Strange hesitation between idle and 3000 rpm

Discussion in 'Mustang Chit Chat' started by xxsurvivalism, Apr 12, 2021.

  1. xxsurvivalism

    xxsurvivalism Member

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    I caught the hesitation while datalogging. This is a warm start, the car had been sitting for maybe 40 minutes before logging this. Started, fuel trims are at a staggering +60 (60% lean). Then the idle drops (which the datalog didn't seem to capture because the tach dropped to like 400 RPM), engine starts choking out and the fuel trims drop all the way to -24 rich while its acting like its going to die. NOT PICTURED: It'll recover, the idle will jump up to 1,200 RPM and both Banks skyrocket back up to 30-40%. This is after Brisk Racing Plugs and a new MAF installed this morning.

    FuelTrim.jpg
     
  2. xxsurvivalism

    xxsurvivalism Member

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    Also datalogged while driving at temperature. Both banks are lean around 20% at idle. Driving under light to moderate load, the banks jump to 40% to 50% lean around 2500-3000 RPM. Then if I decelerate from 3,000 both fuel trim banks zero out. They stay at zero until I begin accelerating again. Don't think it could be a vacuum leak, wouldn't the banks drop towards zero under acceleration or at speed?

    FuelTrim2.jpg
     
  3. xxsurvivalism

    xxsurvivalism Member

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    Starting to think that someone uploaded a canned tune with the MAF installed backwards..... or something. That's all I can think of at this point lol.
     
    06 T-RED S/C GT likes this.
  4. Pentalab

    Pentalab forum member

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    Assume the existing tune is junk. Start from scratch, and get lito to tune it. Just make damn sure everything in there is installed correctly, no vac leaks, and no wiring errors, clogged sock filters, maf sensors installed backwards, unmetered air getting past, exhaust leaks, cams installed correctly, etc, etc.
     
  5. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

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    After replacing the spark plugs and MAF sensor along with ruling out any potential vacuum leaks, wiring errors ect, and yet your car continues to have the same issues via the datalog? Then I agree that your existing tune is garbage and would definitely recommend getting a remote tune from Lito, no question about it.
     
    xxsurvivalism likes this.
  6. xxsurvivalism

    xxsurvivalism Member

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    I really do appreciate the help, fellas. Thank you.
     
  7. GlassTop09

    GlassTop09 Member

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    I was looking at your warm start idle datalog info & it does show that you have an issue w\ the MAF scaling....the datalog shows an inverted MAF scaling pattern vs engine RPM's which is wrong (MAF scaling should be reading opposite of what it is showing vs the engine RPM's) so that is definately off.
    The MAF readings at 900+ RPM's are too low (should be around 8-9 gms/sec instead of the 5.5-5.6 gms/sec shown) so the PCM is not injecting enough fuel so the STFT's are trying to make up for the lean condition then as the engine warms up & the engine RPM's start to drop (slow down) the MAF readings are increasing instead of decreasing....which is wrong....so the PCM is increasing amount of fuel injected so the STFT's are trying to make up for the rich condition (this is where the engine stalling & spitting is occurring) then the scenario reverses itself until the PCM catches back up then once it does you're fine afterwards.

    The B1S1\B2S1 O2 sensors (your feedback system) pattern in this case is indicative of your feed forward system (MAF) being out of scale from the time the MAF comes online (when the engine starts up in OL) until it catches up w\ itself in CL (the LTFT's trim out to match up w\ the O2 sensor feedback to drive the STFT's back to switching thus the AFR is back to 14.7 or stoich) regardless of the actual MAF reading (most likely the PCM has failed the MAF data by then & is using substituted MAF readings even though the MAF sensor itself has passed PCM MAF voltage checks thus no MIL).

    I would suggest as has been mentioned to get the induction side smoke tested along w\ the EVAP system (main part is the CPV & line from CPV to EVAP canister) to definately rule out any unmetered air (or vacuum leaks if preferred) issues before getting retuned but the MAF situation you have is a definate contributor. Also suggest to get the MAF wiring\connections between the MAF sensor & PCM checked for resistance & integrity as well as proper PCM MAF signal reference voltage to MAF sensor since this comes from the PCM itself in addition to the 12v+ & ground to ensure that the MAF wire is getting properly heated up. I would also suggest the next time you graph a start up you graph the B1S1\B2S1 O2 sensor voltage as well to see how fast\slow the O2 sensors are coming online once the PCM switches from OL to CL...especially since you have those BBK LTH's installed (full length)....my read from looking at your data is that they may be slow coming up off 0mv initially (habit of Motorcraft F85F-9G4444-BD O2 sensors you've installed earlier) which can initially drive the STFT's high telling PCM to increase fuel until the O2 sensors voltage finally respond to initially exceed 800mv (this is where the P2195, P2196, P2197, P2198 DTC's will usually come from if the initial O2 sensor voltage response doesn't happen within a specified amount of time after OL to CL switch....) to tell the PCM to start pulling back fuel. This may also need to be addressed in the tune as well.

    Hope this helps.
     
    Bullitt2954 likes this.
  8. xxsurvivalism

    xxsurvivalism Member

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    Helps a TON man, thank you so much. I'll start looking into those 3 things tomorrow. Much appreciated.
     
  9. xxsurvivalism

    xxsurvivalism Member

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    Pulled the cam cover, they are indeed Comp Cams XFI NSR Stage 2. Now that I know that, I can get a tune haha. Was also reading a blog that includes information from Lito. Apparently the Motorcraft O2 sensors (as GlassTop09 had mentioned) are insanely slow, don't heat up well and are basically useless. So I have some NTK 22060's on the way as well as some Ford Performance EV6 24lb high flow injectors. I'll get everything on, datalog again, and get a tune from there and see how it runs.

    IMG_20210511_093426650.jpg
     
  10. xxsurvivalism

    xxsurvivalism Member

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    Question:

    Why would someone install a catless offroad x pipe with long tubes... And have rear 02 sensors? And they are wideband. I didn't even notice them til a few days go. Feel like an idiot. If the downstreams are being pummeled by exhaust that isn't passing through a catalytic converter, would that leave the potential for them to tell the computer to adjust fuel trims?

    IMG_20210517_113551595.jpg

    The car came from California. Maybe it was flashed before I bought it? S&B also "claims" you don't need a tune for the CAI that is on the car.

    But again, with the FRPP intake manifold, 62mm tb, XFI cams, long tubes and catless x pipe with a total of four O2 sensors on the car, wouldn't it throw a bunch of codes if it was flashed and driven? Would it even start?
     
  11. xxsurvivalism

    xxsurvivalism Member

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    Probably should have mentioned I unplugged my EVAP purge valve's power and then the line going to the canister. Put my finger on the purge valve inlet stem and it was still pulling vacuum.

    So if it is stuck open, seems like it would be pulling fumes/air into the intake manifold and creating a lean environment no? I also pulled the purge valve hose connected to the intake manifold and plugged the intake with my finger. Seemed to run a lot better for that moment.

    I'll have a new purge valve on tomorrow morning.
     
  12. GlassTop09

    GlassTop09 Member

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    Ok, now the pieces are coming together. 1st off, the O2 sensor w\ the green sleeve & green connector is actually a NB sensor--not a WB sensor. This green connected O2 sensor is actually a pre-cat NTK 22060 O2 sensor (these used to be Ford OEM pre-cat NB O2 sensor from 1996 thru 2010 MY of S197 production....WB O2 sensors didn't show up on Mustangs until MY 2011 w\ the advent of the Coyote V8) & it should not have been placed there---it is designed for engine feedback control only. The blue connector NB O2 sensor is actually a post-cat NTK 22500 O2 sensor (same as listed in parenthesis above) which are designed to check for the existence of free O2 in exhaust post-cat or mid bed of the OEM cat only....not used for engine feedback control. The element shielding is not the same size thus they use a different sampling size so if these are mixed up as your picture is showing (assuming the same install scenario in the LTH's prior replacement) then yes, the O2 sensor feedback to the engine bank that the blue connected O2 sensor was installed would indeed have been skewed so engine fueling on same bank would also have been skewed. Needs to be fixed.....put the other blue connected O2 sensor in place of the green O2 sensor in the midpipe then install both new NTK 22060 pre-cat NB O2 sensors in the LTH's to rectify this mess. Only the O2 sensors plugged into the green harness connectors (you most likely have O2 sensor extensions plugged into these in order to reach the O2 sensors installed in the LTH's) provide feedback to adjust fuel trims, O2 sensors plugged into the blue harness connectors only check cats & don't have anything to do w\ fuel trim adjustment at all. I would suggest that you make sure that all these are connected properly to the proper harness connectors as laid out here.

    Now as for your other question, this was the status quo that folks did to these cars due to past issues w\ cats back in the day being "flow restrictive" thus power robbing (race car\performance thinking) so SOP was to go w\ an O\R midpipe (no cats) when installing LTH's. The tune was definately flashed before you bought it (among making O2 sensor transport delay setting changes for the full length BBK LTH's, disabling the CMCV's for the FRPP IM, maybe some ETC smoothing for the FRPP 62mm TB & some tuning for the Comp Cams 127200 cams...the rear O2 sensors are most likely also disabled in the tune thus no DTC's for them). This was done in Cali as well also back in the day.... The rear O2 sensors, while not enabled in the tune, do still need to be plugged into the harness as the PCM needs to see the O2 sensor heater 12v+ voltage as well as some sensor output voltage thru them in order to not fail all the O2 sensors. So as long as you've registered your car in a county that doesn't require a smog test passage to get your registration you can leave the midpipe as is.....at this time I should say & leave it at that. If S&B claims that the CAI doesn't need a tune (MAF transfer function change in tune to align MAF airmass values according to the ID of the MAF section in CAI) then you really need to get this car retuned after you fix\straighten out all the other broke stuff.....once you get all the O2 sensor mismatch straightened out & EVAP CPV replaced I would then run datalog again on a full cold start & record all until car reaches full hot idle to see if the MAF readings still follow an inverted pattern (low gms\sec on high RPM's then gms\sec increases as engine warms up & drops RPM's)....if they still do this then get a retune....preferrably from someone like Lito....as this was most likely messed with in the tune after you verify all MAF wiring\voltages are within spec & you've replaced the current MAF sensor w\ an OEM MotorCraft ALFM-131 MAF sensor for your MY Stang (which according to your prior posts you've already done?).

    Now you know why I made this suggestion in my posting......this is 1 of the most overlooked parts of these cars....outside of the gas cap. Yes if these CPV's are stuck open\seat failed you will pull in excessive unmetered air along w\ the canister fumes & create a "vacuum leak" due to drawing air in thru the canister after the canister has no more fuel vapors to add to the air. You also need to test the flex line that connects the EVAP canister to the CPV line at the canister for cracks as well at a minimum....thus why I suggested to do a smoke test on the entire induction system. I'm surprised you haven't gotten any EVAP DTC's as w\ that stuck open CPV the EVAP canister\system can't be tested by the PCM so this is also suspect IMHO. These parts can fail & not immediately set a MIL so it is important to physically check these for proper operation....and especially whenever you suspect a vacuum leak!

    These S197's are getting old enough that all this stuff needs to be gone thru to ensure that all is working properly. I would also suggest that the EVAP canister CVS should also be replaced as well (this valve is used by the PCM to perform EVAP system leak tests)...it is NO (normally open when no power is applied to it) whereas the CPV is NC (normally closed when no power is applied to it)....the CVS seats usually go bad meaning they will work but not fully seat off thus not allow the system to have a vacuum pulled on it when the PCM is trying to run EVAP leakdown tests.

    Hope this helps.
     
    Last edited: May 17, 2021
    xxsurvivalism likes this.
  13. xxsurvivalism

    xxsurvivalism Member

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    Helped a bunch, thank you.

    I put new (and correct) NTK's downstream. Also replaced the CPV. Fired it up to datalog. Initial start was probably the worst it has ever run. It smoothed out somewhat after warm up and the fuel trims seemed to come down a bit. I even saw normal fuel trim numbers (-5 / +5) at idle for a small amount of time! Upon accelerating to 2500/3000RPM, the fuel trims jumped back up to +20/+30. Super interesting. On this cart, it seems as if the maf flow rate is low at idle and increasing under load, as it should? I have a cold start chart from this morning as well, havent looked thrpough it yet but I will shortly.

    DataLog 5_18_21.jpg
     
  14. xxsurvivalism

    xxsurvivalism Member

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    Cold start. Just a peak at it, it goes down 550 lines.

    DataLog 5_18_21COLDSTART.jpg
     
  15. GlassTop09

    GlassTop09 Member

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    Ok, now don't take this the wrong way but I have to bring this up. In your post #50 you show that you understood that "downstream" means the O2 sensor bungs that are located in the BBK midpipe or "post-cat" position.
    You just stated in post #53 above that you installed the new NTK 22060 NB O2 sensors....which are designed for "pre-cat" or "upstream" usage....downstream. So does this mean that you actually installed these new NTK 22060 O2 sensors in the BBK midpipe bungs in the picture you posted in post #50 (which would be the wrong place) or does this not represent what you meant to say that you installed the new NTK's in the bungs in the BBK LTH's so upstream (which would be the correct place) & installed the other old blue connector O2 sensor that was installed in 1 of the BBK LTH's prior, in the BBK midpipe where the green sleeved\connector O2 sensor was? From reading your post #14 you show thru my interpretation of your wording that the same blue\green connected O2 sensor mismatch was installed in the BBK LTH's prior as they were shown installed in the BBK midpipe picture you posted in post #50 so would suggest that you also understand O2 sensor "upstream" position thus purpose.....so which is it?

    Need some clarification here................ Trying to help you but you gotta help us as well.

    Ford made the O2 sensor connectors color coded on these S197's for a reason, this is why I referred to them in post #52................. It is very obvious that the prior owner didn't catch this mistake before you bought the car.

    You do realize that you could've just started out by reinstalling the existing green\blue connected O2 sensors in their proper places (both greens in the LTH's or upstream & both blues in the midpipe or downstream) to see if the O2 sensor issue straightened out before buying anything, correct?

    Just saying.........................

    Now w\ that out of the way, from looking at the datalog of your engine at full hot idle (which is kinda high IMHO for Comp 127200 cams) the MAF readings are still too low vs engine RPM's so is still suspect IMHO. Since you've replaced the defective CPV & assumed tested the new part to ensure that it's good...you've taken this big unmetered air issue out of the picture but I need clarification on the O2 sensor setup before I can go w\ what the STFT\LTFT fuel readings in log says to be sure.

    In the meantime I will suggest to do this concerning the MAF situation:
    Measure the ID of the MAF section in that S&B CAI & see if the ID is 3 3\16" (this is the MAF section ID size of an OEM S197 4.6L CAI as measured by me as I measured mine for informational\testing purposes back in the day...this converts to being 80.9mm or 81mm rounded up)....I got a hunch that the MAF section ID in that S&B CAI is larger than 81mm which would give some explanation to what I'm seeing thru your logs (you'd need to have this info on hand anyway to give to your tuner) assuming that the tune's MAF TF is still set for the OEM CAI.

    Hope this helps.
     
    Last edited: May 19, 2021
  16. xxsurvivalism

    xxsurvivalism Member

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    Upstream o2's are new NTK 22060, Downstreams in the xpipe are new NTK 22500. Ya there was some swapping around of the o2 sensors for datalogging, to see if there were any significant changes. I can see how some of the pics got confusing. Looking back at this whole situation, there's a million different things I could have done different or a bunch of different places I could have started. I'm new to injected computer controlled engines. Everything I've replaced is just peace of mind when I DO actually getting it running right.

    Here are the O2 sensors that were originally on the car when I got it, before trying the Motorcrafts. Top two were upstream, bottom two were downstream.

    IMG_20210518_151019861.jpg
     
    Last edited: May 19, 2021
  17. GlassTop09

    GlassTop09 Member

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    Been redoing some landscaping around the house since my trees have started budding so I can turn on the sprinklers......have moved\spread 72 bags of lava rock so been a little disposed w\ body aches......

    Ok, this clears a lot of stuff up for me so I can understand\follow your thought processes now. Good thing that whoever installed that Bosch LU 4.2 A\F sensor (or W\B as you've identified) prior your ownership installed it in the midpipe (where the rear O2 sensors are disabled in the tune so it wouldn't matter) or that car would've definately had issues (W\B sensors operate differently voltage-wise & would've freaked out this Spanish Oaks PCM....may not have ran). The other upstream NB O2 sensor by the green sleeved NTK appears to be a Bosch 15717 NB O2 sensor (which is the base part for the current Ford OEM F85F-9G4444-BD NB O2 sensors) which most certainly can cause issues, especially during a cold start up to full hot idle due to different operating specs which gives meaning to the adage to always replace these in pairs.......
    Yes there are a million different things along w\ a million different places to start making checks but w\ these computer controlled fuel injected vehicles, when checking issues such as yours, I found it very helpful to always use the Eric O. phrase......."Test, don't guess". So where ever you start in the process, test each part against known operational specs to confirm\fail that part before going on to the next, repeat according to a set process until you either find the offending part OR you've narrowed the issue to the tune files in PCM by eliminating any physical breakage 1st. A lot of these vehicle's subsystems intermesh w\ each other so symptoms can be very similar\identical but point to different suspects depending on the parts involved so keep this in mind as well (example of this is the Misfire Monitor, there are several other items\issues that can cause uneven crankshaft velocity variations outside of an actual plug misfire but most get stuck on this due to the label: misfire...so plugs are always thrown out to check).....this is why it's much better IMHO to do the dirty work of testing\checking each part\component instead to either confirm it's bad or to remove it from consideration.....also to get the proper minimum diagnostic equipment to speed up this process (like a smoke leak detector, scan tool that has some OE bi-directional capability, 4-channel oscilloscope & a good DVOM w\ a good set of back probes....) to take a lot of the guesswork out of this & save you a lot of time in the future.

    The old days of simple systems for DIY'ers are gone. I know most just want a quick fix answer to their issue(s) but w\ these cars that won't be so easy to always provide unless enough diagnostic info is given to rule out other possibilities.

    Now this lets me know the STFT readouts in the last logs are legit so unless there are more vacuum leaks present than what you've ID'd so far (doesn't appear to be from looking at the logs), the tune in the PCM is the last part for you to get addressed as your FP was good & the FPDC was also good so this rules out any fueling issues....your issue is strictly in the feed forward side (MAF) now. After that is done you should be GTG. Don't forget to let your tuner know that you've installed those new FP LU24A fuel injectors so that the injector data can be updated as well. Just cause they're the same 24 lbs\hr rating as your old ones doesn't make them identical........ Been there, done that.

    Hope this helps.
     
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