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Misfire Coil or Plug...

Discussion in 'Range Rover' started by Doo, Feb 12, 2020.

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  1. Datatek

    Datatek Well-Known Member

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    Yes it could still be a wiring or connector issue.
     
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  2. Grrrrrr

    Grrrrrr Technician, Bodgit & Scarper Ltd

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    +1.

    Maybe it is meant to read that? Although it would explain it running rich but why only #3?
     
  3. tomcat59alan

    tomcat59alan Well-Known Member

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    I like a man who bears a grudge.;):D:D
     
    Doo likes this.
  4. Doo

    Doo Well-Known Member

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    So, did the deed. Cats were trashed on the left bank and fairly gubbed on the right :confused:

    Silly me had left the old one unplugged, so when I did the code reading, it read the default thing as Datatek said. Plugged in both old then new MAF and identical readings :(

    So looking like the plug is still a possibility or the wiring is not happy. Bloody car :rolleyes:

    Still, the new exhaust system is shiny :D

    Photo's self explanatory ...

    [​IMG]

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    [​IMG]

    [​IMG]

    [​IMG]

    Then a short break....:cool:

    [​IMG]

    Used an old shelf that had been consigned to the bin, made it into guards for the cats since the old ones had folded long ago.... They may also help hide any "ahem" work :oops:

    [​IMG]

    [​IMG]

    And the new shiny middle and ends :cool:

    [​IMG]



    So, at least she sounds slightly better... Just wish I could trace this bloomin MAF fault o_O
     
    Grrrrrr likes this.
  5. Doo

    Doo Well-Known Member

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    Well, Faulty coil! Engine would run fine, then under load, bag of bolts in a tumble dryer. New coil sorted that.

    The MAF.

    EUREKA!

    I think.....o_O

    Nice chap supplied a wiring diagram for the Bosch THOR V8.

    Pin numbers at the MAF sensor plug:

    1 = Air Temp Sensor
    2 = 12v
    3 = Ground
    4 = 5v
    5 = MAF signal

    However, having tested mine again, I found:

    1 = 5v
    2 = 12v
    3 = Ground
    4 =
    5 =

    Now the last two pins show nothing until I put the + probe on 12v and the ground probe on number 4 upon which it shows -12v with engine off, ign on.

    I have to assume the asshats in Stirling who made a royal cock up of the LPG have wired it wrong AND removed the EML (since day one I was aware there was no EML on my dash, but concluded it was too old to have one :rolleyes: It was only after seeing someone else's car with one that the penny dropped).

    So, do I swap the wires to the correct pins and hope for the best? And hopefully, if I replace the missing EML bulb, will it go out or stay lit :confused:

    I know what Doo must do, but I'm looking for permission :D
     
  6. DanClarke

    DanClarke Well-Known Member

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    Oh go on.... you know you want to. It can't get much worse. At least you can put it back to this faulty state and be no worse off.
     
    Doo likes this.
  7. Doo

    Doo Well-Known Member

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    Having trawled for ages I found this pic reference and it's looking like I simply need to swap pin 1 & pin 4. Pin 4 is giving me a ground with ign on, so that suggests it's driven from the ECM. And if I give pin 4 it's 5v reference, then pin 5 should come to life :cool:

    [​IMG]
     
  8. Datatek

    Datatek Well-Known Member

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    Maybe you should find out why pin 4 does not have 5 volts with the ignition on before you start swapping wires about? What voltage do you have on pin 1? Pin 1 is in effect an output from the MAF.
     
  9. Doo

    Doo Well-Known Member

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    Pin 1 has 5v and pin 4 only has a ground feed with the ign on.

    I think the LPG muppets mixed up the colours...
     
  10. Datatek

    Datatek Well-Known Member

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  11. Datatek

    Datatek Well-Known Member

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    Pin 1 may well appear to have 5 volts on it, it goes to the thermistor which gives the ECU air temperature, the other end of the thermistor is connected to ground, so connecting the ground from pin 4 will render it inoperative.
     
  12. Doo

    Doo Well-Known Member

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    Pin 1 most definitely "has" 5v and pin 5 has 0 feed either way.

    My thoughts were that pin 4 needs 5v for pin 5 to complete the circuit for the Wheatstone bridge. So because it has no 5v feed, it's kinda like a tail light circuit where it creates a floating earth....

    If I leave out pin 4 (not connected to anything) and connect 5v to pin 4 then test for an output from pin 5.

    Once I've done that, I can test for any voltages (+ or - ) at pin 1. If it is fine, I can try to connect it. Whats the worst that can happen? Won't make it any worse after all :rolleyes:
     
  13. Datatek

    Datatek Well-Known Member

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    Pin 4 certainly needs a 5 volt reference for the MAF to operate, this should be a very accurate voltage supplied by the ECU. The voltage on pin 1 is likely to be a floating voltage from the input circuit in the EDC that will vary up and down as the thermistor resistance changes.
    It's not likely to do any harm to swap the wires, personally I would be looking at the ECU to find out if the wires go to the right pins and then at the ECU itself.
     
  14. Doo

    Doo Well-Known Member

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    Replaced the ECU, no change. Checked voltages, no change. I did a live data and at 60mph in 0 degree's Celcius ambient air temp last night, it was showing varying degree's of temperature during a 3 minute recording of between 9C and 11C. That was clearly wrong. It did, however, appear to be reading a flow of air (although I stand to be corrected) but I suspect this too was incorrect...
     
  15. Doo

    Doo Well-Known Member

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    Replaced the coil which appeared to fix #3 misfire... Then it came back :rolleyes: It was a shitpart, so it could be that, but I doubt it.

    I did the MAF, but made no difference as the fault is still there. And including the misfire I have 4 codes MAF, misfire #3, multiple cylinder misfires and danger to the cat (even though there are none).

    This all started when I changed to Magnecor leads :eek: and I am wondering if there is the slightest chance #3 lead "could" be iffy o_O

    However, even though there is a misfire detected (and felt) the sparks look to be fine and fat and regular! (I use those spark tester things you put on the spark plug and the lead on the other end and all of both banks are flashing perfectly).

    There doesn't appear to be any issues with the sparks according to the code reader as I also tested all 8 which showed varying degrees of angle on any given throttle position. No misfire detected so HAS to be injector or wiring. But the live data doesn't show any injector faults o_Oo_Oo_O

    I'm planning to buy a new crank sensor just for shits & giggles because it is not unheard of that it could be slightly iffy. In the last four years the engine has just died for no apparent reason on a few occasions as pulling up to lights or pulling away. But trawling the net I found on an American site that someone had that exact issue of misfire reported, but it was in fact the CS. I'll try anything at this point.

    I spoke to the local engineer who is amazing with codes and faults and although he will not touch LPG, he said he thought the system may have had the air temp bypassed on the MAF because the LPG system had it's own air temp sensor built in. However, I can't understand how it could work on petrol unless they figured it didn't matter as it would only run open loop until the coolant heated up enough to switch to LPG... Who knows what devious plans these gas boys cooked up :rolleyes:

    Anyone on here have a spare engine loom for a 2000 Bosch THOR without LPG?
     
  16. Grrrrrr

    Grrrrrr Technician, Bodgit & Scarper Ltd

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    Hard to see how crank sensor could affect only 1 cylinder. When mine started to fail it was when engine was hot and it just died.
     
  17. Datatek

    Datatek Well-Known Member

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    Variation in the gap to the pick up triggers on the flywheel could affect a dodgy CS
     
  18. RangeRoller dt

    RangeRoller dt Well-Sprung Member

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    One pin missing....where are the flywheel pins on an auto?
     
  19. Doo

    Doo Well-Known Member

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    New Crank Sensor cured my misfires :cool:

    I videoed the spark testers and it shows the timings are "strange" o_O They flash several times on 3/5 then move to 1/7 then back and forth when in fact, they should "look" as if they are all firing at once :eek:

    What a difference :)

    All this time and it was a £45 part :rolleyes:

    I'm buying another just to keep as a spare ;)

    The reason I didn't initially think of the Crank Sensor is because they usually die when hot as opposed to cause a misfire :confused:

    Stoopid car :oops:
     
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  20. Grrrrrr

    Grrrrrr Technician, Bodgit & Scarper Ltd

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    Good spot there, Doo.

    I'm with you on that. Usually start to fail hot and either work or not. Strange that it caused a MAF fault.
     
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