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Thread: RPM tach and check engine light

  1. #1
    Join Date
    Sep 2003
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    33

    Thumbs down RPM tach and check engine light

    `I have a 93SC , sometimes the rpm needle goes limp and the check engine light then comes on, when that happens the car will sometimes stall and then I have a hard time starting it again. Eventually the rpm needle will go back to regular idling position and the check engine light goes out.

    I had a diagnostic test done and the only code that came up was for the MAF
    which was cleaned, could it be the crank sensor? Appreciate any help on this
    annoying problem, the other day I was on the QEW and luckily coasted onto the shoulder after a few minutes the car turned over and the rpm tach was normal and no check engine light.

  2. #2
    Join Date
    May 2003
    Location
    London Ontario
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    I had the same problem with mine a few years back. The only other symptom I had at the same time was the car would shake. Ended up being the ignition module. Hope that helps.
    SCCoA Member # 2246


  3. #3
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    Apr 2002
    Location
    Caledon, Ontario ... CANADA !!!
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    Those are often symptoms of a bad crank sensor, on the 89 - 93 cars too.

    cheers
    Ed N.

  4. #4
    Join Date
    Sep 2003
    Posts
    33
    Quote Originally Posted by fast Ed N
    Those are often symptoms of a bad crank sensor, on the 89 - 93 cars too.

    cheers
    Ed N.
    yeah I think IM gonna replace the crank sensor , thanks for the info.

  5. #5
    Join Date
    May 2003
    Location
    Toms River NJ
    Posts
    279

    same problem...

    mine also did that for about a week and then the crank snapped...

  6. #6
    Join Date
    Feb 2005
    Location
    Toronto, ON
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    4,181
    Quote Originally Posted by nick2003
    `I have a 93SC , sometimes the rpm needle goes limp and the check engine light then comes on, when that happens the car will sometimes stall and then I have a hard time starting it again. Eventually the rpm needle will go back to regular idling position and the check engine light goes out.

    I had a diagnostic test done and the only code that came up was for the MAF
    which was cleaned, could it be the crank sensor? Appreciate any help on this
    annoying problem, the other day I was on the QEW and luckily coasted onto the shoulder after a few minutes the car turned over and the rpm tach was normal and no check engine light.
    Have the same problem. took it to Ford, they suggested to change a crank sensor. I changed it, but no luck. Also, changed a TPS sensor, same results. Was adviced to change a DIS module. Looks like it didn't help either...
    Dzmitry Batsiai - President of the Super Coupe club of Ontario
    Black 90 ARed SC: 11.832@119.88 at 2009 Shootout

  7. #7
    Join Date
    Sep 2004
    Location
    Peterborough, Ontario, Canada
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    272
    Is our ring that is read by the crank sensor on the end of the crank or on the balancer? If its on the balancer your balancer could be breaking and causing the non read signal to the crank sensor.

    Just a though

    Garett

  8. #8
    Join Date
    Apr 2002
    Location
    Hamilton, Ontario, Canada
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    5,420
    Quote Originally Posted by crabmustang302
    Is our ring that is read by the crank sensor on the end of the crank or on the balancer? If its on the balancer your balancer could be breaking and causing the non read signal to the crank sensor.

    Just a though

    Garett
    Garett,

    On the early style balancers ('89 to '93 inclusive), the sensor ring is mounted to the inner hub on the balancer. When the balancer fails, it's usually the outter ring that comes loose. If the balancer was about to fail, I suppose it's possible that the sensor ring might be moving around other than in the circle that it's supposed to follow, because things are 'out of balance', but the ring isn't mounted to the part of the balancer that typically comes loose (due to failure of the polymer that binds the outter ring to the inner hub)

    It may be the same case on the '94-'95 style balancers, but I've never seen one up close to know.

    ...I'm not disputing your suggestion though. IMO, it is possible that nick2003's balancer is nearing failure, and occassionally the sensor ring moves away from the sensor enough that it fails to get a good reading.

    Payton, did you remember to put some fresh heat-sink compound under the replacement DIS Module? That stuff is important.

    Best regards,

    Sean

  9. #9
    Join Date
    Dec 2004
    Location
    Woodslee - Ontario, Canada
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    702
    I had the same problem a few days before I spun a rod. And it did it the same morning I was driving to school and about 10 minutes later it did it again, but then the squeaking and knocks started and that was all my engine did until it finally died later that afternoon.

  10. #10
    Join Date
    Sep 2004
    Location
    Peterborough, Ontario, Canada
    Posts
    272
    Thanks for the info Sean, I`m new to the SC`s, I have built several Turbo fords and put in stangs and such, It was just a thought when I was reading the thread and thought might help.

    If all goes well I`m going to put a SC motor and trans into my 83 stang I have.

    Sorry to get off topic, but if someone has a motor and trans and wiring harness and computer and any other parts needed, please pm me with what you have and a price.

    Thanks
    Garett

  11. #11
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    Feb 2005
    Location
    Toronto, ON
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    Quote Originally Posted by SeanMatteson

    Payton, did you remember to put some fresh heat-sink compound under the replacement DIS Module? That stuff is important.

    Best regards,

    Sean
    Yes, Sean, I did put a lot of dielectric grease in between The thing is I bought a used DIS, there is no warranty it's working properly. After I changed it, I was driving my car for a week without a problem, and then, all of a sudden, it started to give a hard time again
    Dzmitry Batsiai - President of the Super Coupe club of Ontario
    Black 90 ARed SC: 11.832@119.88 at 2009 Shootout

  12. #12
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    Apr 2002
    Location
    Hamilton, Ontario, Canada
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    5,420
    Quote Originally Posted by Payton
    Yes, Sean, I did put a lot of dielectric grease in between The thing is I bought a used DIS, there is no warranty it's working properly. After I changed it, I was driving my car for a week without a problem, and then, all of a sudden, it started to give a hard time again
    Payton,

    Dielectric grease is not the same thing as heat-sink compound. You can buy heat-sink compound from Radioshack. I would try to replace the dielectric grease with heat-sink compound first, and see if maybe you've just overheated your DIS a little.

    Regards,

    Sean

  13. #13
    Join Date
    Jun 2004
    Posts
    262
    Hi Nick

    This sounds like exact symptoms I had last year. Check engine light on rpm 0 check engine light off rpm normal. It was my cam position sensor that went. Cheapest sensor of the bunch and easiest to change. Give it a try

    Good Luck
    Craig

  14. #14
    Join Date
    Feb 2005
    Location
    Toronto, ON
    Posts
    4,181

    Question

    Quote Originally Posted by SeanMatteson
    Payton,

    Dielectric grease is not the same thing as heat-sink compound. You can buy heat-sink compound from Radioshack. I would try to replace the dielectric grease with heat-sink compound first, and see if maybe you've just overheated your DIS a little.

    Regards,

    Sean
    Oh, man, this heatsink compound is hard to find. I believe I was in about a dozen computer stores all over Downtown Toronto and it seens all of them were out of stock...
    I was thinking about another thing: what if I put a layer of something with low heat conductivity rate in between??? Let say a plate of metal under the DIS module?
    Last edited by Payton; 03-07-2005 at 08:06 PM.
    Dzmitry Batsiai - President of the Super Coupe club of Ontario
    Black 90 ARed SC: 11.832@119.88 at 2009 Shootout

  15. #15
    Join Date
    Nov 2004
    Location
    Brantford, ON
    Posts
    5,372
    Quote Originally Posted by Payton
    Oh, man, this heatsink compound is hard to find. I believe I was in about a dozen computer stores all over Downtown Toronto and it seens all of them were out of stock...
    I was thinking about another thing: what if I put a layer of something with low heat conductivity rate in between??? Let say a plate of metal under the DIS module?
    The idea is to suck all the heat out of the DIS module into the a/c bracket that you can, not hold heat in it. A low heat conductive metal will only make the problem alot worse. You need to get that heatsink compound on there, as it conducts heat faster than the surrounding metals, and the a/c bracket metal will absorb heat faster than the DIS module.......... hopefully that is .

    Unfortunately everything gets heat soaked after awhile and that shortens the life expectancy of the DIS module.... in other words, accountants got involved again in the design process and screwed it up as usual .

    I've been reading that folks have used artic silver heat sink compound that is used with heat sinks in computers successfully with the DIS module, so you might want to check that out.

    Frit

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