Question about 1998 Mercury Mystique

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Choke not working? low idle barely runs then crescendo's up

Barely runs then it catches and rev-es up around 3000 rpm, and then back to barely running, keeps repeating this pattern. Getting trouble codes 171,174,430,1131,1151 Have replaced O2 sensors in last year, plus trouble codes are suggesting lean burn on both banks. I believe its my idle control valve, but would like a little back up before I spend 100.00 Anyone have an opinion

PS: The temp here has been between 0 and -10

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  • thursty21 Jan 28, 2009

    Runs the same hot or cold, starts right up no problem. Have not checked temp sensor

  • thursty21 Jan 28, 2009

    Thanks, both you and a mechanic friend have confirmed my suspicions of the IAC. Did the guy in Alberta say if the car would start at all?

  • Richard Scordino May 11, 2010

    If same hot or cold , more likely IAC. If it cleared up hot, temp sensor would be more in play.. I talked to a guy in Alberta Canada a few weeks ago who found ice in the IAC ??? cold temps cause wierd stuff. But once hot this would also disappear!

  • Richard Scordino May 11, 2010

    You don't have a choke. Did you check the temp sensor? Idle control sounds reasonable. How does it run when warmed up?



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The problem is solved, the IAC (idle Air control valve) was the problem. I was glad to be able to bounce this off someone, and get a fast accurate response! Many thanks to Thunder God!!


Posted on Jan 31, 2009


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Posted on Jan 02, 2017

  • 77202 Answers

SOURCE: system to lean codes 1131

You need to replace the O2 sensors according to the codes definition in the repair manual

Posted on Oct 02, 2008

  • 199 Answers

SOURCE: codes #171 & 174

first check out for o2 sensor if its faulty this can show up.but if its proper.Evaporative emission control system leak very small 171 System too lean (bank 1) 174 System too lean (bank 2) 

Posted on Jan 05, 2009

  • 2 Answers

SOURCE: I have a volvo s80 t6 with error codes 171 and 174

2 things to check air leaks from air box tomanifold where it meets at engine check mass air flow sensor and oxygen sensor start with common sense things first

Posted on Apr 16, 2009

  • 169 Answers

SOURCE: I have a check engine light on my 1999 Chev

9 out of 10 times this is due to a dirty MAF sensor. If you run an aftermarket air intake that uses an "oiled" filter - you greatly increase your chances of this. You can purchase "electronics parts cleaner" from an auto parts store and spray it on the MAF sensor (you'll have to remove any intake tubing to get to it) and clean it. BE VERY CAREFUL to not damage the sensor - don't attempt to wipe it off on the inside, you can damage it beyond repair.

Hope this helps and good luck!


Posted on Sep 18, 2009

  • 68 Answers

SOURCE: 97 Mercury cougar xr7 v6. po443, po430, po171, po174,

Sounds like you have low fuel supply or a leak in intake system causing lean codes, check fuek pressure and volume first. Cat converter effeciancy could be caused by the lean codes, purge system sounds like solenoid failure, check for high resistance accross purge vent solenoid.

Posted on Mar 08, 2010

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