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1995 Mercury Cougar with a weird Idle


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65Plyman
Novice

Nov 26, 2018, 3:37 PM

Post #1 of 18 (323 views)
  post locked   1995 Mercury Cougar with a weird Idle  

Hello all,


Just a few days ago I started to notice a strange idle on my 1995 Mercury Cougar XLR (4.6L V8). It is normally at around 800 RPM but every 10 seconds or so it surges up to 1400 (see video below). I also noticed that this only happens when the A/C and/or heat/defrost are on. It doesn't happen at all when the entire climate control system is turned off. When I'm driving I don't notice it, nor when it is in gear at a red light. I have asked several mechanically inclined friends and they are stumped.
Things I have recently replaced on the car: brakes, front-end rebuild, alternator, plugs, wires, and timing chain. All between 2 and 3 months ago.


Video showing what happens:
https://www.youtube.com/...amp;feature=youtu.be


(This post was edited by 65Plyman on Nov 26, 2018, 3:37 PM)


Hammer Time
Ultimate Carjunky / Moderator
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Nov 26, 2018, 4:34 PM

Post #2 of 18 (317 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

This is not uncommon at all, especially on Fords.

The AC compressor cycles on and off normally which puts a load on the engine when this happens. The IAC is supposed to instantly respond by bring the idle back up to keep it steady but it's sticking and having to make larger adjustments.




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.



(This post was edited by Hammer Time on Nov 26, 2018, 4:36 PM)


Tom Greenleaf
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Nov 26, 2018, 10:04 PM

Post #3 of 18 (293 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

Do as Hammer Time said but this might be normal for this vintage now! Eeek - 24 years old. Pre OBDII no problem just as said it's trying to cover load of compressor that will NOT stay engaged if cool/cold for long just cycles.


Have you owned this with seasonal changes before and noticed it? I do or did with these they got over it in a while. You do have to be a team player with caring for an older/OLD car now and can if you are up to it.


Not many left now if handy and pay attention if all test out and cleans up as normal and do for one of my own not used much just unplug LPCO for "off season" and remember to allow it to run on a warmer day now and then thru Winter as it circulates oil for the A/C and defeat it again it may last for you.


Guess on the A/C part. It plenty old enough the "Spring Lock" connectors and compressor shaft seal don't like cold and leak but don't in season? Take your pick with that either check and fix which IMO wont last anyway or get used to checking A/C out early for next season put that on a list of keeping it going does require some real A/C know how tweak it back up as needed takes real KNOW HOW or put up with for the days with wild temperature swings it will quit it later or should?




T



Hammer Time
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Nov 27, 2018, 5:34 AM

Post #4 of 18 (285 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

If this IAC system is working properly, you won't notice any idle speed changes.



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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.



65Plyman
Novice

Nov 27, 2018, 11:24 AM

Post #5 of 18 (277 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

Thanks guys, I will look into checking the IAC and cleaning the throttle body. So would that explain why it only happens when the climate control is turned on? It happens when the heater and/or defroster is on too so that's why I'm wondering it might not be an A/C specific issue.


Hammer Time
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Nov 27, 2018, 11:27 AM

Post #6 of 18 (271 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

I thought I explained that. The AC compressor coming on and off, which is normal, prompts for an idle speed change that the IAC is not keeping up with.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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.



65Plyman
Novice

Nov 27, 2018, 11:30 AM

Post #7 of 18 (267 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

Ah, forgive my ignorance. I thought that the A/C compressor wasn't used for when I am just running the heat and defroster. That would explain why it does it when I use both A/C and heat.


Tom Greenleaf
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Nov 27, 2018, 11:34 AM

Post #8 of 18 (267 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

Can't know which dash controls you have exactly. Most will also allow A/C compressor to come on except if you have an "economy" choice or plain "heat only" thru only floor vents. That's on purpose the idea is exercise the compressor OFF season some will say helps defog/dehumidify air which is bull IMO. It will shut off if cool/cold just because on the low pressure is too low it's supposed to shut off confuses it for a while.
Almost everything does this and you don't notice even this car. I do in my own more often just heat of engine when shut down heats up engine area the A/C thinks it's OK to run. Sorry for the $50 explanation but that's why. Noticing it even I do but it quits it quickly if cold out - real cold or don't at all.
Other: Funny you mention it tech and all WE don't drive every vehicle in all conditions a lot to know all quirks that are normal to each model or a real problem. Could be IAC no harm in cleaning it and checking for vacuum leaks already said by Hammer,


Tom



Tom Greenleaf
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Nov 27, 2018, 11:37 AM

Post #9 of 18 (263 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

Again: It runs to circulate lube is good for it AND will claim in certain conditions like humid fog the cool air would dry first then be heated work better. I said BULL as refrigerant can't run when that cold it could choke compressor so shuts off.
The car is simply adjusting idle for the load expected and you notice it - most you don't,


Tom



Hammer Time
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Nov 27, 2018, 11:46 AM

Post #10 of 18 (257 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

The AC removes moisture from the air so most cars are wired to run the compressor in both defrost and AC positions. That doesn't effect the air temp controls.



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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.



65Plyman
Novice

Nov 27, 2018, 11:56 AM

Post #11 of 18 (251 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

Thanks guys, I use me car for Uber so that is why I noticed it because I sit at idle a lot waiting on customers. I'll work on it tonight and get back to you.


Hammer Time
Ultimate Carjunky / Moderator
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Nov 27, 2018, 12:01 PM

Post #12 of 18 (247 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

If it seems to be cycling too frequently, it may be low on refrigerant also.



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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.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Nov 27, 2018, 1:08 PM

Post #13 of 18 (234 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

Uber use! Yes and plenty of engine heat idling to EXPAND low refrigerant would make it come on. This is your warning to save it from self destruction over off season and you must be assertive. You can just unplug the two wire switch (passenger's side) on what was a black or silver round can called an accumulator and compressor can't come on but do tie it well out of harm's way.


Now go get the car leak checked even this time of year and performance of A/C difficult if not really working hard. See - oil circulates but requires the charge up to near perfect to do so or just sits and a pump of most anything can't operate dry! It kills itself, leaks out totally so will not come on but you don't notice till you need A/C again.
Just me - sorry but if you do a ton of driving in an old car like this save the thing or will cost a fortune to fix later if still a good serviceable car. That wouldn't be a good suggestion unless you also allow it to work now and then thru off season.
AYOR if you don't understand don't but if you can you'll win. NO JOKE AND A/C CERTIFIED UP THE BUTT NEVER ONCE REPLACED A COMPRESSOR IN ONE OF MY OWN VEHICLES NONE NEWER THAN 22 YEARS OLD.
Depends too: Mine know leak if exposed to below 20F or so outdoors in wind thru shaft seals do not expand and contract the same as the bushings when older or miles.
IMO again. That's the #1 reason compressors just burn up and ruin the systems at this point, this car nothing is going to come apart it will all bust so a horror to redo whole system.


Your call if you wish to be that assertive unless it's too late already that's highly likely it's just low and normal at the age to lose some just not easy to DIY dealing with when it will be warmer I call that "tweaking" it back to spec most shops wouldn't take the time - find out now and know now,


Tom



65Plyman
Novice

Nov 28, 2018, 12:18 PM

Post #14 of 18 (215 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

Well, it wasn't any of those suggestions. As I opened the hood last night, I noticed the battery cables were pretty acid covered. So I cleaned them, and now I haven't had the issue since. As far as I can figure the A/C probably wasn't getting a good enough connection from the battery and so was compensating by revving the motor.

Thanks Again!


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 28, 2018, 4:01 PM

Post #15 of 18 (209 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

? It will be back you just reset everything to a base even pre-OBDII. Let it go for a while and for sure clean connection always matter and lack of corrosion. Just one thing is if it went without notice that long (how long since last new battery?) it's time to check it and charging system works properly anything would be erratic with improper operating voltages,


T



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 28, 2018, 5:09 PM

Post #16 of 18 (206 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

LOL.......... don't bet on it.

When you disconnected the battery you reset all the learned memory. The problem will be back.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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.



65Plyman
Novice

Dec 5, 2018, 12:06 PM

Post #17 of 18 (172 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

Well, it has been a week since I last touched it and it still isn't doing it anymore. Idles just fine now, I can still hear when the compressor kicks in, but no big bump in the idle.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 5, 2018, 2:20 PM

Post #18 of 18 (166 views)
  post locked   Re: 1995 Mercury Cougar with a weird Idle  

OK, I'll close this now.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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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