Question about 1997 Mercury Grand Marquis

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Code 171 and 174 on a 97 mercury grand marquis

Engine idles high then low and car hesitates when i hit the gas and hesitates really bad when first strat up in morning put code scanner on it and got code 171 and 174 banks lean changed throttle position sensor per advice from friend same guy suggested maf sensor any help

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I've owned one of these. you can try to clean the MAF with brake cleaner. but if that doesn't work you'll have to replace it. the car can't tell how muich air is entering the engine to properly meter the fuel. so what you get is a lean misfire. fix it soon. running the engine lean means it's running hot internal temperatures which can damage expensive things ie. catylitic converters.

Posted on Jun 24, 2009


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Posted on Jan 02, 2017


SOURCE: i am having a problem with a 2001 ford windstar.

Two bad O2 sensors is rare. The problem is before the sensor,intake vacuum leak, injector lower o-ring, IMCR stuck open or the control rod is off, vacuum hose(s) off, or MAF sensor. If this has a plastic upper intake, they had problems with o-rings.

Posted on Oct 07, 2009

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SOURCE: check engine light on computer codes 171 174

switch, we run off snitches. 171 174 banks 1 & 2 Lean. Most likely cause are Upper Intake Manifold Gaskets, failed seals. It's not 1990 on. It's 1996 and on OBD2.

Posted on Nov 03, 2009

  • 462 Answers

SOURCE: shake rattle then roll. rough idle last few weeks

The intake manifold gaskets are the most likely cause of your problem. Have the fuel pressure tested also.

Posted on Jan 04, 2010

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SOURCE: i have 2 codes on my 2000 silverado they are 171

Lots of things can cause an engine to run lean. The most common problem with the 3rd gen small block is the upper plenume (the intake manifold) gaskets **** air. This is an easy job, some of the bolts look hard to get to but they really are not.
Make sure you have good fuel pressure and there are not any other codes in the system.
The best way to see if the intake gaskets are sucking air would be to spray a small amout of carb spray around the intake while the engine is running and see if it starts running real bad, like a missfire. BUT becarful with this as carb spray is flamable and an engine can be hot, so you would want to try this after the engine has cooled down.

Posted on Oct 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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