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Old 03-06-2012, 02:36 PM   #1
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Default LTFT differ from each bank.

New to the scanning/editing realm and I noticed with my 4.3L that my LTFT'* between the 2 banks are different. This would include injectors between bank 1 and bank 2.

At times, I can almost see a 3.5 point difference between the 2 banks with the LTFT'* and injectors.

Any of those with HPTuners can take a look at my 37 minute run the other day.

http://www.kc2jga.com/blazer.cfg

http://www.kc2jga.com/blazer.hpl
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Old 03-06-2012, 10:57 PM   #2
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You may need to adjust the injector skew a bit. Look at the spark plugs for small differences in how they look, a bit darker, lean that injector out a very small amount.
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Old 03-07-2012, 08:29 AM   #3
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I don't seem to find anything that will change individual injectors.

http://www.kc2jga.com/blazer4.3stock.hpt
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Old 03-07-2012, 11:02 AM   #4
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if you've got the same setup as my vortec 350 i would think its more likely your crappy poppet injectors need cleaned or replaced. they have the individual conversion but its 225 for the 8cyl one and thats just hard for me to stomach for a $2500 truck that i have to keep putting money into.

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apparently wasnt expensive enough now the thing went up to 271
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Old 03-07-2012, 11:18 AM   #5
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It was just a few days ago that I had replaced the LIM gasket. When I had the spider assembly off, I dumped as much fuel out as I could and squirted as much carb cleaner in the fuel line intake port. I'm hoping I didn't botch this gasket job. I don't seem to be losing coolant, not hearing any vacuum leaks or seeing it with water.
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Old 03-07-2012, 12:47 PM   #6
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if you were leaking air it would be lean. why did you take yours apart, the ft'*? thats a good idea with the cleaner though, i have mine apart now i think im going to do that too while im trying to clean up the lower intake man. my fts are even but -28 to -30. i got a fpr a couple hours ago and upper and lower gasket set, going to take everything apart, clean, reassemble this weekend.
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Old 03-07-2012, 01:45 PM   #7
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No, I replaced my gaskets because they looked stock. They fell apart when I tried to pull them from the heads. So, yea, they needed replacement. Plus, I suspected the engine eating a little coolant.

Really, I don't know much about LTFT'* and STFT'*, other than I noticed there was a difference during the scan. Just hoping for some educatating today.
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Old 03-07-2012, 04:48 PM   #8
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mines munching coolant too, hopefully not the head gaskets i really dont want to mess with those.

Fuel Trim:

Fuel trim refers to adjustments being made dynamically to the base fuel table to get the proper ratio of fuel to air. Short term fuel trim refers to adjustments being made in response to temporary conditions. Long term fuel trim is used to compensate for issues that seem to be present over a much longer period. Fuel trims are expressed in percentages; positive values indicate lean (add fuel) and negative values indicate rich (subtract fuel). Fuel trim banks refer to the cylinder banks in a V style engine. Cylinder #1 is always in bank 1. Fuel trim is generally calculated by using a wide set of data values, including front O2 sensors, intake air temperature/pressure (or the more elegent air mass sensor), engine (coolant) temp, anti-knock sensors, engine load, throttle position (and change in throttle position), and even battery voltage can effect fuel trim. Long term fuel trim generally should not exceed +- 10%.
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Old 03-07-2012, 05:34 PM   #9
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Think of it this way. If you have a exhaust leak, it will register lean and your LTFT will be positive because it'* adding fuel. If you have a vacuum leak it will read rich, and your LTFT will be negative because it'* pulling fuel. Does that help any?
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Old 03-07-2012, 05:51 PM   #10
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Yes it does. Thank you guys for clarifying that.

But still, I don't see anywhere that I can adjust that.
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