Does anyone know how to understand SCT logs?

Discussion in 'SN95 4.6L Mustang Tech' started by mat82284, Jul 19, 2010.


  1. mat82284

    mat82284 Member

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    I seem to be having a new problem every other day lol. We'll anyways after swapping batteries i seem to have a new issue. The other day I was driving and just so happen to be logging at the same time my car dies out on me while coming to a stop. This actually happens twice. I have been using up a lot of gas lately and I was logging to find out why. My long term fuel trim is show in high numbers 1.24+ and so on at times. Here is some logs that I did with my SCT livewire. Sorry the livewire only allows me to log 6 things at a time for a max of 60seconds so i did multiple logs. Can you take a look at them and tell me if they look normal?

    Also if a maf was going bad or is dirty would it make your car run rich? What else could cause it to run rich?

    my engine is a 5.1l stroker with comp cams, ported heads,vortech v2 intercoolerd. That is the major parts. I also have a SCT mass air and im running my maf as draw through and its been tuned for it. The car ran perfect a year ago when tuned, but now its changed. I've also reprogrammed my ecu and it didnt fix the issue. I also replaced my front 2 02 sensors since I got a code saying they were bad a few weeks to a month ago.

    If needed i can re-log with different settings let me know.
    http://home.comcast.net/~mathew82284/MustangLogs.zip
    #1
  2. wmburns

    wmburns SN Certified Technician

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    What Model Year are we dealing with? Please post the full DTC's as they can make a difference in the troubleshooting.

    LTFT of +1.24 (+24%) is near the limit of fuel trim.

    BTW, positive (>1) LTFT means that the car is LEAN and the PCM is adding fuel. If running rich, the LTFT would be negative (<1) to take fuel away.

    So how do you know the car is running rich?

    As for an example of things that can cause the mixture to run rich, misfire, bad/miscalibrated MAF, excessive fuel pressure, bad fuel pressure sensor (or regulator), incorrect tune for the injector size, bad O2 sensors.
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  3. mat82284

    mat82284 Member

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    I actually have no trouble codes at the moment but in the past i've gotten (below) and I've also replaced my 02's. The only reason I assumed rich was because of this..

    P1132 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Rich - Bank No. 1
    P1152 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Rich - Bank No. 2

    I did get this code a week ago, erased it and it hasn't come back. Could I have a bad sensor wouldn't the code have come back right away?

    DTC P0190 (Fuel rail pressure sensor)

    As for the tune, the guy did a great job and the car ran fine before. The car is tuned for every part correctly that I'm sure of. Could a dirty maf cause this? I seen some oil (small amount) in my powerpipe and thought maybe it reached the sensor?

    edit: I was doing some research online and found that im using the old fuel rail sensor. Its the one that came with the car and i have 115k miles on it. It's probably time to replace now. I found the new part number online 3R3Z-9F972-AA I'll call my local stealership and hope its around $75 since thats what it is online
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  4. wmburns

    wmburns SN Certified Technician

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    You still did not supply the MY of your car.

    Oil on the MAF could cause serious problems (even small amounts). Clean it with cleaner designed for it. But how is the oil getting to the MAF?

    Suggest starting by checking your fuses. If the MY is 1999-2004, check F2.8 in the CJB. Not a bad idea to check them all. Next check the battery cables. Ensure they are clean and tight.

    Then have the alternator tested. Look for excessive AC ripple. Also ensure the alternator is keeping up with the load. Not a bad idea to monitor the voltage during a run.

    Check all of your vacuum lines. Esp the one to the FP sensor.

    The P0190 DTC is just a likey to also be a LOOSE WIRE to/from the sensor. Is there an extension harness on the FP sensor?

    Data log your fuel pressure. This is going to be the most telling parameter if the problem is a fuel pressure sensor. Note, if you are dealing with a bad connection, this can easily explain why the problem comes and goes.

    FWIIW, this could be the fuel pressure sensor. The PCM is getting bad information which is causing the FP to go all over the place. There is a limit to how large the fuel trim values can grow. But the other DTC's could result from the FP problem. Of course this could also be a VACUUM leak.

    Also looked at the logs. The fuel trim values are not in percent but are in a multiplier form. 1.2 indicates that 20% additional fuel is being added (this is a large correction that is very near the limit!).

    >>>
    P0190 - Fuel Rail Pressure Sensor Circuit Malfunction (FRP)

    The comprehensive component monitor (CCM) monitors the FRP sensor to the PCM for VREF voltage. The test fails when the VREF voltage from the PCM drops to a voltage less than a minimum calibrated value.

    VREF open in harness.
    VREF open in sensor.
    VREF open in PCM.

    Verify VREF voltage between 4.0 and 6.0V.
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  5. mat82284

    mat82284 Member

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    Wow thanks alot thats alot of information. My car is a 2000 mustang.

    As for the oil, I've found some in my power pipe but it doesn't actually reach the maf because of all the curves. I was thinking that maybe light mists of it was hitting the sensor some way. Not like getting soaked or anything.

    I checked my whole car for vacuum leaks and found none. I doubled checked that sensor and nothing. I tested the wires with a multi-meter and there getting power and its grounded correctly.

    How do i Verify VREF voltage between 4.0 and 6.0V? Is that something I can log or do I need to use my multi-meter to test the voltage? Also would the car have to be in the on position or actually turned on if using a multi-meter?

    Thanks for your help!
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  6. wmburns

    wmburns SN Certified Technician

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    Have you checked the alternator? Have you checked the battery? Have you checked the fuses?

    If you are thinking that a bad battery can't cause a running car to just stop, you are wrong. The battery is required to excite the alternator's field coil. Without a strong battery, the alternator can not keep up with any sudden increase in load. Prime symptom is the car suddenly quits for no reason. Apparently runs fine when restarted.

    Bottom line, today's car will simply not run well without a stong battery and alternator.

    OBTW, data logging the fuel pressure is a better method to test. If the VREF is outside of normal ranges, this will likely show up in the logs as zero or an impossibily large number.
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  7. mat82284

    mat82284 Member

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    Again thanks for your help!

    I actually replaced my battery a few days ago with a brand new one. I also replaced my alternator a year ago with a 200amp one and I had it tested before replacing the battery. So that's not the problem.

    I'll go and data log today and look at the fuel pressure.

    I do have another question. Aslo as a side note I removed the plastic pprv in the tank on the 03 cobra hat. That little fuel nozzle that's on the fuel lines. We'll when ever I hook up a tire gauge it reads 0. I've never tried with the car on though. Should it read 0 when the car is completely off? What about if the key is in the on position? It still shows 0. I know a tire gauge isnt something to really test on, but before I swapped my engine I remember being able to press down on that little middle thing and have fuel shoot out. It doesnt do that anymore, I'm assuming is because of the pprv delete though.
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  8. wmburns

    wmburns SN Certified Technician

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    The PPRV is a check valve that is there to hold fuel pressure while the engine is off.

    No PPRV, no fuel pressure between starts.
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  9. mat82284

    mat82284 Member

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    Oh ok then that makes scene.

    I re-logged with different scenarios. I really wanted to floor it and log it that way but I didn't want smoke to come out. I just remembered that every time I hit 5krpms and im into boost black smoke comes out of the tail pipes. That was my biggest indicator of being rich. I'm hoping its just a sensor or something small.

    Take a look at the logs and let me know what you see. Thanks again!

    http://home.comcast.net/~mathew82284/logs.zip
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  10. wmburns

    wmburns SN Certified Technician

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    The FPDC and IACDC is of questionable value for this problem.

    Is TP_V the throttle position voltage? If so, what are the units?

    What are the MAF units of measure? How would it present if the MAF were to max out?

    If you look at the logs, note the LTFT. The PCM is adding up to 20% MORE fuel (the value of 1.2 means 20% more). Yet you are seeing black smoke.

    For the most part, the fuel pressure looks good. In one run the min FP was 34.57031 which is low. Is it low enough to indicate a problem? IDK. Esp if the FP is not chronically low.

    How much boost are your making? Plug gap? Could you be blowing out the spark?

    I am not a tuning expert. And at some point the question has to be asked, didn't you pay for the advice of an expert?
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  11. Don 95Vert

    Don 95Vert Founding Member

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    What you logged is fairly useless for for diagnosing anything at all - when we have people log things for retunes here is the MINIMUM that we require: Ford Datalogging Instructions

    You should beg borrow but not steal a laptop and use the LiveWire as a pass through logger - that way you can log enough things to get useful data. You should log the UPPER CASE PIDs - which are direct memory reads and thus faster.

    Units for the MAF and other things such as TP are generally in AD Counts - a digital representation of voltage. A MAF will peg at 1023 AD counts if the tune was set up right to begin with, if not than the limit is 980 counts.

    Why is the PCM adding fuel even though the car is running rich and you get 02 sensor codes? One reason is exhaust leaks ahead of the 02 sensor - even a pinpoint leak will cause the 02 sensors to read atmospheric 02 and 'think' the A/F mixture is too lean and thus add fuel. Many other reasons - and one right off the bat if lengthening the 02 sensor wires by soldering at home - this totally messes up the function of the 02 sensor and NEVER should be done. The other thing to mention is a severely lean motor will also sometimes smell 'rich' - so you never know until you put a wideband on it.

    Hope this helps.
    Don
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  12. Mystic1350

    Mystic1350 Member

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    DON--- (sorry to jump this thread guys)...
    I have an exhaust leak before the front O2's (driver side) and i am gettin the 1132 and 1152 codes..The leak is definately small
    My question is--- how bad is driving the car while running rich like that??.. i cant fix the leak for a few months however will be driving the car sporadically
    what are your thoughts?
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  13. Don 95Vert

    Don 95Vert Founding Member

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    Fix exhaust leaks. They affect everything -not like an old carb car. In a worst case scenario without a tune fixing it, the PCM will apply fueling changes to WOT. Not good for performance, mileage or plug life.

    To the OP - I'd also look at the fuel rail sensor if this is an electronic returnless car (99-10). We always tell tuning customers with SC's or turbos to carry a spare and a tool to change them, as these often go when subject to boost pressure. Often they will leave you stranded, but can also do wierd things as well.

    Don
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  14. mat82284

    mat82284 Member

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    Thanks guys for all your help. I'm at school right now so i cant respond to all questions. I was waiting for that automatic e-mail reply but I just rechecked the thread to find responses.

    Anyways, I am running about 14psi, but I never actually get that. I rarly ever get into boost honestly. I drive like a normal person somehow. As for that sensor I wish there was a simple way to find out if its bad

    As for exhaust leaks. I double checked everthing after the shop installed it and i didnt hear any ticking sounds. I also didnt extend any 02 sensors. The front 02 sensors are bran new as well. I'm running the BA-2400 maf (if that matters)

    I'll barrow my friends laptop and hope that it logs. Its a vista machine so im not sure if the SCT software will run. I'll try to get a good full log.
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  15. wmburns

    wmburns SN Certified Technician

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    IMO, if the fuel pressure sensor were bad, most likely would show in the fuel pressure data log. If you look at the FP data, it generally looks good. So unless the vacuum reference line to the FP sensor is missing/clogged, the FP sensor should be further down the list to change.

    Just to be certain, the FP vacuum reference line is attached and free. I could see a case if it were not, the FP would be too low.

    The suggestion about an exhaust leak is great (I am embarrased that I didn't think of it).

    Good luck.
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  16. Don 95Vert

    Don 95Vert Founding Member

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    On a returnless fuel system the only thing the PCM controls is pressure drop across the injectors, which should be 39-40ish all the time - it does jump around, but looking at logs, you'll get the picture. Fuel pressure will vary, sometimes a LOT so the PCM can maintain that pressure drop across the injectors. So looking at FP on a returnless car is not the same as looking at FP on a return style fuel system.
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  17. wmburns

    wmburns SN Certified Technician

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    This is very interesting. Can you help me understand the fuel pressure sensor failure modes and how to diagnose? Esp one that at first glance appears to be working.

    For example, does the FP sensor read chronically low? Should it be crossed checked with an external FP guage?

    From your experience does the Fuel pressure in the log file look within acceptable ranges?

    Thanks for your input as this thread has been a learning experience for me.
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  18. Don 95Vert

    Don 95Vert Founding Member

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    MOST of the time when the FRP sensor fails on a blown car, the engine stops and you have to put a new on on, but I have seen them just do weird things to fueling when they fail but the engine still runs - seemingly OK - usually the pressure drop across the injectors goes all over the place or other strange things. I'd suggest logging pressure drop across the injectors - should be under Fuel Pump and RPMs or Engine Speed, should be under Misc and taking it for a drive and see if it is stable.

    Sometimes they are tough to diagnose and the only answer is to replce it - on a blown car you should have a spare ANYWAY because they DO fail and even if this is not the issue, it is insurance to keep you going when it does fail.
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  19. mat82284

    mat82284 Member

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    Sounds good. I'll try and get a full log tonight with one good pull as well. I prefer to do it at night since black smoke tends to come out when floored. I'll keep you updated if I'm able to get the laptop syncing with it tonight.

    Thanks again for all the great advice and helpful info.
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  20. mat82284

    mat82284 Member

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    Ok I made a new log. This time I used alot of pids. I even used pids I knew shouldnt matter but I just wasnt sure. I had a hard time getting the thing to log, took me 30 mins and when I finally did I didnt want to miss anything so I clicked alot.

    Here is the log, if either of you two are willing to look at it id really appreciate it. I also didnt get a chance to do a WOT run, I was stuck in traffic pretty much the whole time I was driving. If the log doesnt show anything I'll do a WOT run tonight.

    I also looked at the log and I am finding "IAT sensor Tempor" reading extremely high! Is that the internal air temperature sensor??

    If so thats got to be my problem, the "IAT sensor tempor" shows an average of 385. If that means 385 degrees no wonder the car is running rich! The air temps should be at most 130. I've never seen over 130 with my intercooled setup. Average was actually 105 on a 90 day. If that sensor means something else then im lost...

    Thanks In advance for your help!!

    http://home.comcast.net/~mathew82284/MustangLogs.zip
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