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I’ve got a 2000 Ford Taurus with the 3.0 liter “ohv” engine. I was scanning my car, particually looking at the fuel trims. And I noticed that everything seemed fine most of the time. In PARK, at idle, my LTFT’s were around +6% on both banks and STFT were around 0% on both banks. But when I’m idling in DRIVE, with my foot on the brake(like at a stoplight) my LTFT’s go anywhere from +10% to +16% on both banks and my STFT’s are around +3%. Any other time other than idling in park or idling in drive, the fuel trim numbers are perfect. So, is this normal? If not which direction should I go in to diagnose what’s wrong? Thanks in advance for the feedback!!!
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+1 to the above posts.
What happens to those fuel trim numbers when you are driving?
Anything +/-10 is generally ok on your LTFT.
It does show that your PCM is adding fuel to correct a lean condition.
Keep us posted.
My fuel trims stay close to 0% while driving. I’m sure I got a vacuum leak somewhere. I’ve replaced pretty much everything but the lower intake manifold gasket to correct the leak. But, my question was why the big difference in LTFT between idling in drive and idling in park? Why would the car go even leaner as soon as I put it into drive?
I’ve been watching Eric’s videos for a long time… They are very informative… He’s one of a kind. I’ve learned so much from watching.
I also have a question about my alternator and/or battery. I watched the video about diagnosing alternator faults and I am wondering if my alternator and/or battery is dying on me. I did some testing this morning. The ambient temperature was 48F. I tested battery voltage before I started the car. It was 12.29 volts.
With the car running at idle, with no load. Voltage was anywhere from 14.14 volts to 14.29 volts. The voltage seemed to constantly fluctuate between those voltages.
Then I turned all accessories on and at idle it dropped down to 11.72 volts. It stayed between 11.72 volts and 11.78 volts.
Then with all accessories on with engine rpms around 2500rpms, the voltage went to 13.72 and stayed very close to that number.
Now with this information I think the battery is getting weak and alternator may be going too. According to the video the voltage shouldn’t be that low at idle with all accesories on. But a few other people told me that since the voltage did go up when I raised the rpm up to 2,000rpm’s, that the alternator was okay. So, what do you guys think? I also checked positive side and ground side and everything was good there.
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