Fuel trims out of control...
Thread Starter
TECH Apprentice
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From: San Diego, CA
Fuel trims out of control... Ok, this is a continuation of a previous problem. I installed some SVO 42lb injectors in the car and plugged in the new flow rates via HP Tuners.
I now get backfire on deceleration and on shifting when the car is in open loop. It goes away as soon as the car enters closed loop. Problem #1
My VE table is also off now showing lean pretty much across the entire table. Along with this, my O2 sensor readings don't match. One will be increasing while the other is decreasing. This happens mostly in the middle rpm ranges and seems almost random. They match up at idle. This causes my LTFT's to be way off (one reads +20 the other -20 as example). The STFT's are all around around zero. Problem #2
I checked for an exhaust leak and there are a couple slight leaks although nothing huge. One is around the driver's side cat and the other is towards the rear on the passenger side. I've also tried switching the O2 sensors around (although I didn't switch the driver side front yet) and nothing changed.
The VE table was dialed in before the injectors and it never backfired so it seems like it must be related to that although I don't know how. I've had a couple pretty knowlegable guys check out my tune and they said nothing was out of the ordinary with it. It also really confuses me that it stops backfiring as soon as it enters closed loop. All of this leads me to a few questions:
Does this sound like a tuning issue or a mechanical one?
Can an exhause leak throw off the O2's this badly?
Or, does it sound like my O2 sensors are going bad?
Is is dangerous to drive the car with the LTFT's so erratic?
It seems hard to belive the O2 sensors would have gone bad or developed a significant exhaust leak coincidentally right after i changed injectors. I don't really want to buy new O2 sensors and have the same problems. I'm not really sure where to go from here and I don't want to take it to a shop just yet. Any thoughts or ideas?
I now get backfire on deceleration and on shifting when the car is in open loop. It goes away as soon as the car enters closed loop. Problem #1
My VE table is also off now showing lean pretty much across the entire table. Along with this, my O2 sensor readings don't match. One will be increasing while the other is decreasing. This happens mostly in the middle rpm ranges and seems almost random. They match up at idle. This causes my LTFT's to be way off (one reads +20 the other -20 as example). The STFT's are all around around zero. Problem #2
I checked for an exhaust leak and there are a couple slight leaks although nothing huge. One is around the driver's side cat and the other is towards the rear on the passenger side. I've also tried switching the O2 sensors around (although I didn't switch the driver side front yet) and nothing changed.
The VE table was dialed in before the injectors and it never backfired so it seems like it must be related to that although I don't know how. I've had a couple pretty knowlegable guys check out my tune and they said nothing was out of the ordinary with it. It also really confuses me that it stops backfiring as soon as it enters closed loop. All of this leads me to a few questions:
Does this sound like a tuning issue or a mechanical one?
Can an exhause leak throw off the O2's this badly?
Or, does it sound like my O2 sensors are going bad?
Is is dangerous to drive the car with the LTFT's so erratic?
It seems hard to belive the O2 sensors would have gone bad or developed a significant exhaust leak coincidentally right after i changed injectors. I don't really want to buy new O2 sensors and have the same problems. I'm not really sure where to go from here and I don't want to take it to a shop just yet. Any thoughts or ideas?
Those injectors are a big step up from stock and I
think the first thing to look at is the math, followed
by logging injector pulse width and seeing if you're
sitting on the minimum limit value (which might want
shaved).
think the first thing to look at is the math, followed
by logging injector pulse width and seeing if you're
sitting on the minimum limit value (which might want
shaved).
Thread Starter
TECH Apprentice
iTrader: (1)
Joined: Oct 2003
Posts: 328
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From: San Diego, CA
Originally Posted by jimmyblue
Those injectors are a big step up from stock and I
think the first thing to look at is the math, followed
by logging injector pulse width and seeing if you're
sitting on the minimum limit value (which might want
shaved).
think the first thing to look at is the math, followed
by logging injector pulse width and seeing if you're
sitting on the minimum limit value (which might want
shaved).
Would reducing the min. injector pulse do anything since I'm not really at minimum? What about the short pulse limit? With it set at 3.997 the adder is being kicked in a lot.
