as 1 & 4... I would check for a milkshake in the coolant reservoir, do a block test, then check compression, in that order. Note plug condition when you do compression test obviously. I have had a couple cars that ran seemingly fine, but compression was low enough on a cylinder to induce a p0300. The limp modes/open loop revert are more sensitive on some cars than others.

i checked compression on all cylinders, they all were above 200 and there was no 'milkshake in the coolant.

that short term fuel trim number that was seen at 21 was a status number for the scan tool, i looked at it and it said it was "injector circuit open"