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Discussion Starter #1
2004 9-5T 2.3 automatic. Recently purchased the car with 83K miles on it. It accelerates wonderfully but idles poorly, especially while stopped in Drive mode. Looks like the idle stays about 900rpm in both neutral and drive so there's no noticeable difference there. Checked for error codes and none came up. Checked threads on similar problems and so far I've;

1. replaced the DI
2. cleaned the MAF sensor with MAF cleaner.
3. cleaned the throttle body throat and butterfly with TB cleaner.
4. changed the plugs to new NGK PFR 6H10s
5. meticulously checked every visible hose for vacuum leaks including spraying carb cleaner on all connections and intakes.
6. replaced the fuel filter.
7. Ripped most of my hair out.

It still idles badly. Any suggestions on what I could have missed or what I should try next would be greatly appreciated.
 

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Did you replace the dic because it was bad or did you replace it to rule out this same poor idling issue.

What did the old spark plugs look like, where they fouled?

Does it idle funny while in park or only when in gear (drive)? Also do you feel it rumble im the steering wheel or are the rpms just fluctuating?
 

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Think you need to define "poor idling" a bit better. Idle RPM at 900 is right where it should be so nothing wrong with that unless it is fluctuating up and down (like 750 then 900 then 1100 then 800 and so on). Agree with CarMD216 - inspect you spark plugs. Also, you check vacuum hoses - that is good - but also check the other major connections (pipes), such as the Cobra pipe to turbo, inlet pipe to TB, etc
 

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Discussion Starter #4
You can feel the rough idle on the steering wheel both in neutral and drive, although it's worse in drive. There are no visible RPM variations. Old spark plugs were not fouled and there was no difference when I replaced them with new ones. I replaced the DI with an extra one I had just to see if it was a factor and again, no difference. I checked as many vacuum lines as I could see and don't think I missed any. I sprayed around the cobra pipe to see if there was a leak there also.
 

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Sounds like motor mounts or center sub frame mounts or both! If ur brake lines arent to badly rusted have a competent friend hold the brakes and tap the throttle to see what kind of movement your getting. The subframe mount would usually cause a strange creaking and almost a popping sound when first putting the car in gear and reversing. Are you hearing any strange noises when dirst accelerating?
 

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Discussion Starter #6
No strange noises when first accelerating. You can also see and hear the engine slightly shuddering while idling like it's missing although I haven't gotten any error codes. I will do a brake torquing check tomorrow to see if there's any engine movement.
 

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While your out there (with the engine off) remove the small engine cowl...the thing covering your oil cap. Then pop the hose of going to the throttle body and look in there see if its carboned up or has any blow by oil sitting in the intake...if you have some teflon safe throttle or carb cleaner give it a whirl (expect the next few starts to be a bit goofy). If that plate is sticking could be a culprit... Additionally make sure to inspect the small vacuum hoses on the thorttle body. I have seen the electronics on the throttle body fail as early as 70,000 miles.

If both these ideas fail ive got a few more tricks to look at...
 

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Discussion Starter #8
I'll get on it the first thing in the AM. What were the other suggestions you had?
 

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Well lets rule the common stuff out before we bring out the big axes. One more small thing you could check while your back there is the map sensor connector. If your looking at the throttle body...It is located on the left and in the far corner but still on the manifold. Un plug the connector no need to remove the sensor and look at the end to see if any of the leads are corroded or burnt. You could also try wiggling the map harness when the car is running to see if it wants to play hide n go seek.

Here is what I found on google images which represents an older version of the sensor but the location is the same. Ignore the dipstick part.

http://www.twinsaabs.com/9-5_repair/PCV/new_dipstick.jpg
 

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Discussion Starter #10
Removed and inspected both ends of the MAP sensor and noticed they were clean with no corrosion. I sprayed contact cleaner on anyway and re-plugged. I'll try the wiggle test tomorrow. I also removed, inspected and cleaned the connector at the rear of the TB as well as the main hose going into the the TB.
 

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Well if mounts are good...pull the oil cap/dipstick and tell me if you see any gummy whitesh/yellow looking residue near the yellow plastic top...could be pcv system isnt venting right...also look to see how ur turbo gauge is acting...does is stay in the white or do you get good boost or to much boost...if all else fails get a compression tester and cross your fingers.
 

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How's the gas mileage? If it's good then you've probably got the standard SAAB rough idle.

I'd suggest checking your throttle body gasket. If it's compressed to the point where it's flush with the outside diameter of the throttle body you should replace.

I'm willing to bet you just need a couple new engines mounts. The cradle mount on the RF and transmission mount under the battery tray are the common suspects, and they make the largest difference from what I hear.
 

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Discussion Starter #16
No yellowish or whitish gunk on top of the dipstick and the turbo boosts normally. I did discover something else puzzling. I had replaced the plugs with everything else mentioned last week and just ran 250 miles with a can of 44K in the tank to deal with any fuel system issues it might have. Pulled the plugs again today and they're ALL pretty black and carboned up. Just the opposite of what I expected. Obviously now I'm running rich but why?
 

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Pulled the plugs again today and they're ALL pretty black and carboned up. Just the opposite of what I expected. Obviously now I'm running rich but why?
O2 sensor is high on the list of suspects. A faulty O2 sensor doesn't necessarily generate a CEL, mine didn't.

Faulty O2 sensors generate a low voltage, which the ECU interprets as a lean signal (as it should), and responds by enriching the AFR. It will keep enriching the AFR until it 'sees' a signal value that it 'wants' to see. Problem is, the ECU has no way of telling whether the signal from the sensor is correct or not. So, even if the AFR is actually correct (to start with), if the sensor is misreporting a lean AFR, the ECU will respond by over-fuelling...

Regards,
John.
 

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Would a Tech II scan reveal any codes the CEL is missing?
My understanding on this is limited, but any scanner will only read a code if the ECU has detected a problem. The ECU may log a code without generating a CEL if the problem is not major and isn't occurring repeatedly. In this case the scanner may read something like 'code pending', or something similar. I'm sure there are others here who know more about this than I do.

I do know from experience that an O2 sensor can be very sick and for the ECU to not recognise a problem with it. The pre-cat O2 sensor (and early 9-5s only have one O2 sensor) is the ECUs only direct 'window' on AFR, it's the one that the ECU uses to measure AFR, there is nothing (I know of) that the ECU can use to 'cross verify' the O2 sensor signal. The post-cat O2 sensor is used to monitor cat function, not AFR (though a wide discrepancy between pre and post cat sensor signals caused by a faulty pre cat sensor may trigger a cat related CEL...?).

Regards,
John.
 

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Discussion Starter #20
Thanks John. After being under the hood for 3 weeks thinking I must have fixed at least some of my issues with the recently-purchased car, I think I'll finally give my mechanic a shot tomorrow to see if he can pull a code or see something that was actually blaring in my face all along. I'll report any findings.
 
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