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Hesitation, 1200 to ~2400 RPM, then *ping.. AHAA?

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  • Hesitation, 1200 to ~2400 RPM, then *ping.. AHAA?

    Apologies for the long post and longer update... scroll past quote for update.
    [quote:39b30]
    I've been getting this problem for awhile,
    but, i just sat out in the parking lot on lunch and watched the following events:
    [*]Cold engine

    Start car..3 or 4 cranks and its running

    Idle settles to 700RPM and is smooth.

    Clutch goes in and gear shifted to first.

    As i start to pull away, it boggs and sputters.
    If i feather the clutch in ~2400RPM i can take off, but if i don't keep the RPMS up, it bogs down again.

    So i sit there (in nuetral) and watch it bog down as i rev slowly between 1200 and ~2400 RPMS
    Exhaust smell is richer and looks cloudier.
    If i quickly rev it, it sounds as if i could make it backfire thru the intake (which has happend before).

    As i watch the temp gauge warm up, the bogging suddenly stops when the temp gauge goes from:

    to


    Car accelerates fine from a stop, no more hesitation.

    What event occurs when the temp goes past the marker on the side.

    The ECU switches a signal from CHTS to O2 or something similar?



    I always thought this issue was due to my faulty AAC/Idle valve, which i recently replaced.
    The engine idles smoother and has a working fast idle, but this temp related bogging issue is
    still there, sometimes worse than others. I think the times that it isn't as bad is when the A/C
    is on during defrost, so the AAC is bumping up the idle, ...maybe?

    I did the FTS/CHTS bypass for awhile, but believe any benifits it provided was being
    thwarted by my faulty AAC valve. I have it back the way it was.

    No related codes generated the last time i checked on the 03/08/07 (had this hesitation issue back then too)


    I'm sure this has been answered here or there in one way or another, but
    i haven't read anything that fits this MO as i have described above.

    Thanks.

    Oh..
    84 Turbo
    FMIC
    modified 3in intake (also match ported, relocated AFM)
    t3/4 turbo (unsure on flavor)
    stock exhaust

    Frell, frell Frell!!...

    So the other night i decide to replace my oil pressure sender with the autometer one for my aftermarket gauge.
    everything goes smooth, disconnect battery, drop starter, replace sensor (with npt/bspt thread adapter)
    reinstall starter, hook up battery, back it out of garage and park it.

    next morning, day 1:
    Starts up, runs for about 15 seconds and sputters and dies.
    Starts up again, same thing.. rpms to about 1200 and slowly goes down to the normal 700rpm idle,
    but it keeps going down and dies a sputtering death.
    Any attempts to rev it cause an occasional backfire and more sputtering.
    After a couple attempts i can get it to barely idle.
    The temp goes to the 3rd notch and then...*poof everything is fine.
    Pull it in the garage.
    Disconnect the AFM and start it, no rpms past 1700, exhaust is noticeably richer. as predicted.
    Put in spare
    AFM, revs fine...scratch head, say wtf a few times and drive 25 miles to work.

    after work, day 1:

    Same issue as in the morning...let it warm up completely.... drive home.
    side effect: spare afm seems to fix acceleration stumble i had been experiencing.

    morning, day 2:
    I figure, I'll try disconnecting the EGR solenoid.
    Start it..same problem as before, it starts and then dies.
    plug EGR back in.

    disconnect vac line to FPR.
    start it.. rpms up a little, but still bogs on rev
    plug vac line back in.
    Idles long enough to reach temp and drives fine...for about 1/4 mile.
    Intermittently, in the middle of traffic, it starts to bog down...wont accelerate very well, backfires
    if i try to rev it. can't easily go above 25mph...

    I turn around and head back home.

    On the way back home...poof* everything is fine again.

    FUCK!!

    say fuck it and try to drive to work...no more problems.

    Just went out on my lunch with a screwdriver and a crescent wrench..

    Starts up, dies.
    read ECU codes:
    (from my worksheet)

    (dunno what code 42 is about..its not in the 84 FSM)

    after reset, no bad codes show.
    ..even after step 5 of "start car" and its barely, barely idling....

    Car warms up and idles, revs fine...
    Shut car off, disconnect negative battery lead.
    Wait about a minute.
    Reconnect battery
    Start car .
    Rough idle and backfire during revs is back again.
    atleast it is idling.
    Lunch is over, and its starting to rain...again.

    If i can get it running/driving, simply by letting it warm up completely and idle for like 10 minutes,
    i'll rerun the codes when i get home.

    WTF is happening here!!
    tonight i will also try:
    connecting my DVM to the 02 sensor and see if the voltage output is screwy.
    search for vac leaks (doubtfull, all hoses are new)
    bypass fuel filter (its only a 1.5years old)
    check output of CHTS, check resistance between it and ECU.
    check stuff under battery to see if i might have knocked anything loose when i pulled the starter (doubtfull).

    Rainy days and shit like this make we wanna sell it and buy a non FI Datsun truck.[/quote:39b30]


    So after work i got to investigating.
    Unplugged the o2 sensor for shits and grins..
    The plug was filled with water.
    fuck.
    best case, replace o2 sensor if the heating circuit fried the sensor circuit.
    worst case, water shorted out circuit anyway and damaged the ECU.
    I think this is it.

    reason...the lights on my autometer o2 gauge always fluctuated in the stoich area, sometimes
    lean. On the drive home (commute from HELL) it stayed in the lean, off the scale. It idled and
    reved a smooth a few times. those were the times that the light unburied itself and read in
    the middle of the lean section. otherwise it was bucking all the way thru traffic, heavy rain and
    hale. Uphills sucked bad.

    Its my fault too.

    I spliced the plug with a 4th wire for my autometer gauge, soldered the wire right to the blade connector.
    well those seals aren't meant for 2 wires, so i made it work. Water leaked right in there. Its been raining
    like a SOB lately and my rear cowl/hood seal is not installed.

    off to get a new sensor.
    GAHHHHHH!!!!!


    84 AE/Shiro #683/Shiro #820/84 Turbo

  • #2
    is there anyone on this forum with a perfect runnin z31?hahaha i dont think mine will ever be where i want it.

    Once i fix something another thing fucks up,i guess its because its just an old car
    87 2by2 na2turbo,AE shell comin soon

    Comment


    • #3
      My guess is once it crosses from one cell in the cold startup (temp based enrichment map) into the next...

      The entire temp enrichment outside of the temp wire in the maf and FTS is based on CHTS signal. So maybe either the signal is incorrect, or the value for enrichment at that temperature is (for one reason or another). It could also be simply when it switches into closed loop.

      Maybe you could test my hair-brained theory by using a switchable resistor box to duplicate the CHTS during warmup. See if you can manually correct it better than the ECU can?

      Comment


      • #4
        Ok, mine does the same thing. But from No bars, to 1 bar. (probably same temp, just guage is reading differently)

        So if it does change over, does that mean the it is in closed loop?

        Terrible idea putting those wheels on...

        Comment


        • #5
          Jason84NA2T wrote: The entire temp enrichment outside of the temp wire in the maf and FTS is based on CHTS signal. So maybe either the signal is incorrect, or the value for enrichment at that temperature is (for one reason or another).
          Or maybe just a faulty temp sensor/harness/wire/connection, so the ECU always thinks the car is already warmed up even when cold?
          Matte Black 86T - Sold

          Comment


          • #6
            Yeah mine does that too. really annoying, but it goes away. It scared me one day, wet pavement and it did that *click* in a tight corner hard enough to break 'um loose. Makes me look like an r_tard who's never driven a stick before. I've been wondering what causes that, I assumed it was something with my goofy fuel setup (88t ecu, 86 injectors, 87na wiring harness and idle controls),
            My beloved Z:1987 2+2 NA2T w/30a swap.
            My black sheep: 88ss parts car (pretty much stripped and gone)
            207k miles and counting. Turbo'd since 155k.

            Comment


            • #7
              my car does the same but it goes away after the fourth bar. I am not really worried because i never drive the car off right after it is started. I alawys wait for the car to reach the operating temperature, even in the summer.

              1988 NA2T
              K & N, 3" Certified Muffler turbo back exhaust, Hallman MBC @ 8 psi, Z33 wheels

              Comment


              • #8
                Some cars do it, some don't. I just got a car in that started doing that recently. I want to say it is a problem with the maf getting a bit old, maybe taking longer to warmup and read correctly. It does not appear to be an o2 or chts issue.
                Chuck Stong
                300+ Parts and Performance owner
                http://www.300-plus.com
                2002 ZCOT president and always active member

                Comment


                • #9
                  Firehawk wrote: Some cars do it, some don't. I just got a car in that started doing that recently. I want to say it is a problem with the maf getting a bit old, maybe taking longer to warmup and read correctly. It does not appear to be an o2 or chts issue.
                  Hmm, I'll try throwing in my other lower mileage maf in and try it out

                  Terrible idea putting those wheels on...

                  Comment


                  • #10
                    I also have this similar problem, but since mine isn't a daily driver, I never really gave it much care......

                    Now as I read through the FSM, I notice this device: Air Regulator. It's not on the list of codes diagnosed by ECU, and it obviously is an outdated device because it's operated by heating up a bimetal. Supposely, it allows additional air during enrichment and shuts off after warm up. But since it bypasses MAF, it really can be a potential problem maker because no matter how hard the MAF is working this piece of 20 years old bimetal just won't help.

                    I'm still a noob, so I don't really know how much effect this air regulator can cause. What do you guys think?
                    Matte Black 86T - Sold

                    Comment


                    • #11
                      simply86T wrote: Now as I read through the FSM, I notice this device: Air Regulator. It's not on the list of codes diagnosed by ECU, and it obviously is an outdated device because it's operated by heating up a bimetal. Supposely, it allows additional air during enrichment and shuts off after warm up. But since it bypasses MAF, it really can be a potential problem maker because no matter how hard the MAF is working this piece of 20 years old bimetal just won't help.
                      It does not bypass the maf.
                      Chuck Stong
                      300+ Parts and Performance owner
                      http://www.300-plus.com
                      2002 ZCOT president and always active member

                      Comment


                      • #12
                        [quote]Firehawk wrote:
                        Originally posted by simply86T
                        Now as I read through the FSM, I notice this device: Air Regulator. It's not on the list of codes diagnosed by ECU, and it obviously is an outdated device because it's operated by heating up a bimetal. Supposely, it allows additional air during enrichment and shuts off after warm up. But since it bypasses MAF, it really can be a potential problem maker because no matter how hard the MAF is working this piece of 20 years old bimetal just won't help.
                        It does not bypass the maf.
                        You are right, it bypasses TB. I'm really a noob, my previous post should be deleted.

                        Will it still cause my starting ability or idle if it fail to open when cold?
                        Matte Black 86T - Sold

                        Comment


                        • #13
                          simply86T wrote: You are right, it bypasses TB. I'm really a noob, my previous post should be deleted.

                          Will it still cause my starting ability or idle if it fail to open when cold?
                          If it does not open, it will not raise the rpm when cold like it is supposed to. The idle will be smoother at higher rpm when cold, until it warms up. If you replace it, you will likely need to replace the rubber hose, too (or at least be very carefull with it) since it is likely hard as a rock.
                          Chuck Stong
                          300+ Parts and Performance owner
                          http://www.300-plus.com
                          2002 ZCOT president and always active member

                          Comment


                          • #14
                            MrwassmanNA2T wrote: Hmm, I'll try throwing in my other lower mileage maf in and try it out
                            I'll do the same whenever i get a chance.
                            My beloved Z:1987 2+2 NA2T w/30a swap.
                            My black sheep: 88ss parts car (pretty much stripped and gone)
                            207k miles and counting. Turbo'd since 155k.

                            Comment


                            • #15
                              *bump
                              update in original post.
                              seems like i'm not the only one.
                              http://www.z31performance.com/forum/...pic.php?t=4391

                              ZMECH - i'll try the clamping of the return line.


                              84 AE/Shiro #683/Shiro #820/84 Turbo

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