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Thread: 90 SC won't idle :(

  1. #1
    Join Date
    Sep 2010
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    east san francisco bay
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    90 SC won't idle :(

    Hi, I'm in Northern California and inherited a beautiful, low mileage, well maintained SC which initially ran great. Then it idled too rough when it came time to pass smog...smog guy said it was my plug wires...tried changing them myself and had to park it, so the registration lapsed. Finally, had a mobile mechanic friend come change the wires. It still won't idle--runs rough and tries to die. Mobile mechanic had a scope and checked everything he could, fuel filter, oxygen sensor and whatever he could. He wasn't getting error codes and check engine light is not on. He said he didn't have the right scope. Finally told me to put in fuel injector cleaner and just run it. It still won't idle!! I don't have a lot of money so don't want to take it to the dealer. It has now been four years in the driveway. All I can do is clean it and/or sit there holding the idle up so it will run.

    My neighborhood mechanic said he doesn't think he can fix it. They are good guys to be honest so I said I'd go somewhere else. Does anyone have any suggestions for me (besides giving up)? What can I ask shops in order to know if they are capable of fixing it? I don't really understand why mechanics might be unwilling to try to get this car running, but maybe you do. Thanks for any advice! I really hope for some help.

  2. #2
    Join Date
    May 2012
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    Denver Area
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    Ann - have you tried pulling codes out of the EEC? Where in Northern Cali? I'm heading to Ukiah tomorrow for work for the week and could take a peek (or at least try to pull codes with you). The last time my SC wouldn't idle correctly it was the crank position sensor. I'm not advocating you go out and buy one. Replacing parts in shotgun mode isn't a cost effective way to do things.

  3. #3
    Join Date
    Jun 2008
    Location
    Columbia,SC
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    try pulling the iac connector...connected to throttle body on right...sometimes when it is having trouble finding idle this little guy is screwed up and not allowing enough air in...if you unplug and it doesnt die completely it may be faulty.

  4. #4
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    or perhaps its just a vacuum leak from a loose connection or broken tube somewhere...

  5. #5
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    kansas
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    Quote Originally Posted by SCarSC View Post
    try pulling the iac connector...connected to throttle body on right...sometimes when it is having trouble finding idle this little guy is screwed up and not allowing enough air in...if you unplug and it doesnt die completely it may be faulty.
    +1 usually the IAC is the most common and easiest fix for idle issues. It can Also cause a high idle that will make the car seem hard to stop. It is only held onto the throttle body by 2 8mm bolts I believe, one of which is under the IAC itself which makes it difficult to reach.
    1990 Thunderbird SC 35th Anniversary: built 3.8, stock gen 2 blower with 10% od, built aod with silver fox valve body

  6. #6
    Join Date
    Nov 2010
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    Bay Area
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    I live in Burlingame CA and not sure where you are at but more than willing to help you out. Are you sure the mechanic put the wires in the right firing order? Some of the books are wrong check this thread http://www.sccoa.com/forums/showthre...9-firing-order and get back to me. You can also shoot me a message and I will give you my cell.

    Good luck and I'm sure it's something simple!

  7. #7
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    Sep 2010
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    Quote Originally Posted by potshotscott View Post
    Ann - have you tried pulling codes out of the EEC? Where in Northern Cali? I'm heading to Ukiah tomorrow for work for the week and could take a peek (or at least try to pull codes with you). The last time my SC wouldn't idle correctly it was the crank position sensor. I'm not advocating you go out and buy one. Replacing parts in shotgun mode isn't a cost effective way to do things.
    Thanks for the offer and the idea! I'm in the bay area, so not quite as far north as you. The mobile mechanic had one computer diagnostic device, but he said it wasn't the right one. He got no error codes. so maybe he didn't check the EEC. I asked my local mechanic if he had the right scope, and he said he didn't think so. I'd like to check whatever I can check.

    Quote Originally Posted by SCarSC View Post
    try pulling the iac connector...connected to throttle body on right...sometimes when it is having trouble finding idle this little guy is screwed up and not allowing enough air in...if you unplug and it doesnt die completely it may be faulty. or perhaps its just a vacuum leak from a loose connection or broken tube somewhere...
    OK, thanks! I'll try locating the iac and try that. I sort of assumed the mobile mechanic checked for a vacuum leak, but I don't know exactly all the stuff he was trying over a period of hours. The vacuum gauge on the dash appears to be behaving normally.

    Quote Originally Posted by 35thpartdeux View Post
    +1 usually the IAC is the most common and easiest fix for idle issues. It can Also cause a high idle that will make the car seem hard to stop. It is only held onto the throttle body by 2 8mm bolts I believe, one of which is under the IAC itself which makes it difficult to reach.
    Thanks for the info! Sounds like I need to find that iac thing!
    Last edited by ann; 04-07-2015 at 12:51 AM.

  8. #8
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    Quote Originally Posted by SCDan35thANV View Post
    I live in Burlingame CA and not sure where you are at but more than willing to help you out. Are you sure the mechanic put the wires in the right firing order? Some of the books are wrong check this thread http://www.sccoa.com/forums/showthre...9-firing-order and get back to me. You can also shoot me a message and I will give you my cell.

    Good luck and I'm sure it's something simple!
    Thanks for the reassurance--yes, I'm sure it'll be the last thing I check! I'm not sure if I believe it's simple, but I sure wish it was. I helped do the wires and I am 99% sure they are correct. However, it's definitely worth double checking if you think that might be it. I don't think the engine sounds like it's missing, but maybe it runs so great that it doesn't sound like my old dodge when it's missing! I feel like the idle is just as rough as it was before the new wires.

    Tomorrow I'll be at the house where the car is and will make a recording of the engine and post that.
    Maybe something will sound familiar to someone!

  9. #9
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    Sep 2010
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    Hey SCDan35thANV, maybe you could PM me because I don't seem to be able to send you a PM. Thanks!!

  10. #10
    Join Date
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    kansas
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    One more post and you can send pm's
    1990 Thunderbird SC 35th Anniversary: built 3.8, stock gen 2 blower with 10% od, built aod with silver fox valve body

  11. #11
    Join Date
    Apr 2015
    Location
    Maricopa, AZ
    Posts
    4
    I had similar issues with my 91 when I first got it. Went through several "fixes"... I replaced the Throttle Position Sensor, the Camshaft position sensor, and I believe its called the Crank Position sensor. Seemed to help however, I then removed the ignition control module, put thermal compound and remounted it. Now all works great. I don't know which actually corrected the problem because I did two at a time but I think the thermal compound helped the most.

    Either way, I did all the above and now runs like when it was new. I have since replaced the spark plugs...amazed the car even started since they were deteriorated to almost nothing.

    If you are going to chase "gremlins", I'd recommend replacing the basics I listed above. Not too expensive.

  12. #12
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    Nov 2010
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    Quote Originally Posted by ann View Post
    Hey SCDan35thANV, maybe you could PM me because I don't seem to be able to send you a PM. Thanks!!
    As 35thpartdeux stated one more post and you can send PM's since I can't send you a pm shoot me an email at [email protected] and I'll give you my cell. If it is not the wires it could be a vacuum leak. What is your vacuum at idle? does that car start up every time? Also make sure your MAF is plugged in which is the sensor by the airbox. I have all the service manuals etc and some spare parts as well. Good luck!

  13. #13
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    Sep 2010
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    east san francisco bay
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    Unhappy still doesn't idle well enough to drive

    This poor beautiful car. I have continued to put money and time into it, but haven't found the right mechanic. It's been sitting so long in my driveway at this point that I'd be happy to find it a new home. It's getting grubby. There was only one owner before me because I inherited it, and my uncle loved this car. 65k miles. white w/ blue leather interior. It runs and drives and stops, but can't idle well enough to get smogged or be a normal car. If someone wants to inherit my SC, check the sales forum in a couple days. I will take some pics and post it in the correct forum.

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