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!!!*help*!!! Having a weird ignition issue. Need help troubleshooting!!!

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    !!!*help*!!! Having a weird ignition issue. Need help troubleshooting!!!

    Anyone in the area have a 173 ECU that I can use to troubleshoot my stumbling M20 issue?

    When I'm going along and try to go past 4200RPM it hits a brick wall and feels like a rev limiter kicking in. Cruises just fine anywhere under 4k but refuses to go further than 4500rpm. Tried resetting the ECU but it didn't help. Anyone have an idea of what may be wrong?

    I have the miller MAF conversion with the miller chip tuned for 19# injectors and 91oct.

    I would need to swap ECUs and use my chip to run the car. Anyone have some time to help me out?

    Pm me for my number. Thanks!
    Last edited by MPLFoster; 09-18-2015, 07:32 AM.

    form.follows.function IG @mplfoster

    #2
    Originally posted by MPLFoster View Post
    Anyone in the Puyallup/Tacoma area have a 173 ECU that I can use to troubleshoot my stumbling M20 issue?

    When I'm going along and try to go past 4200RPM it hits a brick wall and feels like a rev limiter kicking in. Cruises just fine anywhere under 4k but refuses to go further than 4500rpm. Tried resetting the ECU but it didn't help. Anyone have an idea of what may be wrong?

    I have the miller MAF conversion with the miller chip tuned for 19# injectors and 91oct.

    Could be a lot of things, but the likelihood of it being the ECU is very slim. I'd start at the CPS, check for wheel wobble, and go from there.
    I have the miller too, had the same problem, ended up being the spark plug wires grounded to the valve cover, but only at 5k RPM. Very odd issue, and probably not what you're dealing with.

    One thing that will help, is to tell us if the tach or the gauges go berserk when it happens.
    If yes: DME is losing timing data, or experiencing a power loss
    If No: Problem is unrelated to the Timing data, or DME.


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      #3
      The tach spudders but seems to be in time with the revs. After resetting the car the eco gauge now reads at max mpg but does not move at all. The temp gauges jumps a little which is odd because it has been running on the cool side for over 1000miles even in 115F weather.

      Other than that the other gauges work properly.

      form.follows.function IG @mplfoster

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        #4
        Unhook your battery for 20 minutes and try again. Perhaps some sort of heat soak?
        '72 2002 pickup | '88 M5 | '89 330is | '89 M3 | '01 Z3M | '11 328xi-t

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          #5
          I'll try it. Not sure about heat soak. As I said, it was running cool while I was in southern Arizona. Still having issues as of yet...

          form.follows.function IG @mplfoster

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            #6
            Unhooked the battery. Didn't help. Checked the grounds on the plug wires. Look fine.

            Anyone know of any simple troubleshooting I can do before getting it checked out? It drives fine until 4200rpm so at least I can get around.

            form.follows.function IG @mplfoster

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              #7
              I has... but in NC
              Build Threads:
              Pamela/Bella/Betty/325ix/5-Lug Seta/S60R/Miata ITB/Miata Turbo/Miata VVT/951/325xi-6

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                #8
                I've had that issue before, TPS wasn't adjusted right.
                Build Threads:
                Pamela/Bella/Betty/325ix/5-Lug Seta/S60R/Miata ITB/Miata Turbo/Miata VVT/951/325xi-6

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                  #9
                  I had that issue when the cap and rotor were going bad.
                  Looking carefully at the gap, the end of the rotor was pretty marginal and the contact points on the cap were starting to get carbon fouled. I used a micro file and cleaned those up and it solved the problem long enough to replace the cap and rotor.

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                    #10
                    Cap and rotor were replaced with new Bosch units about 2500mi ago. Plug wires are bav auto with unknown mileage but look good when inspected.

                    I guess I need to test the TPS now? Pretty sure I saw a procedure for that in the Bentley manual. I'll do that and report back. Fortunately I have a new one on me to test with but i think I have to remove the throttle body to replace it.

                    Again if anyone has any more advice it is much appreciated.

                    form.follows.function IG @mplfoster

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                      #11
                      Update! Still having issues. I had a new TPS from when I got the miller MAF kit so I replaced it for good measure. Replaced the CPS as well. Just troubleshot with a working main relay and that's not it either.

                      The car starts up just fine, idles nicely but won't rev freely. It hits a fuel/spark cut at 2200-3000rpm and won't rev any further. Driveability is shit.

                      Don't know where to go from here. Would like to test against a known good 173 ecu for fun.

                      I have the miller MAF kit with a chip tuned for a 173 running 19# injectors. Tried calling miller but they won't pick up or respond to emails.

                      Anyone have any ideas?!

                      form.follows.function IG @mplfoster

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                        #12
                        Swapped the old AFM setup back in, put the ecu back to stock but with my RD chip. Chugged on the 19#injectors but still had the same issue. Seems like an ignition problem but not sure.

                        Here's a video of the problem. I converted back to the Miller MAF setup so it wouldn't bog out with the 19#ers. I don't think the Miller stuff is the problem.

                        Sorry, we couldn’t find that page

                        as it gets warmer it gets worse. Max speed without it bucking around is 47mph.

                        form.follows.function IG @mplfoster

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                          #13
                          Fuel relay and pump tested fine. Changed out the filter with new Bosch unit.

                          Anyone seen this issue before?

                          form.follows.function IG @mplfoster

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                            #14
                            Bump

                            Need help.

                            Just swapped over my buddy's plugs and wires, still has the same problem.

                            This is what has been done so far:

                            TPS
                            CPS
                            Main relay
                            Fuel relay
                            Fuel filter
                            Spark plugs
                            Plug wires
                            Reset ECU
                            Converted MAF back to AFM and back to MAF again.

                            Still stumbles at 2200rpm while cruising. Does anyone have any ideas?! I'll try anything...I need to be in Arizona like last week......

                            form.follows.function IG @mplfoster

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                              #15
                              Things I have not checked out:

                              173 ECU (need a known working one to make sure mine is ok)

                              Fuel pump strainer. Need to pull the pump out far enough to check it.

                              Anything else I should add to the list?

                              form.follows.function IG @mplfoster

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