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1997 Mercury grand marquis random stalling and rough idle
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lkmaryfla
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Jan 18, 2020, 4:40 PM
Post #1 of 12
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1997 Mercury grand marquis random stalling and rough idle
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Ive owned the car for 14 months and the whole time it will stall when slowing down and turning. It was only once a month or so but lately it is getting to be stalling weekly, and a few times a week it will idle rough and almost stall. It always happen as Im turning and slowing or coming to a stop. It was owned by someone with a system in the trunk. I almost feel it has something to do with charge system. If i turn on the ac/heat the voltage meter drops and it will kinda run rough at idle, if im driving and turn on either i cant tell and the gauge stays up. Also if i use 2 windows gauge drops. I had advance auto test it with the car on at idle and revved to 2500, both the battery and alternator came back good. Any ideas?
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lkmaryfla
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Jan 18, 2020, 4:45 PM
Post #2 of 12
(2477 views)
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Re: 1997 Mercury grand marquis random stalling and rough idle
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I hooked up a cheap obd2 scanner and took the freeze frame numbers down...Load%23.5...ShortFT1 -0.8...ShortFT2 0.8...ShortFT3 -100...ShortFT4 -100...LongFT2 0.0...LongFT3 -100...LOngFT4 -100
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 18, 2020, 5:07 PM
Post #3 of 12
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Re: 1997 Mercury grand marquis random stalling and rough idle
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Try checking plug wires before going way too nuts. I'll attempt a pic that may not show but note the length down to the plug those go and use leaks out unseen cancels that cylinder intermittently or to another.
Total hair puller to witness it do that but most leave the "carbon trace trail" on the insulation.
Your call if you find that buy just one or a set I vote for the one only on a 23ish year old unless a show car,
T
Pic? > 
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Hammer Time
Ultimate Carjunky
/ Moderator
Jan 19, 2020, 5:01 AM
Post #4 of 12
(2450 views)
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Re: 1997 Mercury grand marquis random stalling and rough idle
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First eliminate all vacuum or air leaks in the system (very important)
. You may have a bad IAC ( idle air control) but try cleaning the throttle body first. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, replace the IAC.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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lkmaryfla
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Jan 19, 2020, 12:56 PM
Post #5 of 12
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Re: 1997 Mercury grand marquis random stalling and rough idle
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I had the wires and plugs changed at a dealer. I also had the tps, iac, cts and egr changed. I also had the throttle body removed and cleaned. Thanks for the help appreciate it
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Tom Greenleaf
Ultimate Carjunky
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Jan 19, 2020, 1:15 PM
Post #6 of 12
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Re: 1997 Mercury grand marquis random stalling and rough idle
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Huh? A dealer or any professional has been at this problem and handed it back to you without some explanation? What can a web site do if pros already had it and didn't fix it IMO take it back,
T
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lkmaryfla
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Jan 20, 2020, 6:23 PM
Post #7 of 12
(2404 views)
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Re: 1997 Mercury grand marquis random stalling and rough idle
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the plugs, wires and throttle body were done at a Lincoln dealer. I changed out the sensors. right now i cant afford to take it back, that is why im here.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 21, 2020, 1:46 AM
Post #8 of 12
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Re: 1997 Mercury grand marquis random stalling and rough idle
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OK, can't afford dealer and or more too much so what do we do? 1st, you shouldn't be going to a dealer with a '97 vehicle anymore both costly and the dealers more likely to deal with the first so many years of vehicles not this old.
Ask for old parts back there's quite the collection now of things that DIDN'T work so those are probably good parts - bummer. Beware of parts tossing as the new parts are more likely to be the problem now or later if they didn't work.
Back: What you can do with little to few bucks? You can check for vacuum leaks already suggested AYOR with carb cleaner (know how and where to spray) at idle, rough if you hit a leak would smooth out or be worse on spots can focus on that spot.
I said wires once a huge problem with these some just the way they route them criss/crossed like that is/was usually ONE not all of them. THE problem was handling them more than anything else!
Random misfiring is usually vacuum related or stray spark so the carb spray and now a spray bottle of water (I use window cleaner) can find high voltage leaks AYOR again on cool parts not toasty hot or will cause a problem where there was none. See stray spark sometimes if dark or an area that gets better or worse or causes an instant stall the clue where to look.
Duh, you need to find this or will add a converter to the fix can't be happy with a random misfire but probably NOT the problem now or yet.
I'm still confused how a so called pro (can't tell what a dealer did for a tech isn't brand named to a dealership's vehicle type) so independents are a better bet. Either way handing you the car back with a bill and the same problem I don't understand if that's what you specified to be fixed?
T
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lkmaryfla
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Jan 21, 2020, 7:31 PM
Post #9 of 12
(2367 views)
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Re: 1997 Mercury grand marquis random stalling and rough idle
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My brother works at dealer so i get labor. I had them install wires and plugs and change oil, just doing a tuneup. the car had 125k and was rather new to me so i usually do that when i by an old used car. car started to stall when turning slowly so I had throttle body removed and cleaned at dealer for free. They told me my egr port and valve were clogged and told me to change the egr soon. A few months later I ordered it and the iac,cts,tps,pcv. hoping to fix it my self for under 200$. I just bought a house on the 10th, is why im low on funds to spend on Sh!t I dont need to. I have another car and a motorcycle. I just really like my grandmarquis. I figured someone on here would know what cause a car to run rough only when using ac/heat at idle or using 2 windows at once. I think that issue is also linked with the car stalling only when turning and slowing down. Its odd to me that it runs amazing with the ac or heat off or turning and slowing
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 21, 2020, 8:06 PM
Post #10 of 12
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Re: 1997 Mercury grand marquis random stalling and rough idle
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? Now you just said it does this with a high power use of windows and or a blower motor uses power. Check that voltage stays up to par during those times or it wouldn't run properly.
That should have been ruled out before parts tossing just takes time to watch it do that if normal that shouldn't allow low voltage to engine controls momentarily,
T
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lkmaryfla
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Jan 22, 2020, 9:52 AM
Post #11 of 12
(2330 views)
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Re: 1997 Mercury grand marquis random stalling and rough idle
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The voltage guage drops when i roll down 2 windows or use the ac/heat at idle.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 22, 2020, 11:24 AM
Post #12 of 12
(2324 views)
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Re: 1997 Mercury grand marquis random stalling and rough idle
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IDK if you have an RPM gauge but idle should hold same no matter what is on that LOADS engine normally. If just too low to hold UP voltage everything gets the wrong voltage confuses the whole show.
If you can make it drop below a real and witnessed 9V alternator isn't up to par or battery somehow so weak no momentary reserve for windows specially. Other things are meant to be totally powered by the alternator staying showing about 13v at the lowest and really not over 15v ever or will cause assorted problems up to a disaster if unharnessed over voltage outputs wrecks things.
Too Low = doesn't work properly. Too high it's overloaded big time or alternator no guts to keep up. Add just it needs realistic RPM as a given.
That being off would explain endless electrical gremlins nothing checked for features or operation is going to be correct until that is. Follow me?
Tom
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