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Thread: I have a problem with my 1990 xr7

  1. #1
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    I have a problem with my 1990 xr7

    I bought my 1990 xr7 as my first car and i am having problems with the car jumping idle. I replaced the DIS and it still has not stopped but it only occurs when the tac kicks off and then I have to stop rev it up and the bucking goes away. Has anyone else ever had this problem and how did you fix it.

  2. #2
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    Usually when you loose the tach it's related to the cam sensor. Mine had similar issues when the cam sensor went south. Usually accompanied by hard starts also.

    -Tim
    Current Collection
    1994 Thunderbird SC - Auto converted to 5spd

    1995 Thunderbird SC - Auto

    1994 Thunderbird SC - 5spd
    1989 Thunderbird SC - 5spd - Daily Driver
    1990 Thunder/Cougar XR7 - 5spd
    1994 Thunderbird SC - 3v Project

  3. #3
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    sometimes it has trouble turning over to it will take a couple tries before it will start. Is it a hard fix or is it more of a simple fix

  4. #4
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    Cam sensor is the hockey puck shaped sensor under the snout of the supercharger. If you want to test that it is in fact the culprit of your problems you can unplug the sensor. With the sensor unplugged the car will usually start within 3-5 turns of the key and run off the base tuning in the EEC.

    As for replacement, it's pretty simple 2 screws hold the sensor in place...5.5mm or 7/32 socket to remove the screws. Remove the bad, replace with the new...sensor is $25-$35 at most parts stores.

    -Tim
    Current Collection
    1994 Thunderbird SC - Auto converted to 5spd

    1995 Thunderbird SC - Auto

    1994 Thunderbird SC - 5spd
    1989 Thunderbird SC - 5spd - Daily Driver
    1990 Thunder/Cougar XR7 - 5spd
    1994 Thunderbird SC - 3v Project

  5. #5
    Join Date
    Jul 2005
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    359
    Good afternoon

    This is a basic inspection and heads up guide that can be applied to your 1990 XR7.



    https://www.google.com/url?sa=t&rct=...T3ANbkQZhI2dqQ


    Good Luck.
    Last edited by sam jones; 11-23-2016 at 07:49 PM.

  6. #6
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    Quote Originally Posted by Tim Groth View Post
    Cam sensor is the hockey puck shaped sensor under the snout of the supercharger. If you want to test that it is in fact the culprit of your problems you can unplug the sensor. With the sensor unplugged the car will usually start within 3-5 turns of the key and run off the base tuning in the EEC.

    As for replacement, it's pretty simple 2 screws hold the sensor in place...5.5mm or 7/32 socket to remove the screws. Remove the bad, replace with the new...sensor is $25-$35 at most parts stores.

    -Tim
    thanks Tim I'll try that later today

  7. #7
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    So I fixed the cam sensor and it drove nice for about a week and now the crank sensor has went bad so Tuesday that will get done. Are there any other sensors I should replace while I do the crank sensor. I have already done the dis and the cam sensor

  8. #8
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    Quote Originally Posted by Nkuk35 View Post
    So I fixed the cam sensor and it drove nice for about a week and now the crank sensor has went bad so Tuesday that will get done. Are there any other sensors I should replace while I do the crank sensor. I have already done the dis and the cam sensor
    Sounds like you took care of the main sensors at this point. If it were mine I'd replace the Harmonic Balancer while there. I found the lowest price is:

    http://www.oreillyauto.com/site/c/de...eyword=pb1530n

    Just did this on my '89 SC for piece of mind.

    -Tim
    Current Collection
    1994 Thunderbird SC - Auto converted to 5spd

    1995 Thunderbird SC - Auto

    1994 Thunderbird SC - 5spd
    1989 Thunderbird SC - 5spd - Daily Driver
    1990 Thunder/Cougar XR7 - 5spd
    1994 Thunderbird SC - 3v Project

  9. #9
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    I had the harmonic balancer replaced shortly after I bought the car my mechanic recommended it. I also did the radiator and the intercooler because they where rusted through. I hope this is the last problem i have with the car. The ball joints, rotors, and calipers have been replaced also because it sat for so long.

  10. #10
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    Quote Originally Posted by Nkuk35 View Post
    I had the harmonic balancer replaced shortly after I bought the car my mechanic recommended it. I also did the radiator and the intercooler because they where rusted through. I hope this is the last problem i have with the car. The ball joints, rotors, and calipers have been replaced also because it sat for so long.
    Sorry, but I have to LOL. Just be patient, and consult the search on this website for your the next problem. As for running problems, as long as you have the main 3 (DIS,cam sensor,crank sensor) you should be good to go. New replacement Cam sensors BTW, are hit and miss. I've had poor results with them.

  11. #11
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    So I have replaced the crank sensor, cam sensor, DIS, and even the coil and plug wires and the car still likes to buck once it gets warmed up I have no Idea what is going on so I am having the computer replaced. Is there anything else that can cause this problem that I don't know about.

  12. #12
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    Quote Originally Posted by Nkuk35 View Post
    So I fixed the cam sensor and it drove nice for about a week and now the crank sensor has went bad so Tuesday that will get done. Are there any other sensors I should replace while I do the crank sensor. I have already done the dis and the cam sensor
    Good morning


    - Do a scan and address any codes.

    - Check motor and transmission mounts. It will be flustrating replacing the oil filter. Failed engine mounts could cause the power steering rack high pressure line and or oil pan to leak.

    As for you question on "bucking" make sure you apply a quality heat sink to the bottom of the DIS.


    Good Luck.

  13. #13
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    Quote Originally Posted by sam jones View Post
    Good morning


    - Do a scan and address any codes.

    - Check motor and transmission mounts. It will be flustrating replacing the oil filter. Failed engine mounts could cause the power steering rack high pressure line and or oil pan to leak.

    As for you question on "bucking" make sure you apply a quality heat sink to the bottom of the DIS.


    Good Luck.
    The motor and tranny mounts are fine and the car has no problem steering. I've replaced the cam sensor, crank sensor, plugs, plug wires, coil, and the DIS. Now it only bucks once it warms up so now I am having the computer replaced. Is there any other electrical components that can cause this to happen that i should look in to?

  14. #14
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    Quote Originally Posted by Nkuk35 View Post
    The motor and tranny mounts are fine and the car has no problem steering. I've replaced the cam sensor, crank sensor, plugs, plug wires, coil, and the DIS. Now it only bucks once it warms up so now I am having the computer replaced. Is there any other electrical components that can cause this to happen that i should look in to?
    When you installed the plug wires on the the plugs, did they click into place? If your hands didn't hurt afterwards, you probably didn't get them seated.

  15. #15
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    Jul 2005
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    Good morning


    A bad DIS /DIS without a quality heat sink compound applied and a MAF sensor could cause your problems. Try search.


    http://www.sccoa.com/forums/showthre...-Misfire/page2


    http://www.sccoa.com/forums/showthre...r-buckin/page2


    http://www.sccoa.com/forums/showthre...r-bucking-bird


    http://www.sccoa.com/forums/showthre...ing-Rough-Buck



    Good Luck.

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