two 3.0 OHV based cars, one with rough idle

I've been having a time with my 2001 Sable. I recently changed out the plugs/ wires as the car has 125K miles and the plugs hadn't been changed. The car at idle seems kind of rough and I thought the plugs
would improve things, but that didn't happen. I borrowed a friend's cheap code meter and no codes were shown and the readings I saw looked normal, maybe a slightly elevated long term fuel reading but otherwise ok. I also have a '00 Taurus with the same engine, but it at idle is much smoother and there doesn't seem to be much difference in OBD readings.
Any ideas as to the rough idle?
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If you are looking at the car with a scan tool, it probably is very limited in what it will tell you. Scan tools generally only give fault codes when the Check Engine light is on, and might provide freeze frame data of the conditions that existed at the moment the fault was detected. If the tool is up-scale, it might give live data.
An excellent value these days is an ELM327 module that you can find on eBay, and an ap for your phone. There is a lot of discussion about the Torque Pro ap that costs $4.95, but there are other aps also. You can experiment with the Torque Lite ap for free. The modules come in a wifi version and a bluetooth version. They will talk to the phone/tablet of your choice, and you choice will be weighted on whether the ap[ works with Apple or Android, which is driven by your phone/tablet. You can get the module for 20-ish dollars, and with the paid ap you will have under 30 dollars invested and can collect mountains of data. The module plugs into the OBD II data port.
For thle engine that runs rough, if you do not find joy in the electronic diagnostics, you ushould give serious consideration to a compression test.
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On 02/08/2015 01:08 PM, Jeff Strickland wrote:

You almost read my mind, Jeff. I just got a hold of a OBDLink SX which I believe contains the module you speak of. They have OBDwiz software, but a friend is going to let me use his laptop which has one of their pro software versions. I'm hoping to find out something beyond what a simple scanner shows. Will keep you posted. Thanks.
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Check out FORScan, a free software scanner exclusively for Ford, Mercury, Lincoln and Mazda vehicles that works with ELM327 and OBDLink adapters on Windows and iOS v6.0 platforms. forscan.org
Besides reading codes and data, it can also run manufacturer diagnostic tests and service procedures that normally require dealer equipment.
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On 02/08/2015 04:00 PM, Bob Bailin wrote:

Ok, I ran both the ScanXL Pro and Forscan programs. I choose a bunch of PIDS with special emphasis on fuel trims and injectors. I took a short highway trip and recorded data with each program separately. With ScanXL, at least two of the injectors momentarily change from no fault to fault at random times while driving; with Forscan, all injectors stay at no fault. So now I don't know what to believe.
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You can swap a faulty injector with one of the known good ones and see if the fault follows the injector. But first I would unplug and replug the connectors on the faulty injectors to make sure it's not just a bad connection. What PID is showing the faults and what is it measuring?
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On 2/7/2015 9:29 PM, Todd Williams wrote:

Ford had some issues with latter 3.0L heads with valve seat issues. Your does not seem new enough to be in this lot, but anything is possible.
You need to do a leakdown and compression test and see what you come up with.
bob
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