Tricky idle issue, but I have lots of data!!

[Medicman]

HI,
I have a real tricky problem with my idle. First the basics: My vehicle is a 2003 Mercury Sable, with 140k miles on it, it has the 3.0 overhead valve engine, identified with the letter “U” in the VIN number. The car was purchased ad is driven in northern Illinois, USA.

Now the problem: I have a bad idle when I first start my car. The idle will race when cold, it doesn’t matter if the car is in gear or not. By race I mean a RPM range of about 2500 to 3000. Very high for just an idle. As soon as the car warms up the car will drop the idle so low it seems like it will die, but it never does. Then the car seems to run fine.

I do have the luxury of a car scanner, and I do have a data capture from that tool. It is a TON of data, so I have just linked to it at the end of this post rather than post the data here. I don’t know much about the data from the scanner, but from what I have googled, the long term fuel trim for the second bank seems lean. It consistently reads around 8 to 10.5 when the short term for bank one and bank two along with the long term for bank one always seem to be around zero or just a bit negative. It seems it could be an injector issue or an oxygen sensor issue from what I have googled, but I don’t want to just throw money at the car without knowing for sure. Are there any good ways to test these parts? Or are there other parts I should be looking at? Any help would be GREATLY appreciated. I am a poor college student and can’t afford to take this into a mechanic.

Here is that data dump by the way:
https://docs.google.com/document/d/1usw9XjosBu2hn7LE120coTzIIBGiXssI00j4bjRPen8/edit?usp=sharing

Thanks again so much if you made it this far. Please let me know if I can gather any other data for you or answer any other questions.

Topic

[Its me]

I am not adept at Fords, so I will preface with that…

The LTFT numbers are not perfect but are within specs… And with 140k on the engine it is not surprising… When you start getting P017X series codes, then you should be concerned…

The data about your errors looks as if these are not setting a MIL light (Malfunction Indicator Lamp) So I am assuming these are pending codes…

If the MIL is on you should fix the known problems first….. Sometimes they take care of other issues in a roundabout way… I believe the first code (P1460) is an issue with the relay or a bad solder joint where the relay attaches.

The second (P1270) may be caused by high RPMs within a certain period… At startup high RPMs may be the cause…

To me it sounds like an issue with the idle air control valve or around that area…. Again… I am not adept at Fords and they do sometimes have some funny issues that are Ford Specific…

JMHO

-Karl

[Medicman]

Thanks for the fast reply. I should have put it in the first message, but so far I have replaced the plugs and wires, the IAC, the gasket between the throttle body and the intake plenum, and the elbow by the PCV valve. The PCV elbow was a vacuum leak, so replacing that gave me an improvement in the throttle but I still have the issue mentioned. Unfortunately I did not get the scanner until recently, so the scan posted is the only one I have.

[Its me]

OK… Good to know… BTW… Didn’t see any data from when the engine was cold…

I don’t think you have a vacuum leak, or if you do it is very small, the fuel trims should go rich if it does FWIW…

You may want to disconnect the MAF and see how it runs… Has the MAF been replaced/cleaned ever?

-Karl

[Medicman]

Yes, cleaned the MAF when I replaced the IAC. Also replaced the fuel filter then. FWIW the other stuff done at the same time was brakes and an oil change.

I’ll try runing it with the MAF disconnected. Can I just unplug the harness or do I need to take out the physical tube and sensor? What should I look for in terms of differences? Better or worse?

For the data capture while cold, I did try, but the scanner takes a whole setup process when you first plug it in, takes about 3 minutes, and by that time the idle issue is sorted out. The scanner resets as soon as you turn off the car or unplug it. No way that I can find to begin a recording when the car is first started. The scanner requires a “key on” then “key off” then “key on” again before you can begin the setup process for the scanner which includes inputting the car make model and year plus a bunch of other parameters through a clumsy 4 button keypad.

[Author]

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