Leaning Out... maybe... - MustangForums.com


4.6L (1996-2004 Modular) Mustang Technical discussions on 1996-2004 4.6 Liter Modular Motors (2V and 4V) within.

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Old 08-19-2011, 04:28 PM   #1  
Ram1216
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Default Leaning Out... maybe...

Hello everyone. I'm new here, but I also just bought my mustang in place of my WRX. Don't regret the decision at all.

I bought the car about a month ago, and it had a terrible tuning on it. Mods are as follows (2001 Mustang GT 5spd)

BBK CAI, X-PIPE (catless), SHORTY HEADERS
FLOWMASTER 40s
4.10 Gears
Kennebell 1.7L, 7psi, Boost-a-Pump
Snow Performance Methanol Injection
36lb Ford Racing Injectors
Performance Thermostat (Kid didn't know much about it)
Glowshift Wideband a/f and Boost Guages

The tune that was on it only dyno'd 307.16rwhp and 317rwtq peak.

The car ran way too rich at WOT and way too lean at lower throttle.

I called Kennebell, and ordered a chip from them, and it runs great, perfect a/f at WOT, and anything past 1/4 Throttle. Here is what concerns me:

At just before 1/4 Throttle, until the motor is past 2000rpm, it will lean out to ~17.2 a/f. As it approches 2000rpm, it jumps to right where it should be. Also, in between shifts it will spike on the guage to almost 20 for an instant then come back down. It will also read 20 when compression braking while the engine is holding back. Before I contact Kennebell and Pay 100 or 200 for them to adjust this, I thought I should make sure this is definitely a problem. At anything over 1/4 it performs flawlessly, and at WOT the a/f reads 12.4 up to 4psi, then 11.8 from 4-6psi, and 10.9 at peak boost, which my research has stated to be pretty much optimal for power and safety... Thoughts would be much appreciated! Thanks! And I'm glad to find this forum. Love it already.
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Old 08-19-2011, 06:54 PM   #2  
dwtjr3
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IMHO i would put that $100 or $200 towards a dyno tune. Your car will feel completely different after it. That is by far the best way to get your car running right (well as long as you get a good tuner)
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Old 08-19-2011, 11:58 PM   #3  
Ram1216
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Yeah... the car is actually starting to I guess "learn"... most of the lean issues have started to disappear.
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Old 08-20-2011, 09:27 AM   #4  
Blackvenom01
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i would take it to a dyno turner thats the only way your can figure out whats going on!! shifting gears it will lean out thats why you get whats called lean pops aka cackle
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Old 08-20-2011, 11:47 AM   #5  
Ram1216
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UPDATE: Car is no longer running lean on acceleration of any throttle position. It seems to have figured itself out in that regard. Now the only issue still remains the compression braking. It hits 20 a/f or higher when at 0 throttle and ~2000 rpm coasting down in gear.
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Old 08-20-2011, 12:25 PM   #6  
sn95_331_GT_ yellow
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when theres no load on the motor its supposed to lean itself out...

my AEM WB just goes blank when i let off, so the AF shoots up past 20:1 but theres no danger to it really, just as long as it corrects itself when you throttle on again...
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Old 08-20-2011, 03:39 PM   #7  
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correct it will make out when you downshift!!!
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Old 08-22-2011, 05:40 AM   #8  
uberstang1
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I would take that car to a tuner and have it tuned , canned tunes are garbage IMO and can cause you alot of headache if you pop the bottom end on your motor. If your worried about it pull a plug and see what it looks like.
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Old 08-22-2011, 05:40 PM   #9  
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Quote:
Originally Posted by Ram1216 View Post
UPDATE: Car is no longer running lean on acceleration of any throttle position. It seems to have figured itself out in that regard. Now the only issue still remains the compression braking. It hits 20 a/f or higher when at 0 throttle and ~2000 rpm coasting down in gear.
That is normal behaviour, the injectors are shut down during closed throttle deceleration. There are several scalar values in the tune related to this:


  1. The first as shown above is the amount of time at closed throttle deceleration before the fuel injectors are shut off once all conditions are met--this is the only value I have changed in my tune, from 4 to 1 second to make the shut-down happen faster;

  2. During closed throttle decel the fuel injectors remain shut off until reaching this RPM;

  3. RPMs must be higher than this to allow the injectors to be shut off;

  4. Vehicle speed in MPH that the fuel injectors are allowed to remain shut off, after coasting down to this speed, they will restart;

  5. The above value, minus this value, is the vehicle speed in MPH that you must be above for the fuel injectors to shut off again (hysteresis, I.e. if you coasted down to 24 MPH, then accelerated to over 25--say 30--and did another closed-throttle deceleration the injectors will not turn off again);

Note that there is no danger of a lean firing with this scheme as there is NO fuel to burn.
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