BX 16 valve - where's the TDC sensor? Firing on 2 cylinders
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  1. #1
    Fellow Frogger! blahblah's Avatar
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    Default BX 16 valve - where's the TDC sensor? Firing on 2 cylinders

    Hello

    I've put my 16 valve back together after a head recon and it appears to be firing on 2 cylinders... I checked and double checked the timing belt etc before starting it, I have compression, oil pressure and I put in new plugs, leads, distributor cap and rotor arm. It doesn't run with all the old leads etc either. As there's fuel and spark, I'm wondering if the TDC sensor wiring has been diisturbed or it has failed. The BX haynes manual is no help other than to say the sensors on the bellhousing...

    I'm buggered if I can see it! So does anyone have any accurate directions on where it is or any suggestions on what else this might be?

    Cheers,

    Chris

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  2. #2
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    order of the leads? may want to double check
    1984 505 STI

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    Quote Originally Posted by lunchcutter
    order of the leads? may want to double check
    Yes, checked that, thanks. It's odd - I'm thinking the TDC sensor as that is what (presumably) defines when the engine fires. I had the injectors serviced while it was in bits and took great care not to turn the crank so that it went back together the same way.

    Cheers,
    Chris

  4. #4
    1000+ Posts PeterT's Avatar
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    If you used the timing locating holes, one in each cam pulley and one in the crank, it's almost impossible to get the cam timing wrong. The TDC sensor can only be in one position, and given that you've got fuel and spark, that can't be wrong.

    It's more likely a high tension issue. It's possible for the rotor button to fail, causing spark to fire out the back, 180 deg. out. I'd be checking the distributor first, making sure that each lead is working. Check each lead with a timing light.

    There are no external timing marks on a 16V because there is no adjustment.

    '92 205 Mi16
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  5. #5
    Moderator Alan S's Avatar
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    Plug leads 2 & 3 are identical. You did swap these two to try them?
    Failing that, if you're using Bougichord leads, you haven't got the problem of the big square outer blocks grabbing on the head and making you believe that you have the actual leads connected to the plugs?
    I spray the outers of mine with silicone spray and paint silicone grease around the section that sits onto the porcelain of the plugs. Tht happens more times than peple wish to admit to.
    Next option is to be 100% sure that the plugs on the injectors have connected to the pins on the injectors and not slid back up inside the actual plug. That's a common problem when they've been disconnected. (mumbles; "How many times have I been caught with that one" as he kicks the dog)


    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

  6. #6
    Fellow Frogger! blahblah's Avatar
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    Quote Originally Posted by Alan S
    Plug leads 2 & 3 are identical. You did swap these two to try them?
    Failing that, if you're using Bougichord leads, you haven't got the problem of the big square outer blocks grabbing on the head and making you believe that you have the actual leads connected to the plugs?
    I spray the outers of mine with silicone spray and paint silicone grease around the section that sits onto the porcelain of the plugs. Tht happens more times than peple wish to admit to.
    Next option is to be 100% sure that the plugs on the injectors have connected to the pins on the injectors and not slid back up inside the actual plug. That's a common problem when they've been disconnected. (mumbles; "How many times have I been caught with that one" as he kicks the dog)


    Alan S
    Alan,
    You're right about the plug leads - they do stick in the head. I've got a tub of silicone grease so I'll use a smear of that on the leads.

    I've spoken to the guys who serviced the injectors for me and I described the problem. They specialise in Bosch injection and have always done the right thing by me so I trust them. I mentioned that I hadn't fitted the injectors and started the car within a day or so of getting the injectors back - apparently the cleaning fluid left in the injectors causes the sticking when it dries and when they tested them two worked and two were pretty feeble!! Apparently CRC is the go for stopping the injectors sticking. The injectors were stored for 2-3months.....

    When I tested that there was fuel I just took out each plug and smelt it - I could smell raw fuel. Makes mental note to pull the fuel rail off next time and do it properly! I'll fit the injectors this weekend after they've been cleaned and hopefully it will fix it. I'll confirm with another post because this is worth keeping in mind if someone is thinking of servicing their injectors while the car is off the road for a while.

    In hindsight, I would have thought the Motronic warning light would have come on with failure of the TDC sensor...


    Thanks for the help.

    Cheers,

    Chris

  7. #7
    Fellow Frogger! blahblah's Avatar
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    Well it was definitely the injectors causing it to run on two cylinders. I didn't realise that the cleaning fluid could cause the injectors to stick. It now runs on all four cylinders although it does sound a bit tappety.

    Do the hydraulic lifters take a while to pump up ????



    Cheers,

    Chris

  8. #8
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    my engine sounds quite tappety aswell. Recently I didn't drive it for about 3 weeks and when I started her up the clicking sound was VERY loud. It died down to 'normal' levels fairly soon after running the engine for a bit though. apparently these engines don't really get as much oil to the lifters as would be desirable but I don't think its generally an issue.
    1984 505 STI

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