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Thread: AE pulsing in DFCO

  1. #1
    Fuel Injected! JeepsAndGuns's Avatar
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    AE pulsing in DFCO

    16197427, $0D, AMC/Jeep 401 MPFI.

    Ok, so lately I have been getting some random backfiring out the exhaust when decelerating (DFCO) It started out a few months ago and has been getting worse. I can not remember exactly when it started and what/if any changes I made to the bin when it started. I dont remember because it started out weakly, just every once in a while, then it would only do it when cooler, and stop once it was fully warmed up. Now its doing it all the time.
    I couldnt figure it out, why it was doing this in DFCO. Only thing I could think was fuel had to be getting into the engine in DFCO. I was fearing a leaky injector. But before that I decided to do a data log, and low and behold, AE was pulsing rapidly when in DFCO!?!?! You can see it going on-off-on-off and the injector BPW going from 0 to 1.69 and back to 0 as the AE pulses. I am at a loss of what could be causing this. Should it not be disabled in DFCO?
    Only thing I have been making any change to is TPS AE and a little to the MAP AE. With it doing it more when not fully warmed up, I thought maybe it was a MAT/AE correction issue, so I disabled it in the bin and set all the MAT parameters back to what it was stock in the bin (no IAT from the factory in this bin) This did not make a difference. I have tried changing the 0 TPS cell in the TPS AE table to 0 and lowering the lower TPS values a bit. This did not help either.

    I have changed the AE settings in this bin as it has never been enough. For the life of me I can not get the AE to be right. It seems like the more I raise it, the better it does and no more lean spike if I hit the gas, but if I blip the throttle at idle it almost floods it. The backfiring seems to get worse too. AE has been the one thing since day one on this conversion that I have not been able to sort out. Its driving me nuts.
    Anyone have any idea why it would be pulsing in DFCO?

    Attached is a copy of my bin and a short data log showing the issue.
    Attached Files Attached Files
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  2. #2
    Fuel Injected! PJG1173's Avatar
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    I was playing with DE trying to get rid of that same issue when I blip the throttle. the higher % of fuel I pulled out with DE it would pop. when I blip the throttle I only get a little DE no DFCO though. looking at your log I find it weird that you are getting DE and DFCO at the same time.
    87 4Runner, 15" spring lift, 3" body, chevy vortec 355, 5.29 gears, 38.5x15.5x15" Boggers, 280hr, 16168625 running $0D
    93 S10, 36x12.5x15 TSL's, custom turbo headers, 266HR cam, p&p vortec heads, $0D Marine MPFI with 8psi boost.
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  3. #3
    Fuel Injected! 84Elky's Avatar
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    Have been analyzing AE in AUJP $8d, so this is of some interest. Admittedly, not overly knowledgeable of $0d, but some fundamentals are common across all code masks. Some observations and thoughts:
    • In $8d and other masks, the following occurs with Decel Enleamnemt (DE) and DFCO. When TPS% goes to 0 from some significantly higher value, DE is first invoked as PW begins to drop to zero. This occurs rapidly (as it does in your log extract below). But then DFCO begins when PW = 0. Your log shows both DE and DFCO occurring simultaneously. That may be the norm with $0d, but unknown without tracing the code hack.


    TPS IAC BPW MAP
    Sample # Secs RPM % Steps MPH AE mSec DE DFCO kPa
    327 54.955 2450 13 150 58 2.73 46.88
    328 55.119 2450 13 150 59 2.81 46.15
    329 55.283 2400 12 150 58 2.61 45.41
    330 55.446 2450 10 150 58 2.37 41.35
    331 55.631 2475 9 150 59 2.20 39.14
    332 55.795 2450 9 150 58 2.12 39.14
    333 55.959 2425 9 150 58 2.08 38.03
    334 56.123 2450 6 150 58 1.72 34.71
    335 56.287 2425 3 150 58 2.59 28.07
    336 56.451 2450 150 58 2.01 23.27
    337 56.615 2425 150 58 2.08 23.27
    338 56.779 2400 150 57 0.00 YES YES 23.27
    339 56.943 2425 150 57 1.69 YES YES 24.74
    340 57.128 2375 150 87 0.00 YES YES 24.38
    341 57.292 2425 150 64 YES 1.69 YES YES 24.74
    342 57.456 2350 150 58 0.00 YES YES 24.38
    343 57.62 2375 150 57 YES 1.69 YES YES 25.11
    344 57.784 2375 150 56 YES 0.00 YES YES 25.48
    345 57.948 2375 150 56 0.00 YES YES 24.01
    346 58.112 2325 150 56 YES 1.69 YES YES 25.11
    347 58.276 2350 150 55 0.00 YES YES 23.27
    348 58.44 2300 150 56 YES 1.69 YES YES 25.11
    349 58.625 2300 150 55 0.00 YES YES 24.38
    350 58.789 2300 150 55 YES 1.69 YES YES 25.48
    351 58.953 2300 150 55 0.00 YES YES 24.74
    352 59.117 2300 150 55 1.69 YES YES 24.74
    353 59.281 2300 150 55 YES 0.00 YES YES 25.85
    354 59.445 2275 150 54 0.00 YES YES 22.53
    355 59.608 2300 150 54 YES 1.69 YES YES 25.85
    356 59.772 2225 150 54 YES 0.00 YES YES 24.74
    357 59.957 2250 150 53 YES 1.69 YES YES 25.48
    358 60.121 2250 150 54 0.00 YES YES 24.74
    359 60.285 2250 150 54 YES 1.69 YES YES 25.11


    • In your bin, the following tables are both all zero:

    Decel enlean PW reduction .vs. delta MAP
    Decel enlean PW reduction .vs. delta TPS
    The code hack I have shows those tables to be non-zero ("OD PFI update.zip" here: http://www.gearhead-efi.com/Fuel-Inj...Information-OD). Perhaps that is somehow contributing to PW not being zero when DFCO is enabled if in fact DE and DFCO do occur together in $0d

    • Most importantly, the bit that indicates AE is active is (L003D b6 = Byte Offset 19 in the DDS as reported in the TPro Log). That bit is set only when L0005 b7 is set. L0005 b7 is set any time L0261=AE Fuel Mass is > $05 as shown in the code segment below. That would indicate some sensor is telling the code to calcualte an AE Fuel Mass (L0261) believed to be needed, that fuel is in excess of the $05 threshold and therefore AE is flagged as active. Can it be that the MAF sensor is not reporting correctly? Here's the $0d code:


    Code:
    LSAE08 STAA L0261              ;Save it, AE fuelmass
                CMPA L48B5             ; $05 = Fuelmass threshold to flag AE as being active
                BLO   LSAE09           ;Bra if fuelmass < threshold to flag AE as being active [Set AE NOT Active]
                BSET L0005,#$80  ;Status word, set b7, AE in effect
                BRA   LSAE10           ; Bra to continue
    LSAE09 BCLR L0005,#$80     ;Clear b7, AE not active
    and then later, if L0005 b7 is set, L003D b6 is set:

    Code:
    ;-Check for sync. AE
               BRSET L0005,#$80,L822F ;Status word, bra if b6==1, AE in effect   
    ;
    ;-No AE needed here
    ;
               BRA     L8247   ;Bra to continue
    ;   
    ;-Flag AE and lock INT for AE active
    ;          
    L822F      BSET    L006E,#$08  ;Status word, set b3, AE in effect
               BSET    L003D,#$40  ;Status word, set b6, AE active
    Finally, the 1.69ms PW consistently shown indicates a constant anomaly. With all the factors determining PW, it would be rare indeed to get a repeatable PW.

    Two other PW observations from the log indicating something is not right, possibly with a sensor:
    • 1.69ms PW is lower than the lowest PW encountered during idle (not shown)
    • When DFCO is completed at sample 422 below, RPM increases from 950 to 2250 whereupon DFCO is again entered -- but all this happens at 0 TPS% but increasing IAC counts. Something clearly not right.


    TPS IAC BPW MAP
    Sample # Secs RPM % Steps MPH AE mSec DE DFCO kPa
    419 70.342 1625 0 111 53 0 YES YES 25.85
    420 70.527 1375 0 104 47 YES 1.69 YES YES 28.07
    421 70.691 1150 0 99 41 YES 1.69 YES YES 31.76
    422 70.855 950 0 96 40 YES 2.11 38.4
    423 71.019 1125 0 96 40 YES 1.89 36.55
    424 71.204 1150 0 94 40 1.68 32.86
    425 71.368 1100 0 94 40 1.62 33.23
    426 71.532 1075 0 91 39 1.65 33.6
    427 71.695 1025 0 90 39 YES 1.74 35.45
    428 71.882 1025 0 89 39 YES 1.8 36.18
    429 72.045 1175 0 86 39 1.59 33.6
    430 72.209 1400 0 86 39 2.62 28.07
    431 72.373 1600 0 84 39 2.27 24.74
    432 72.537 1825 0 84 38 1.89 22.53
    433 72.722 2050 0 81 37 1.69 YES YES 21.79
    434 72.886 2225 0 106 36 0 YES YES 22.9
    435 73.05 2425 0 132 35 YES 1.69 YES YES 24.01
    436 73.214 2525 0 138 35 0 YES YES 23.27

  4. #4
    Fuel Injected! JeepsAndGuns's Avatar
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    Guess I should have mentioned I have a manual transmission. So I think the point where you see rpm go from 950 to 2200 with no TPS increase is when I downshifted.

    I also see you mentioned the MAF. This is speed density system, I do not have a MAF sensor.

    I do not think (do not remember anyways) ever changing any DE settings in the bin. Only thing I have really fooled around with in the last few months is AE. So it has to be something with the AE settings I changed. I am about to change all the AE settings back to stock and start over.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  5. #5
    Fuel Injected! 84Elky's Avatar
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    Understand SD, and manual trans makes sense. Sorry for assumptions otherwise. But SD or MAF, there is clearly something causing the calculation of the apparent incorrect 1.69ms PW. I'd also check the DE tables against a stock $0d because your's appear to be zero.

  6. #6
    RIP EagleMark's Avatar
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    That was some good code lookup work 84Elky!

    I wonder if the unusual PW number of 1.69 is from "DFCO Additional AE" = "Tips: Maximum Time after exiting DFCO to sustain additional AE specified at L4935 "DFCO Additional AE". We've talked about the additional shot when exiting DFCO before and it looks to be tied into AE in this mask.

    Looks like enough changes were made somewhere that it is on the verge or in the Hysteresis of exiting DFCO when this is happening?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
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  7. #7
    Fuel Injected! 84Elky's Avatar
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    Quote Originally Posted by EagleMark View Post
    That was some good code lookup work 84Elky!

    I wonder if the unusual PW number of 1.69 is from "DFCO Additional AE" = "Tips: Maximum Time after exiting DFCO to sustain additional AE specified at L4935 "DFCO Additional AE". We've talked about the additional shot when exiting DFCO before and it looks to be tied into AE in this mask.

    Looks like enough changes were made somewhere that it is on the verge or in the Hysteresis of exiting DFCO when this is happening?
    Thanks Mark. In the hack I have (re: link in Post #3), L4935 is marked "Not used". And that seems correct as it is declared = 0 and is not found in the code:
    L4935 FDB 0 ;Not used

    PW is defined in the code in a few spots:
    Code:
                CPD     #$0100          ;3907 usecs
    LAIF09      CPD     #256            ;3.9 msec
                LDAB    #32             ;488 usec bias for lookup
    So with the above, can calculate a PW factor for 1.69ms as110d = $6e as follows:
    Given 256d * X = 3.90ms or 32d * X = 0.488ms
    X = 3.90ms / 256 = 0.01523 or 0.488 / 32 = 0.01525

    And:
    1.69ms / 0.01523 = 110d $6e

    Found nothing even close in a PW related declaration or table, so the 1.69ms seems to be the result of a calculation as you also eluded to. It has to be something weird though becuase again, getting the same value everytime is just not possible in the real world.

  8. #8
    Fuel Injected! JeepsAndGuns's Avatar
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    It should be well within the range for DFCO to be active. I have it set to not exit untill 1000 rpm, and must be going faster than 15mph.
    I'll be honost, once you start getting into code, it gets a little above my head.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  9. #9
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    you might have a corrupt bin, it is reporting the same map[kpa] at 2200 rpms as 1600. or a map sensor that has a little oil in it.
    Last edited by ony; 02-19-2014 at 04:48 AM. Reason: more info

  10. #10
    Fuel Injected! JeepsAndGuns's Avatar
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    Ok, so I fooled around with it some yesterday. I decided to start new with all AE settings.
    In the past, I have tried stock 5.7 settings (which were too little) and copied in stock 7.4 settings (wich were almost too much) But this was also back when I was running 10* of inital advance. I have since changed it to 0* like the bin had stock and so many things changed when I did that. Most all for the better, except AE suddenly became too little. I was running a slightly modded 5.7 settings. Ever since the change to 0* base timing I have been trying to get AE working good, but not much luck, thats also when this issue started popping up.
    So I decide to try again with the 7.4 settings and start fresh. So I copied in every single AE settings from a 7.4 bin and gave it a try. No more backfiring in DFCO and/or AE pulsing. But it was still too little AE. I have tried tweeking a few parameters and tables and got it a little better, but still not perfect. As I raise AE and get better running, it gets to where if I touch the throttle at idle it go super rich.
    AE has been the one thing with this swap I have not been able to sort out. It drives me nuts!
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  11. #11
    RIP EagleMark's Avatar
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    IIRC I started with 4.3L CPI settings and then just added some AE and it was like normal tuning...

    There's a lot of little tuning glitches with this TBI to MPFI conversion... when your picky and want it right, like cold start and hot start too!

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
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  12. #12
    Fuel Injected! JeepsAndGuns's Avatar
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    Yea, a lot of it probably is the tbi to mpfi switch, since the pcm and bin were never ment to run mpfi, so things are going to be off, and probably will never be perfect.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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