When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I hate spending so much time explaining what I don't know - but I'm not familiar with Bluedriver's capability and cursory online search didn't completely cure that problem.
But, a monitoring fuel trims while doing a simple hypothetical test can help understand the relationship between STFT & LTFT. (STFT can be likened to a weather vane - shows which direction LTFT is going to be moving if conditions stay as they are.) ie: is the problem still present (at CURRENT RPM / LOAD conditions). The fuel trim 'table' in the PCM is multi-dimensional (at least two dimensions) based on engine RPM & LOAD). /// IF STFT & LTFT were at ZERO, at idle, and you 'create' a small vacuum leak (SAY unhook PCV valve hose)./// STFT will go 'positive' to compensate for the 'unmetered' air being ingested into the combustion process (note this ~number). If you leave it this way for a few minutes, LTFT will grow to be equal to the initial STFT number noted as STFT gradually declines back down to ~ZERO. Along the way - you will have LTFT positive, AND STFT some less positive.
Now if you plug the vacuum line back on, LTFT will still be ~'positive', but STFT will go negative the SAME amount --- sum total being ~ZERO. But LTFT will be positive while STFT is negative, and after a while they will BOTH be ~zero again.
You can verify this with Bluedriver. I emphasized RPM & LOAD because it adds yet another layer to consider. The fuel trim tables are multi-dimensional (at least two dimensions) consisting of fuel trim values at various RPM and LOAD conditions. (It looks something like a Rubics Cube.) A problem CAN be occurring at ONLY certain range of RPMs or LOAD. And Mass Air Flow is a component part of LOAD calculations!!! (more to keep in mind!)
------------------
But, I alo read up on the Innova fuel pressure tester and - from what I see, it's reading is "RELATIVE" to 'atmospheric' pressure. Your injector nozzle is at the valve port (I think, like my '04) and is at 'MINUS' IM vacuum relative to 'atmospheric' so vacuum amount (21 in-hg = 10.3 psi) must be added to your readings. I went back to post # six and I note that your fuel pressure readings look pretty OK: The fuel pressure regulator AND FICM must be working OK.
I'm guessing your injectors are probably rated at 39 or 40 psi (as my '04) and the system seems to be maintaining that across RPM (& Load??) range.
--------------------
I know @Steve83 po-po's the idea of that 'injectors' can get curded up --- (but if the Fuel Rail, fuel lines, fuel filter has been off / opened up and ANY junk gets in there - it AINT GONNA pass through them little bitty holes in the injectors. And the result of that would certainly show up quick in the fuel trims. (More at higher RPM --- IDK, maybe). The only other thing that strikes me is O2 sensors. (I recommend you replace them -ANYWAY). I believe clogged CATS would exhibit the opposite effect and drive fuel trims negative (because trapped inert gasses in the exhaust makes exhaust more oxygen deficient, making O2 sensor voltage outputs higher - shortening fuel trims at higher RPMs.... IMO.)
Just my 2cents for you to ponder.
More helpful info from you F150Torqued thanks.
Ive tried uploading pics of my live data and freeze frame on here but they just disapear so i have no idea what im doing wrong.
I did go to live data and check out my o2 voltage and think you may be on to something with them. The numbers are as follows;
So if I read that right, it looks like B1S2 is being lazy at idle and at 2000 rpm but more normal under load (strange). So that could be a possibility (bad o2). I do have one aftermarket o2 sensor so i think i'll try it this weekend and just see if anything changes.
I have heard that you should stick with Bosch o2 sensors, any feedback?
So if I read that right, it looks like B1S2 is being lazy at idle and at 2000 rpm but more normal under load (strange). So that could be a possibility (bad o2). I do have one aftermarket o2 sensor so i think i'll try it this weekend and just see if anything changes.
I have heard that you should stick with Bosch o2 sensors, any feedback?
OK 'hold on there' - I've gotta grab you by the belt loop and slow you down just a little to keep you on track! (Not scolding you).
Your DOWNSTREAM O2 sensors have ZERO effect on fuel trims. Focus on and concentrate on the UPSTREAM O2's _only_ with respect to fuel trims. They are the one and only thing that drives fuel trims.
The REAR (downstream) O2 sensors are strictly for monitoring catalyst efficiency, and require the CAT to be completely up to temperature (Inferred Mid-Bed Temperature ~ 1000 to 1200º f) before the aft sensor readings mean much. The PCM compares the 'RATIO' of voltage switching between the front and rear O2 sensors to determine if the CAT is doing its job (burning off any unburned hydrocarbons). What you referred to as 'llooks like B1S2 is being azy' is what you want for REAR O2s. The PCM CAT Status Monitor will trigger a P0420 or P0430 code if the switching ratio of REAR O2s _exceeds_ ~70% (depending on exhaust configuration). So you want the rear ones flat or quieter than the front ones ---- AFTER they have reached operating temp.
Far the best way to view and assess O2 sensor operation is with a Graph Screen. If you can do so with Bluedriver, I would recommend it. Here is a screenshot of the dashboard I have set up on Torque Pro for this purpose. This shot was taken at light cruise ~40 mph. Rear O2 are not ALWAYS that smooth (such as cold, accelerating, or under load. On fuel OPEN LOOP acceleration, they will flat-line @ .9 v. Fuel shutoff deceleration, they will flat-line at ZERO v.)
Front & Rear O2 sensors at light, no load, cruise.
Here is a screenshot of upstream O2 sensors and their relationship to fuel trims. I prefer fuel trims displayed on '+' and '-' swinging half gauges. It is much too hard to watch digital numbers jumping around.
Bosch O2 sensors (or one of several aftermarket ones) should be fine.
Last edited by F150Torqued; 06-15-2018 at 11:18 AM.
Bosch is the OEM for Ford oxygen sensors. But that does NOT mean that all Bosch HO2Ss are the same quality. Just like Ford made the Taurus & the Fiesta, Bosch makes high-end parts & low-end parts. If you want the best sensors, buy the ones that have to meet Ford specs: the ones in Ford or MotorCraft packaging.
But I DON'T think you should be throwing part$ at this. FOLLOW THE DIAGNOSTIC PROCEDURE TO THE LETTER.
OK 'hold on there' - I've gotta grab you by the belt loop and slow you down just a little to keep you on track! (Not scolding you).
Your DOWNSTREAM O2 sensors have ZERO effect on fuel trims. Focus on and concentrate on the UPSTREAM O2's _only_ with respect to fuel trims. They are the one and only thing that drives fuel trims.
The REAR (downstream) O2 sensors are strictly for monitoring catalyst efficiency, and require the CAT to be completely up to temperature (Inferred Mid-Bed Temperature ~ 1000 to 1200º f) before the aft sensor readings mean much. The PCM compares the 'RATIO' of voltage switching between the front and rear O2 sensors to determine if the CAT is doing its job (burning off any unburned hydrocarbons). What you referred to as 'llooks like B1S2 is being azy' is what you want for REAR O2s. The PCM CAT Status Monitor will trigger a P0420 or P0430 code if the switching ratio of REAR O2s _exceeds_ ~70% (depending on exhaust configuration). So you want the rear ones flat or quieter than the front ones ---- AFTER they have reached operating temp.
Far the best way to view and assess O2 sensor operation is with a Graph Screen. If you can do so with Bluedriver, I would recommend it. Here is a screenshot of the dashboard I have set up on Torque Pro for this purpose. This shot was taken at light cruise ~40 mph. Rear O2 are not ALWAYS that smooth (such as cold, accelerating, or under load. On fuel OPEN LOOP acceleration, they will flat-line @ .9 v. Fuel shutoff deceleration, they will flat-line at ZERO v.)
Front & Rear O2 sensors at light, no load, cruise.
Here is a screenshot of upstream O2 sensors and their relationship to fuel trims. I prefer fuel trims displayed on '+' and '-' swinging half gauges. It is much too hard to watch digital numbers jumping around.
Bosch O2 sensors (or one of several aftermarket ones) should be fine.
Ok. On my BlueDriver live data, I too am looking at a bar graph, the numbers i displayed were just the minimum and maximum voltage for each one. My bar graph has min and max like yours does on the gauges. As I compare my data to yours, my upstream sensors look very similar to yours with a rapid up and down motion at varying rpm and under load. But as rpm increases the rapid up and down motion, (although still rapid) stretches out.
Is that right (normal)?
As for downstream sensors (i get it nothing to do with fuel trims) my bank 2 sensor 2 has a slight up and down motion (Ripple) and over time a slow wave effect all at the same time, whereas my bank 1 sensor is absolutely flatlined as if looking at a heart monitor that is not attached to anyone.
Shouldnt both downstream sensors be doing the same thing ?
Is that normal?
If i ever figure out how to post pics theres going to be a bunch lol.
DISCLAIMER: I'm not a mechanic - and don't even play one on these Forums. My experience is limited to keeping my own vehicles going all my life (most of them way up in years and miles). And my '04 5.4L Triton is quiet different from yours. [_] Check this box if you agree with this disclaimer!. LOL
Ok, having said that - I _HAVE_ learned some about OBD in my short life. OBDII readings (or DTCs) SELDOM tells you what's wrong by any one specific reading, and many times with multiple readings --- other than by a process of elimination coupled with some creative mental gymnastics.
After reviewing your prior diagnostic readings and posts, AND studying your Bluedriver screens --- something emerges that COULD explain your bad fuel trims.
Your O2 sensor graphs look normal. Switching rate decreasing when RPM and/or LOAD increases is normal. It is a little difficult to wrap your head around this, but if the PCM's adaptive corrections are working properly - the O2 sensor signals _SHOULD_ continue to look normal. What P0171 and P0174 simply says is that the PCM has reached its adaptive limit trying to keeping Fuel/Air ratio proper. The 'LENGTH' of each injector pulse cannot be directly witnessed in the O2 switching signal, only in fuel trims. This all tells me the condition is NOT MAJOR OR CATASTROPHIC, because the PCM has managed to _marginally_ correct for it VIA fuel trims - as per design intent.
Your fuel pressure readings are normal and track OK from idle to increased RPM / LOAD. O2 sensors appear to be functioning fine per graphs / readings. (You might look at Mode $06 report and it 'SHOULD' show what the RMS (or average) voltage is. Should be VERY close to .45 volt. But I do not suspect any problem there).
ASSUMING - the usual cause of Positive Fuel Trims is generally unmetered air, ie: vacuum leak - OR exhaust leak upstream of the O2 sensor -- as noted by @Zeeduke in post #18 (Whom I quoted a little negatively in Post #20). It is 'interesting NOW to NOTE the difference between fuel trims at idle (which has consistently been slightly _negative_ ///as though correcting for a positive condition///. And at 1500-2000 'no-load' condition VERY positive, then under HIGHER RPM or under load - being slighty less _positive_)
THERE IS something else that is happening at that point (light load, mid-range RPM). The PCM will be commanding some EGR (varying downward as load increases). Thus - IF there was an air leak in the EGR exhaust gasses recirculation path (??? see disclaimer)- it would introduce 'unmetered' air (oxygen) in the exhaust ahead of the O2 sensor - WHEN the EGR valve opens. AND it would be 'purportionately' less as EGR was decreased due to increased engine Load - OR A 'DECREASE' in IM Vacuum due to increased LOAD. I notice in Post #1 that you replaced the 'EGR Tube'. ((my truck don't have one so I am unfamiliar with the 'bizzare looking' contraption. But an air lean in the exahust gasses recirculation path would replicate your symptoms exactly.
You did not mention replacing the EGR valve. And I do not know what the symptoms of a leak in the EGR diaphram would be. But a leak in ANY point between exhaust gas recirculation PATH and atmospheric air would replicate your present symptoms exactly.
I am a STRONG advocate of challenging sensors, or changing conditions to witness OBDII reaction! I would recommend you disconnect EGR vacuum hose and 'plug' it, or disconnect any electrical 'control' to the EGR system and (understanding it will result in a different DTC) see if THAT makes any difference in the fuel trim test results between idle and elevated RPM and/or LOAD.
I also note you replaced the Exhaust Manifold(s) / gaskets. I suppose, but IDK enough about EGR on your truck to suggest if THAT would replicate your symptoms. It _WOULD_ on mine because EGR is accomplished by retarding the cams which would suck air directly into exhaust manifold port ahead of O2 sensors.
The trim numbers reported result from the MAF sensor value, the O2 sensor reading, and the injector open durations, compared to a table of expected values. Your idle trims are all negative, both short trims and long trims, which would mean that the O2 sensors are seeing less air than expected (the MAF sensor reading) or more fuel than expected (the injector open times). It's hard to see that your injectors could let more fuel out at low durations, and less fuel at high durations. That leaves the MAFS. It's looking more like your MAFS readings are off. The MAFS output is the most important part of the equation. You might recheck what's happening in that area.
Here's a thought that I had earlier and just realized it might be reasonable. A hole in the tube between the throttle body plate and the MAFS. It would see more vacuum at high RPM, sucking in more unmetered air as RPM increase, which is what your trim numbers show. I had discounted it before because I was thinking of vacuum in the manifold, which gets higher at idle.
This might involve the PCV system too, since one of the valve cover breather hoses has a port directly in to the that intake tube. A bad valve cover gasket or any crank case seal could let air in to that tube. Even a bad oil fill cap, I think. Maybe you need a new oil fill cap, not a gas cap.
Please consider my comments for discussion purposes ONLY and nothing more.
Originally Posted by BareBonesXL
...
Your idle trims are all negative, both short trims and long trims, which would mean that the O2 sensors are seeing less air than expected (the MAF sensor reading) or more fuel than expected (the injector open times)
But MAF output to the PCM is a component part of Idle Air Control, and Engine LOAD calculations. I don't think it is "INTEMENTLY" involved in calculating or adjusting Short term fuel trims. THAT is strictly a function of whether there is ANY Oxygen remaining in the exhaust stream POST actual combustion process.
Concede - MAF controls Idle speed, and thus the amount of air ingestion, and thus VOLUME of exhaust passing the O2 sensor. But the RPM should put trims in a different fuel trim table and air/fuel mixture should remain 'relatively unchanged'. SO.... if Idle MAF volume is 'abnormal' - could idle air control and Idle RPM remain normal?
Bluedriver should show Idle MAF flow in grams/sec. Should be around 5.8 g/s to perhaps 6.5 g/s. That sensor can be challanged by slapping your hand over the air intake with a variable gap between fingers while monitoring MAF g/s.
Another OBD sensor challenge that hasn't been mentioned that could be beneficial here ... One of my favorite methods of finding vacuum leaks (even on Valve Cover gaskets / IM gaskets, Oil Filler Cap, etc) is to monitor STFT1 AND STFT2 while blowing an _UNLIT_ propane torch around all possible vacuum leak points and/or hoses. I have used this technique, and if you doubt it --- just blow a small whiff in front of the air intake and watch Short Term Fuel Trims go NEGATIVE AS HELL real quick.
Last edited by F150Torqued; 06-16-2018 at 11:01 PM.
Reason: clarification "Idle MAF volume' is ABNORMAL
IACV controls idle speed. The O2 values control injector open duration. The MAF reading with the injector open durations give the trim values.
His trims are way out of whack which is a sign of a funked up MAF reading. Either because the MAF itself is messed up or the air flow around it is.
Even a loose intake hose at the throttle body could cause the high trims at higher RPM.
But. What's really odd is that short trim plus long is negative at idle. That should not happen unless extra fuel, like gasoline or oil, is burning, or if the MAF is not correctly measuring the amount of air.
Notice that things are only "lean", huge positive trim numbers, at 1562 RPM. At 2069 RPM they look pretty normal. At 729 RPM they're all negative, or "rich". So, as soon as the throttle is cracked a bunch of unmetered air shows up. At higher RPM, 2069, the "leak" is smaller, relative to total air. Maybe that's a clue. What could cause a vacuum leak just by cracking open the throttle? Maybe a ported vacuum source is open to atmosphere? EGR often uses a ported vacuum source. Ported vacuum is typically a small hole, just meant for use as a reference or actuator. Other things do too, but I don't know that level on these EFI systems.
06-15-2018, 02:30 AM
- I've gotta grab you by the belt loop and slow you down just a little to keep you on track! (Not scolding you).
