Jump to content
SAU Community

Constant Misfire That Has Turned Into More..

Josh

By Josh,
in Engines & Forced Induction

 Share

Recommended Posts

Josh Grand Master

Josh

Posted
Posted

Ok, here is my problem, I have an R34 GTT sedan with an R32 RB26 in it, controlled by a ViPec Plug and Play, has run fine like that for over twelve months, a while back I had an issue with the ECM staying constantly powered - draining my battery all the time, which turned out to be a failed Mosfet unit in the ECM itself, I solved that problem by putting a manual switch in the supply voltage line for the ECM power relay, as opposed to shelling out for a new ECM.

Now it has developed a misfire, It happens at all RPM/Load/Regardless of temp/Fuel level in tank. I changed plugs (Partly cos it was about time to anyway), all looked good when they came out. Unplugged coils until I isolated where the issue lay, No. 6 Cylinder, Swapped coils around to see if No.6 was faulty - Nope, coil ran fine on another cylinder and 6 still missed, checked actual spark to the cylinder - was exactly the same as all the others. Checked injectors, swapped No. 6 out - no difference, the injector from 6 ran fine in another cylinder and 6 still missed.

I unplugged the injectors one at a time to check the voltage across the plug while running (Not sure of actual spec, and I will add the car had no problems starting or running besides the miss at this point), all got, I think from memory, 0.3V, but No. 6 got nothing, So now I'm fairly convinced this miss is being caused by something further up the harness than the Injector. Checked from the ECM injector pins in the plug to ground, while running, all but number 6 got 0.6V, Number 6 got 12.5V...... Again I'm not sure what the spec is exactly, but the fact all got 0.6v and the only cylinder missing got 12.5v is a pretty clear indicator the problem is definitely Injector related.. but not necessarily with the injector.. Also I began to think of perhaps an open circuit in that injectors wiring or high resistance.

I also checked the ballast resistor and nearby wiring (due to the fact it runs through the LH wheel arch), No obvious breaks or abrasions to the wire, I checked the resistance through the common wire and each pin in the resistor and got ~6.7ohms for each of them (Which I read on another thread on here that is about normal for them). So I don't think the resistor is the issue.. The only thing I haven't been able to check is actual continuity from the resistor to the injector, and from the injector to the ECM due to shitty length of Multimeter cables and only having one set of hands hah.

So I find the resistor ok and go to start the car, no good, battery has gone flat.. This is where it gets even more Poo shaped... Hook the car up to jumper cables and charge for a bit, turn ignition on, fuel pump primes no worries, turn manual ECM switch on and the brown ECM relay does nothing but click about once a second.... I change out the relay, same problem.. I make sure the voltage is ok and see if engine will turn over - it does, and not sluggishly either - cranks like a pro...

And this is where I've got to now.. a bit stumped... Given the history I had with the failed Mosfet unit before and how the ECM is behaving now, I'm leaning towards saying IT is the cause of my miss, The different voltage to Injector 6 and now the failure to start/clicking relay problem is making me think its shagged.. The fact that everything else I've checked has turned out ok, which pretty much eliminates them as the cause.. Like I said before the only thing I haven't checked is continuity from resistor to injector and injector to ecm, which could show an open circuit, short, or high resistance at least..

Thoughts/Ideas anyone??

GTSBoy Grand Master

GTSBoy

Posted
Posted

Yup. Something bad in that ECU. The ECU triggers the injectors by switching on transistors to earth the injectors. Given it has a history of losing one mosfet already, you'd have to be suspicious of it doing it again. Can you borrow an RB26 ECU and try that. It may not run the engine, but you should be able to see if it triggers the injector. But before you do that, do check the wiring properly. If you need longer multimeter leads, just roll out some extra wire around the outside of the car to get the length you need.

kitto Mentor

kitto

Posted
Posted

Sounds like the ECU has completely fried. Odd that you've had the power input transistor fail, then an injector transistor, and now the ECCS relay grounding transistor/control circuit start failing.

Yes power transistors that drive injectors do fail and have before on RB's. Not uncommon. Open up your ECU and have a look and see if there is burning on the ECU, possibly in more than one location.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • 04-LOOX
      R34 GTR Vspec Garage Sale - All must go!

      By 04-LOOX · Posted

      Hi, is the HKS  Tower Bar still available ? negotiable ? 🤔
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      From there, it is really just test and assemble. Plug the adapter cables from the unit into the back of the screen, then the other side to the car harness. Don't forget all the other plugs too! Run the cables behind the unit and screw it back into place (4 screws) and you should now have 3 cables to run from the top screen to the android unit. I ran them along the DS of the other AV units in the gap between their backets and the console, and used some corrugated tubing on the sharp edges of the bracket so the wires were safe. Plug the centre console and lower screen in temporarily and turn the car to ACC, the AV should fire up as normal. Hold the back button for 3 sec and Android should appear on the top screen. You need to set the input to Aux for audio (more on that later). I put the unit under the AC duct in the centre console, with the wifi antenna on top of the AC duct near the shifter, the bluetooth antenna on the AC duct under the centre console The GPS unit on top of the DS to AC duct; they all seem to work OK there are are out of the way. Neat cable routing is a pain. For the drive recorder I mounted it near the rear view mirror and run the cable in the headlining, across the a pillar and then down the inside of the a pillar seal to the DS lower dash. From there it goes across and to one USB input for the unit. The second USB input is attached to the ECUtec OBD dongle and the 3rd goes to the USB bulkhead connected I added in the centre console. This is how the centre console looks "tidied" up Note I didn't install the provided speaker, didn't use the 2.5mm IPod in line or the piggyback loom for the Ipod or change any DIP switches; they seem to only be required if you need to use the Ipod input rather than the AUX input. That's it, install done, I'll follow up with a separate post on how the unit works, but in summary it retains all factory functions and inputs (so I still use my phone to the car for calls), reverse still works like factory etc.
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      Place the new daughterboard in the case and mount it using the 3 small black rivets provided, and reconnect the 3 factory ribbon cables to the new board Then, use the 3 piggyback cables from the daughterboard into the factory board on top (there are stand offs in the case to keep them apart. and remember to reconnect the antenna and rear cover fan wires. 1 screw to hold the motherboard in place. Before closing the case, make a hole in the sticker covering a hole in the case and run the cable for the android unit into the plug there. The video forgot this step, so did I, so will you probably. Then redo the 4 screws on back, 2 each top and bottom, 3 each side and put the 2 brackets back on.....all ready to go and not that tricky really.      
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      Onto the android unit. You need to remove the top screen because there is a daughterboard to put inside the case. Each side vent pops out from clips; start at the bottom and carefully remove upwards (use a trim remover tool to avoid breaking anything). Then the lower screen and controls come out, 4 screws, a couple of clips (including 3 flimsy ones at the top) and 3 plugs on the rear. Then the upper screen, 4 screws and a bunch of plugs and she is out. From there, remove the mounting brackets (2 screws each), 4 screws on the rear, 2 screws top and bottom and 3 screws holding in the small plates on each side. When you remove the back cover (tight fit), watch out for the power cable for the fan, I removed it so I could put the back aside. The mainboard is held in by 1 screw in the middle, 1 aerial at the top and 3 ribbon cables. If you've ever done any laptop stuff the ribbon cables are OK to work with, just pop up the retainer and they slide out. If you are not familiar just grab a 12 year old from an iphone factory, they will know how it works The case should now look like this:
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      Switching the console was tricky. First there were 6 screws to remove, and also the little adapter loom and its screws had to come out. Also don't forget to remove the 2 screws holding the central locking receiver. Then there are 4 clips on either side....these were very tight in this case and needed careful persuading with a long flat screw driver....some force required but not enough to break them...this was probably the fiddliest part of the whole job. In my case I needed both the wiring loom and the central locking receiver module to swap across to the new one. That was it for the console, so "assembly is the reverse of disassembly"
×
×
  • Create New...