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4.6L General Discussion This section is for non-tech specific information pertaining to 4.6L (Modular) Mustangs built from 1996 to 2004.

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Old 09-17-2012, 06:08 AM   #11
camhar25
 
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Vehicle: 2001 mustang GT
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Took the car to the stealer last week for diagnosis.They said the airflow meter numbers were way out of wack.Changed the airflow meter and the car is still running rich and the idle is up and down or stalling out.Blowing black smoke when idling and still no check engine light.Any ideas?I also instlled a new idle air control valve,and a temp sensor thinking these could be bad.In all my experience the check engine light should be on.
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Old 09-17-2012, 07:33 AM   #12
cliffyk
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Originally Posted by schmallz View Post
Hey cliffy,

I'm throwing p1152, and only p1152(and p1000) i've swapped the o2 sensor from side to side, changed nothing. So i then decided to take the car down to JBA in San Diego.

They have tested the wiring harness and even managed to hook up the o2 sensor directly to the ECU. Still acted funny. The heater core in the o2 sensor isn't heating up for what ever reason. After a full day of testing and diagnosis, they still are at a complete loss for what is going on.

It idles fine when I start it up, but when I start crusing in 3rd gear or higher it will sputter as the short term FT slowly climps to 1.250(I can watch this on my tuner)

Any ideas?
Sorry I missed this--the O sensor heaters are all connected to the same +12V source, the same source that powers the EVAP stuff, and switched to ground via MOSFET transistors in the PCM.

If the heater is not being powered as it should then there is a wiring problem with the +12 V source or the switched ground wire running back to the PCM--or, sit down for this, the MOSFET in the PCM is blown.

Here is a kludgy sort of test/solution. Get an older 4-wire O sensor with a 6.0 Ω heater; on our stock sensors the heater is 3.3 Ω, more about this in a bit. The Bosch 13275 is a good pick as it was used on a bunch of mid-90s cars and is usually cheap--$25 to $30.

The 3.3 Ω heaters cannot be continuously powered without burning up, however the older 6.0 Ω units can be--so installed the older sensor with the sensor output wires connected normally, but with the heater wires connected to ground and a switched (HOT in run) +12 V source that can supply at least 3 A.

This will result in a functioning, continuously heated O sensor that will make the PCM happy...
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SOLD! - 2003 GT, UPR X, FRPP 24lb/h, Magnaflow, PP 70mm TB & plenum,
Delta Force tuned, Steeda UDPs, Ralco flywheel,
RAM HDX clutch, 3.73s, 262 rwHP/305 lb-ft.

New ride (7/1/2013) 1998 Mercedes SL500-5.0L 32V VVT 326/347 HP/tq


Engineering is, at its base, making what you want from what you have.
At its extreme it is making what you want from what you can get.
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Old 09-17-2012, 07:46 AM   #13
cliffyk
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Originally Posted by camhar25 View Post
Took the car to the stealer last week for diagnosis.They said the airflow meter numbers were way out of wack.Changed the airflow meter and the car is still running rich and the idle is up and down or stalling out.Blowing black smoke when idling and still no check engine light.Any ideas?I also instlled a new idle air control valve,and a temp sensor thinking these could be bad.In all my experience the check engine light should be on.
They didn't charge you for the new MAF did they? If so then at least get the old one back from them.

As I said in an earlier post failing front O sensors would cause this, and could do it for a while without throwing a DTC; monitoring the short term fuel trims will also reveal this situation. The O sensors cannot be properly tested in situ without an oscilloscope, however armed with a scope their output at idle should look like this:

Click the image to open in full size.

The signal will oscillate ("switch") 3 to 4 times per second between 0.2 V and 0.85 V. However the voltage range can be as low as 0.0 V to 0.6 V and still not throw a DTC, thing is this will be telling the PCM the mix is lean and it will compensate by adding fuel--up to +25% before throwing a code.
__________________
-cliff knight-
SOLD! - 2003 GT, UPR X, FRPP 24lb/h, Magnaflow, PP 70mm TB & plenum,
Delta Force tuned, Steeda UDPs, Ralco flywheel,
RAM HDX clutch, 3.73s, 262 rwHP/305 lb-ft.

New ride (7/1/2013) 1998 Mercedes SL500-5.0L 32V VVT 326/347 HP/tq


Engineering is, at its base, making what you want from what you have.
At its extreme it is making what you want from what you can get.
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Old 09-17-2012, 07:46 AM
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