Negative Fuel Trims
02-14-2005, 08:00 AM
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Negative Fuel Trims Hooked my car up to a scanner and read the real time data. Im getting negative fuel trim readings accross the board. When hit on the gas it just sluggishly accelerates. What could be my problem? Bad Fuel Pump/Injectors?
I just changed out the Fuel Fliter. This is my daily driver so I need to fix things pretty quickly to keep her going. Thanks
Sharky
I just changed out the Fuel Fliter. This is my daily driver so I need to fix things pretty quickly to keep her going. Thanks
Sharky
02-14-2005, 08:07 AM
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Once you rule out an ignition problem,
try swapping your MAF back to the stock sensor section.
It's possible to run the granatelli ends on the stock sensor.
That should leans things back down.
You're running stock injectors right?
try swapping your MAF back to the stock sensor section.
It's possible to run the granatelli ends on the stock sensor.
That should leans things back down.
You're running stock injectors right?
02-14-2005, 09:33 AM
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Yeah Im still running stock injectors. I have also already checked the spark plugs and wires and they all look good. I don't have the stock MAF any more but I will see if I can borrow on to experiment with.
Any other suggestions? Thanks in advance.
Any other suggestions? Thanks in advance.
02-14-2005, 01:30 PM
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Light negative is a good place to be. Big negative means
you want some tuning or have excess fuel delivery. How
negative, is the key. It's surprising to see a GMAF car
with negative trims. Perhaps your tuner fixed it up for
the GMAF.
You don't want to worry much about the idle, what's
interesting is the trims at the point where it's "sluggish".
I used to see large negative trims at idle but small
negatives at cruise and upwards.
you want some tuning or have excess fuel delivery. How
negative, is the key. It's surprising to see a GMAF car
with negative trims. Perhaps your tuner fixed it up for
the GMAF.
You don't want to worry much about the idle, what's
interesting is the trims at the point where it's "sluggish".
I used to see large negative trims at idle but small
negatives at cruise and upwards.
02-14-2005, 02:37 PM
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Im seeing between 20-35% negative fuel trims at idle. Every so often at partial throttle it shoots up to 0% and then back down to 20 or so. Thinking of getting the Racetonix kit and then doing a 100-150 dry shot later on.Of course will be upgrading the injectors as well just don't have the cash right now to do both injectors and fuel pump upgrade on or the other.
Thanks
Thanks
02-14-2005, 08:55 PM
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If I understand you right, your base tune is over-fueling the
engine (but the closed loop trimming is pulling it back in).
Bigger injectors will just put you worse unless you get tuned.
I expect the drop to 0 is just where you're stepping over PE
threshold and trimming ceases (open loop).
engine (but the closed loop trimming is pulling it back in).
Bigger injectors will just put you worse unless you get tuned.
I expect the drop to 0 is just where you're stepping over PE
threshold and trimming ceases (open loop).
02-15-2005, 07:58 AM
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I had a mechanic friend of mine use a Snap-On scanner to get a more accurate view of what's going on with the engine. We finally got it down to the number one cylinder not firing properly. Swapped the #1 plug to see if that would affect performance but it didn't. So this leaves me with either a clogged or bad injector. My fuel pressure was OK so its not the pump. Ive checked around(I live in a very small town) and so far no luck on some one who can clean injectors. Any advice on how I can do this myself? Oh and by the way I had 395 random misfires within a 10-15 minute time frame while using the scanner all other cylinders were Ok.
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02-15-2005, 06:05 PM
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You have a very large cam with overlap. You should be able to bring your idle and part throttle back in range by adjusting the lower part of your MAF table to smaller numbers by a certain percent.
You need to get rid of those large negative trims. They will affect operation at other load values.
Your code is pulling a lot of fuel back. This probably has an effect on your AE and may cause a stumble or lack of power when you push on the gas pedal.
You need to get rid of those large negative trims. They will affect operation at other load values.
Your code is pulling a lot of fuel back. This probably has an effect on your AE and may cause a stumble or lack of power when you push on the gas pedal.
02-16-2005, 08:02 AM
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Well if that ain't the weirdest thing, just yestarday the whole thing went back to normal, no loss of power, stumbling nothing. Still think something is not right though. I will continue to monitor and contact the guys who tuned my ride about 7 months ago. I will mention the information I got from you guys and see what he says. Thanks to all for your input!
