Bank 2 LTFT - Taurus Car Club of America : Ford Taurus Forum
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post #1 of 42 (permalink) Old 02-20-2016, 07:06 PM Thread Starter
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Bank 2 LTFT

I've just about got this Vulcan running like a top, but all that's left is the bank 2 being slightly more lean than it should be. LTFT on bank 2 climbs to about 8.5% and sits there at idle. At cruise it's a more normal 4% or so, but it doesn't match bank 1, which is 3% at idle and right about 0% at cruise. I completed a rather in depth check for vacuum leaks today with a cigar, and the system seems locked up tight. No smoke coming from anywhere. I suspected a lower intake leak but that doesn't seem to be the case.

So, it's down to either a "lazy" O2 sensor, or an injector with a reduced flow issue (I'm not getting "hard" misfires, but you can tell one or more cylinders on that bank are operating at reduced power, and the RPM gauge reflects this by wandering up and down as if there was a vac leak). What values for the 02 sensor should I be seeing on my scan tool? I have ForScan. I'll do some digging on my own but if anyone wants to be nice and point me in the right direction that would be great. As for injectors, am I correct in my assumption that the computer cannot control individual fuel amount per cylinder, but only increase overall fuel to that bank? I just want to make sure a bad injector is still in the running as a contender for this issue.

Speaking of injectors, is bank 2 really that easy to pull on a Vulcan? It's exposed and doesn't seem to require UIM removal to access. That would sure be convenient.

Also I forgot to mention I compression tested both banks and they passed with flying colors. 171-178 PSI on every cylinder. This was on a cold engine, with flood mode on. Don't think it's a valving issue.


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Last edited by ice445; 02-20-2016 at 07:30 PM.
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post #2 of 42 (permalink) Old 02-20-2016, 08:39 PM
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There is a runner control valve that is know to leak. I replaced the o ring on my 2006.
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post #3 of 42 (permalink) Old 02-20-2016, 08:56 PM Thread Starter
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Quote:
Originally Posted by Automender12345 View Post
There is a runner control valve that is know to leak. I replaced the o ring on my 2006.
I replaced that really early on when I got the car. Didn't see any smoke coming from there, unfortunately.


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post #4 of 42 (permalink) Old 02-21-2016, 06:57 PM Thread Starter
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Originally Posted by TechSurfer View Post
I've found that the cigar trick is not perfect at detecting vac. leaks. On my old car I found no leaks with a cigar, but did find leaks with a cheap-o vac. pump in a long hose running to my canister purge valve.

You might disconnect the electrical harness on each fuel injector, one by one, with the engine idling. If one doesn't affect the rpm drop as much as the others, it will point you to the problem injector/cylinder.

Have you ruled out the EGR valve? If it is not closing tightly due to carbon build-up or wear, it will cause idle problems and light misfire.
That's a good point. I did the test in the dark with a flash light as I found that was the best way to pick up smoke trails. I may have missed something; it's not impossible. With that said, that's a good point that if trims are good during cruise it makes an injector rather unlikely. I have not ruled out the EGR yet. I know it functions, but it may not be closing all the way. I don't remember there being much gunk in there the last time I had the UIM off, though.


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post #5 of 42 (permalink) Old 02-21-2016, 07:01 PM
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I've found that the cigar trick is not perfect at detecting vac. leaks. On my old car I found no leaks with a cigar, but did find leaks with a cheap-o vac. pump in a long hose running to my canister purge valve.

You might disconnect the electrical harness on each fuel injector, one by one, with the engine idling. If one doesn't affect the rpm drop as much as the others, it will point you to the problem injector/cylinder.

Have you ruled out the EGR valve? If it is not closing tightly due to carbon build-up or wear, it will cause idle problems and light misfire.
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post #6 of 42 (permalink) Old 02-21-2016, 07:04 PM Thread Starter
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What the heck is going on lol, my post got deleted? What I said before the forum ate it, was that I did the smoke test in the dark with a flash light to maximize my chances of seeing any leaks. But you're right, I could have missed something, it's not a perfect method. And I didn't really consider that an injector issue would likely show up worse at load, so that makes it less likely. EGR could be an issue, although it didn't look all that nasty when I had the UIM off, and I did spray some brake cleaner in there if I remember right. Still, I'll do the relevant tests and make sure it's working 100%.


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Last edited by ice445; 02-21-2016 at 07:08 PM.
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post #7 of 42 (permalink) Old 02-21-2016, 07:06 PM
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When you look for vacuum leaks, don’t forget the various “calibrated vacuum leaks” like crankcase ventilation (PCV valve dirty) and the evaporative emissions (EVAP) purge valve (which should ordinarily shut tightly).
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post #8 of 42 (permalink) Old 02-21-2016, 07:07 PM
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Sorry, I accidently deleted and reposted.
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post #9 of 42 (permalink) Old 02-21-2016, 07:08 PM
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A dirty or faulty MAF sensor can also cause positive fuel trim numbers because it “under-reports” airflow, driving the base air/fuel calculation lean.
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post #10 of 42 (permalink) Old 02-21-2016, 07:10 PM Thread Starter
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PCV Valve is new, and MAF was cleaned recently. MAF could still be a culprit though. I'll check the BARO PID and make sure it's reading reasonably close to actual.

EVAP purge vent could be a contender for sure. Isn't that on the tank side of the fuel system?

Also one thing I forgot to mention is that the oil pan gasket is leaking. Could that have any relation? I saw one post here a long time ago where someone said they were getting unmetered air through that gasket and it was causing issues.


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Last edited by ice445; 02-21-2016 at 07:12 PM.
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