05-13-2016, 09:47 PM | #1 |
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strange LTFT
I am having some very strange issue with my LTFT at idle. A little background, I am running a vortech supercharger with an OFT tune, 9psi pulley, stock injectors. When I first turn the car on it is in injector mode 1 (port only) and the fuel trims will climb until maxed out at 39.4%. If i blip the throttle a few times the idle will switch to mode 2 (DI only) and will idle fine. normal driving conditions seem to be fine as well. Any thoughts as to what could be causing this?
I have already checked for vacuum leaks or any exhaust gasket leaks. |
05-13-2016, 09:56 PM | #2 | |
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05-14-2016, 12:42 AM | #3 |
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I recently had a problem with my STFT at idle. It was max because a o ring poped on my port injector fuel pump, causing it to leak back into my gas tank. Idle was crap as well. It was on a DW pump
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05-16-2016, 09:10 AM | #4 | |
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I'm between bad injector or in tank pump. Were you able to log a low fuel pressure before you pulled the pump? |
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05-16-2016, 10:19 AM | #5 | |
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If you do not have the correct fuel pressure it will cause a rich or lean condition. Example low fuel pump output would cause a low pressure not allowing the injector to spray the given volume per pulse. Over pressurized would make a rich condition. Stock pressure should be around 54psi. A clogged injector will run lean as a stuck open injector will drop raw fuel on the piston causing a rich condition. Don't rule out the ignition side either. Try pulling the plugs and look for a fouled plug. (black and wet) or look for a bright white which would be lean..
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05-16-2016, 11:42 AM | #6 |
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The main reason I'm leaning toward it being a fueling issue is when the motor is running on DI everything looks fine.
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05-16-2016, 09:35 PM | #7 |
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05-16-2016, 10:16 PM | #8 |
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I've actually had the same thing with the same setup (OFT300 package); at initial startup the fuel trims are all over the place and then settle down to basically +/- 5~10%, including idle and cruising.
I asked Shiv about this and he said that it was normal. Can anyone confirm? Also can anyone tag Shiv? Not sure how it works on here. |
05-17-2016, 02:45 AM | #9 | |
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05-17-2016, 06:43 AM | #10 | |
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That sounds pretty normal. However I am much farther out than 5-10% |
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05-17-2016, 08:55 AM | #11 |
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I consider +- 5-10% unacceptable; I would be up in arms if a tune had me sitting at more than, at a maximum, +-5%. Even fuel variance from the pump, at an extreme, won't cause more than 5%.
Popping an o-ring off on your fuel pump means faulty installation; if you use both o-rings supplied with the DW pumps, you can't have a leak that causes that failure. Typically 3 are used for installations to prevent that with this car. OP are you getting a bank 1 or bank 2 over rich, and/or a fuel trim bank mismatch code? I need more info to help diagnose. |
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05-17-2016, 07:28 PM | #12 | |
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The guy working on it told me "Pulled the pump, and an o-ring broke. Caused a fuel leak in tank at the pump. Made a Delrin spacer to keep the o-ring where it needs to be since your old one from your old pump didn't fit." Maybe they lost or did not use all the o rings supplied |
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