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Engine Stalls and Air Conditioning

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Matawan
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NJ
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What I Drive
2011 Ford Fiesta SE
#1
Hi Everyone- apologies if this is in a previous thread but I could not find the specific problem. My 2011 Fiesta SE Hatchback stalls out from time to time when I am slowing own to a stop, or when I have already stopped at a light. This problem only seems to occur when I have the air conditioning on and it is a hotter day. Now, I have a single code for an oxygen sensor not working properly (I am in the middle of fixing that but having a heck of a time freeing up the factory O2 sensor... I am not a particularly strong person and I do not often do this type of work so my coordination is not great for this type of work).
The other day, the car did not shut off, but as I was driving I lost all power, the pedal goes straight to the floor and the engine BARELY revved. Could the O2 sensor be the only problem there? I have no other codes, but it seems like something is just off. Any ideas?
 

scotman

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#2
I think the first thing to inspect is the air filter box. Are all the hoses tightly attached? Are there any cracks or splitting in them that might cause a vacuum leak?
Then I would look at the air filter element and the airflow meter in lid of the air box. Then If all that looks good, I would move to the throttle body and check out how gummed up or clean it is.
The upstream O2 sensor is not always a culprit in stalling issues. But, if it doesn't react to air/fuel ratio changes you would get a MIL lamp. My opinions are based on the information you provided. Once we get above 75k many strange things can happen. Many of them are electrical in nature.
 
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Thread Starter #3
I think the first thing to inspect is the air filter box. Are all the hoses tightly attached? Are there any cracks or splitting in them that might cause a vacuum leak?
Then I would look at the air filter element and the airflow meter in lid of the air box. Then If all that looks good, I would move to the throttle body and check out how gummed up or clean it is.
The upstream O2 sensor is not always a culprit in stalling issues. But, if it doesn't react to air/fuel ratio changes you would get a MIL lamp. My opinions are based on the information you provided. Once we get above 75k many strange things can happen. Many of them are electrical in nature.
Thank you for the advice and tips- I will check all of those immediately. I could not get the O2 sensor out so I am actually taking the car in to have my mechanic take care of it for me- kills me to have to turn the car over but other than tires I've never had to have anyone else work on the car since I bought it in 2012.
 
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NJ
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2011 Ford Fiesta SE
Thread Starter #4
I just had a terrible time with the car! Ugh, this is rough. I got two new codes pop up- P0068 MAP/MAF Throttle Position Correlation, and U0101 Lost Communication with TCM. Any thoughts?
Can I just clean the MAF sensor for the first one? Rough time for this to go down!
 

scotman

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#5
Hi. I don't understand why the TCM communication fail. Maybe a bad ground?
This image of the MAF harness is where I would be looking first. Broken wires, or connector not seated?
The TPS correlation code would explain the "no power even though the go pedal is on the floor" issue. It could be a failed TPS or it could be a failed ground to the TPS.
You need to get it to a mechanic.
 

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Handy Andy

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#6
MAF sensor? Wow, they are in the intake manifold as well as another problem area to check, your PCV valve.

IF you don't know where it is, and you have over 50K miles, then you should think about having it looked at...

MAFPCVValve.png

The PCV value itself can "plug" or weaken - making the engine consume oil or run rough. Can cause an air leak and even a check engine light.
  • Stalling with the AC on though - not uncommon, but if the engine has not had any work done to it a while - you might need to roll up your sleeves and look over your engine in a closer inspection.
Same applies to the MAF sensor - you'll need to TORX driver (T15 or T20) to remove it.

The PCV value uses a hose routed from it's valve located on the side of the engines' cylinder head on the intake side, INSIDE the serpentine of the intake manifold to and over by the MAF sensor.

IF you have a stalling issue this part of the intake manifold house the MAF senor as well as the vapors from the engines' crankcase flow into here - so it's not out of the realm of possibilities that you may have some dirt and gum and varnish in there, this may be the area you need to clean out.

Start with the MAF sensor - a simple automotive emission senor cleaner spray should help you with that MAF sensor.

The PCV valve? Requires some disassembly - you need to at least gain access to the PCV valve. That may mean you have to remove the intake manifold to do this. In the photo, it's behind the hose.

If I knew of a simpler way I'd tell you, but taking apart the engine's intake manifold may be your only option. There is a "plate" that the PCV value seats into - this plate has a seal to keep it oil and air tight The engine gathers fresh air from the airbox off to the right in the photo and you can even see the hose routing into the top of the valve cover - that hose - you can pull off and cover the valve cover side of it with your finger - carefully - usual disclaimers HOT engine parts and moving equipment - and see if a vacuum can be formed by plugging the hole with your finger while the engine idles. The longer it takes to form a vacuum, may indicate leaks or the PCV valve assembly is not airtight. IF you see oil where the hose routes to the side of the engine - this usually means the hose or the plate seal has failed and needs service.

The PCV valve may need replacing - it's not impossible but if someone knows an easier way to fish it out of the intake manifold without having to tear apart the motor to do it - I'm all for it and would like them to post the procedure here to help the rest of us.

The PCV valve issue arises when the MAF sensor or Throttle Position sensor inside the throttle body - fails. The engine doesn't rev up because the throttle body can't move, or it's plugged from gunk caused by the PCV valve sticking open and flooding the intake manifold with oil and foul air - making the MAF sensor or MAP sensor fail - then you have a bigger problem.

You would also notice smoke and the odors of burning oil.

The 2011 issue sounds like a series of cascading failures related to throttle body and MAF - O2? That becomes the related part when the throttle body or it's gasket to the intake - fails or starts to come apart. again, can be related to age of hoses and the seals starting to fail.

1669335230862.png
You have to gain access to the Positive cable connections...so you can inspect and
clean out any corrosion or fix loose cables.
1669336243517.png
Positive post terminals and
1669336300922.png
Battery returns too - Behind the battery on the engine firewall.​

TCM? That more than likely is a Battery power or ground cable issue back at the battery - the red cover for the Positive post has a series of bolt on fuse links and connectors - so if these are getting too badly corroded - they can make intermittent connections - so try to pry off that red cover and see if the wires are properly seated and the bolts are tight and not corroded.
 
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