Engine 2000 gt p0172 p0175 nightmare...
- Thread starter Richi22
- Start date
wmburns
SN Certified Technician
Have you replaced all of those parts in an attempt to "fix" the base problem?
We need to get you to put down the "parts changer" and test more.
Do you have an ODB2 scanner? Even better an ODB2 scanner with graphing capabilities.
ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/
If this were my car I would start by getting some base readings of the MAF, fuel pressure, and RPM's.
>>From Ford service manual
P0172 - System to Rich (Bank 1)
P0175 - System to Rich (Bank 2)
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
We need to get you to put down the "parts changer" and test more.
Do you have an ODB2 scanner? Even better an ODB2 scanner with graphing capabilities.
ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/
If this were my car I would start by getting some base readings of the MAF, fuel pressure, and RPM's.
>>From Ford service manual
P0172 - System to Rich (Bank 1)
P0175 - System to Rich (Bank 2)
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 pressure regulator (vacuum hose off, diaphragm 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).
- Engine oil contamination.
OneSick99GT
Active Member
Richie,
Does this car have aftermarket parts. Did the original owner upload a tune to the vehicle. Why did you replace the CPM? The forscan software burns posted is a lifesaver. I downloaded it and bought the adapter online to observe my bank 1 and 2 fuel trims while tuning, after burns recommended it. Download the software, buy the adapter, run the program and watch the bank 1 and 2 fuel trims and post the results here. If you have questions on how to graph the data I can help. I'm really familiar with forscan after using it for the past 3 weeks every single day dialing in my tune.
Before you get a vacuum smoke test done buy the adapter and download the software. The software is free and the adapter is less than 30 bucks on amazon.
Does this car have aftermarket parts. Did the original owner upload a tune to the vehicle. Why did you replace the CPM? The forscan software burns posted is a lifesaver. I downloaded it and bought the adapter online to observe my bank 1 and 2 fuel trims while tuning, after burns recommended it. Download the software, buy the adapter, run the program and watch the bank 1 and 2 fuel trims and post the results here. If you have questions on how to graph the data I can help. I'm really familiar with forscan after using it for the past 3 weeks every single day dialing in my tune.
Before you get a vacuum smoke test done buy the adapter and download the software. The software is free and the adapter is less than 30 bucks on amazon.
wmburns
SN Certified Technician
FWIIW, With negative LTFT's the PCM is attempting to take away fuel (rich). A vacuum leak isn't likely to cause this. The LTFT's should be positive when there's a vacuum leak. So if this were my car I wouldn't spend my $$'s on a smoke test just yet.
Some example of things that might cause large negative LTFT's are:
- MAF over reporting air flow.
- FRPS: disconnected or leaking FRPS intake vacuum reference line
- FRPS reporting wrong values to PCM. Cross check with an external gauge.
- PCM set up for stock fuel injectors where larger units actually installed.
- Leaking fuel injectors.
- Fuel injectors stuck open mechanically or electrically. Test with a "noid" style test light.
- O2 sensors stuck rich. Test by using an ODB2 scanner to look for lean/rich switch frequency. Easily seen on graph. Be careful here. IF the mixture is truly rich then it would be expected to not have any O2 rich/lean switches.
- bad PCM
- EVAP system drawing in gas vapors from fuel tank. To rule out block off EVAP line and see if anything changes.
- Base motor problem. Out of time. Leaking valves.
With the large number of parts already replaced with no "fix" and the fact that "professional" mechanics couldn't find the problem likely means that this problem will require some thinking "outside the box". Seems unlikely it will be something a simple as a bad sensor. Perhaps check the base motor's health with a compression test and/or leak down test. While we are on the base motor, what about the possibility that the motor has skipped time?
Sappy saying for the day: There is no elevator to success. You have to take the steps.
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wmburns
SN Certified Technician
Onesick99GT, It might be useful if you were to update and link one of your threads with some of your direct experiences using an advanced ODB2 scanner (like ForScan) to solve real world problems.
For example:
- Some lessons learned
- Example of how having quick access to data changed how you went about the trouble shooting "process".
- How the forums help
- Biggest surprise
- Anything else that you can think of that someone else that is not familiar with ODB2 diagnosis can learn from.
OneSick99GT
Active Member
Here is one thread from trying to troubleshoot a start and stall issue. Only after downloading the software and buying the adapter did I figure it out that my tune was in fact corrupted and I needed a new tune. None of the parts I replaced needed replaced to begin with. The software and adapter burns linked above gave me everything I needed to observe, troubleshoot, identify the issue, then remedy the issue.
https://www.stangnet.com/mustang-forums/threads/99-gt-no-idle.907196/#post-9148062
The tune for my maf sensor was incorrect. This can happen after upgrading to a different maf sensor which in my case that's exactly what I did. Or by drastically changing the airflow or fuel system, which would require a new tune. Remember maf sensors are used for measuring the amount of air coming in to the intake. My tune got corrupted in my case and I didn't realize this until after replacing my IAC, TPS, and maf sensor. I went through weeks of testing each individual piece according to my ford mustang manual thinking I also had an electrical issue. If I had only downloaded the software earlier and reviewed the maf airflow to voltage and a few other graphs I would have had this problem solved much earlier without throwing money at it. Ill post some pictures of my before and after using the software to diagnose my maf sensor issue. It just needed calibrated which any tuner can do that owns the software.
Below is a picture before the tune. Notice how much distortion there was on the bank 1 and 2 fuel trims. They were super high and super low. Once I posted this on this forum @a91what was able to tell me my tune was off. All for 30 bucks I solved my problem and knew what I needed to do to fix it.
The actual forum of my problem and how I resolved the start and stall issue can be seen below.
https://stangnet.com/mustang-forums/threads/sct-advantage-iii-racer-pro-software.907433/
https://www.stangnet.com/mustang-forums/threads/99-gt-no-idle.907196/#post-9148062
The tune for my maf sensor was incorrect. This can happen after upgrading to a different maf sensor which in my case that's exactly what I did. Or by drastically changing the airflow or fuel system, which would require a new tune. Remember maf sensors are used for measuring the amount of air coming in to the intake. My tune got corrupted in my case and I didn't realize this until after replacing my IAC, TPS, and maf sensor. I went through weeks of testing each individual piece according to my ford mustang manual thinking I also had an electrical issue. If I had only downloaded the software earlier and reviewed the maf airflow to voltage and a few other graphs I would have had this problem solved much earlier without throwing money at it. Ill post some pictures of my before and after using the software to diagnose my maf sensor issue. It just needed calibrated which any tuner can do that owns the software.
Below is a picture before the tune. Notice how much distortion there was on the bank 1 and 2 fuel trims. They were super high and super low. Once I posted this on this forum @a91what was able to tell me my tune was off. All for 30 bucks I solved my problem and knew what I needed to do to fix it.
The actual forum of my problem and how I resolved the start and stall issue can be seen below.
https://stangnet.com/mustang-forums/threads/sct-advantage-iii-racer-pro-software.907433/
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