Idle , vacuum & LTFT

MarcoCapone

Member
Aug 6, 2003
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0
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Hi guys,

I have a 2002 mustang GT with a vortech V2-SQ (stock pulley) and an AFM power pipe, it gives me around 9 pounds of boost at its peak. Since I had the kit installed, both P0172 and P0175 codes keep coming back. I did some dataloging using my SCT XCAL 2 (with the idle sequence as described by Joe at trick tuner) and it seem like both LTFT are at 0.75 at idle thus causing the CEL.

I have checked for a vacuum leak but found none, my vacuum at idle is around 17~18 mmHg (stock cam with idle at 800rpms).

The innovate wideband tells me that I'm right at 14.6 (the wideband is installed after the stock cats).

At WOT my car run like a champs and the only other thing I've noticed is the car is hard to start sometime (when cold). I've join 2 SCT log if you want to look at them, the first is idle for 30 sec with 15 sec at 1500rpms, 15 at 2500, 15 at 3500, 30 at idle a quick stab on the gas and 20 sec at idle. The second log is a 15 ~ 119 mph run (done in controled area :) ).

Download idle_log_5_Aout_2010.csv from FileFactory.com

Download 2 - WOT run.xls from FileFactory.com


What's my problem?
 
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I am not a tuning expert, but at the risk of stating the obvious, is the tune CORRECT for the size fuel injectors used? A mis match here could very easily cause a chronic rich condition in both banks.

>>>From the Ford service manual.
P0172 - System to Rich (Bank 1)

The Adaptive Fuel Strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a lean calibrated limit. Refer to Section 1 , Powertrain Control Software, Fuel Trim for more information.

Air Measurement System
MAF sensor (contaminated, damaged, corroded connector, etc.).

Fuel System
Fuel pressure regulator (vacuum hose off, diaphram leak, malfunctioning, etc.).
Leaking fuel injectors.
Fuel return line restricted.
Fuel rail pressure sensor (incorrect reading).
EVAP canister purge valve leak (when canister is full).
Base engine
Engine oil contamination
 
My tuner is telling me that the tune is right!

Someone knows if my vacuum reading is correct? Some people told me that it should be aroud 22?

21 to 22, 19 w/air-conditioning on, 17 is low enough to cause idle problems. I think you have a leak somewhere. After i use my a/c or defrost setting I turn the nob to off and notice some pressure leaking out, my theory if this is not done every time the a/c is turn off vacum leaks can persist.
You might consider a catch can to replace the hoses on your p/c system. I would check all of your intake couplers w/supercharger, make sure the bolts around the throttlebody are tight and around the lower and upper intake.
My honest opinion is there is a leak somewhere if the idle is that low.

My question to Burns, is there a direct co-relation between IAT and vacum readings?
 
My question to Burns, is there a direct co-relation between IAT and vacum readings?
Interesting question. The temperature of the air affects it's density. So at lower air temperatures, there is more MASS of air entering the engine.

I may be wrong, but I don't think that the temperature of the air (alone) will have a HUGE effect on the vacuum readings.

Vaccum is a measure of the pressure difference between the intake manifold and outside air. The exact amount of vacuum is depends upon a great number of factors. This is why it is often expressed as a range.

The vacuum reading may be slightly low due to worn rings/valves. It could also be caused by incorrect crank case venting, clogged exhaust, and the list goes on.....

IMO, most posts for driveability issues have a vacuum leak as the root cause. However, intake vacuum leaks often result in a LEAN condition. The OP's problem is unusal as it is a RICH condition in both banks.

Question? Will a wide band O2 sensor installed after the cats ever give a good reading? If not, that would mean that the tune is based upon flawed input (wide band O2).