Reddit reviews CRC 05110 Mass Air Flow Sensor Cleaner - 11 Wt Oz.

> is having the hose unplugged the same thing?

More or less. Disconnecting the air intake means no flow through the MAF. The computer takes that to mean that the sensor has failed and runs the default fuel maps.

You can try using something like CRC MAF Cleaner, but if the problem has gotten bad enough to cause stalling the MAF probably needs to be replaced.

I just cleaned em with some MAF Sensor Cleaner spray like this stuff here.

I saw a nice MPG improvement (~2mpg) from this, but changing my spark plugs (and properly gapping them) really was the biggest improvement.

Things to check for fuel economy -

• Your Tire pressure (I set mine at 36psi - COLD) - The ride is a little harsh but it helps with less rolling resistance.
  
  
• Your right foot - I know this may seem like common sense but "Jack rabbit" starts should be avoided and abrupt acceleration as well.
  
  
• Proper braking - Don't use the brakes if you can help it, leave a cushion of space between you and the car in front of you so you don't have to waste energy pressing on the gas again after slamming on your brakes.
  
  
• Maintenance (This is the big one) - Your 2.3L Duratec comes with a "Lifetime Air filter" unfortunately the whole air box will need to be replaced if your Focus has over 150K on it or the filter is clogged / dirty. CHECK YOUR FILTER MINDER WITH THE ENGINE RUNNING. If it is bad it can cost 4-$500.00 to replace. I would suggest getting an intake system on ebay or amazon (K&N, AEM, etc.) and replacing the OEM air filter / box if the filter is clogged or dirty. It is substantially cheaper than the factory air box / filter combo if you need to replace it.
  
  
• Oil level / Type - be sure to run the recommended 5W-20 Synthetic or Synthetic blend oils ONLY and be sure it is at the "full" level on the dipstick. If you took it to a Jiffy lube, Walmart or any quick lube chances are they used a conventional 5w-30 and it WILL have an effect on fuel economy.
  
  
• Rear brakes (Some models of Foci have rear disc brakes, if you have a traction control button on the center console next to the e-brake you do not need to follow this step) Check that they are not dragging and adjust them if they are, check the E-brake to be sure that it is properly adjusted and not engaging the rear brakes as well.
  
  
• Spark plugs - Pull one out and look to see if they are in need of replacement, you can find a good guide to spark plug replacement HERE.
  
  
• /u/verbthatnoun suggested a MAF sensor from a bone yard, he's on to something here but you can clean the sensor and restore it's output if it is dirty. I wouldn't trust a MAF from a junkyard due to the environment they are typically in, also a low output MAF will cause a check engine light but only when it gets to a certain point.
  
  If I think of anything else I'll add it here.

I had a similar issue with my 2010 lancer.

my car would idle low & struggle to stay on.

It died twice while I was reverse parking.

I cleaned the mass air flow sensor with this but its too early to tell if that did anything.

Also found this video, hope it helps.

Those IATs don't sound that far out of line. 130°F to 150°F is pretty common after it's been parked a bit, or in stop and go traffic. When running 10 miles or more at highway speed, it should drop down and approach outside air temperature. The only "outlier" in your list is at startup in the morning. IAT should be very close to outside air temperature if the thing has been sitting overnight.

If your fuel trims are running consitently negative, you might want to clean the wire in the MAF sensor. Use MAF sensor cleaner on that. Spray it on the wire pretty heavily. Let the stuff drip off. Any that remains should fully dry (only takes a few minutes) before you apply power to the MAF. If you have to wipe off any that drips off and puddles in the housing, use a paper towel or clean rag and don't touch the "hot wire" in the sensor. There's a special cleaner for this part. I use CRC MAF Sensor Cleaner. amzn.com/B000J19XSA/ is one source, but it's available locally at most FLAPSs.

The PCM uses engine coolant temperature and intake air temperatures combined when determining mixture maps. The weighting to each depends on throttle position. Below about 20% throttle opening, it's weighted 100% to engine coolant temperature and intake air temperature is ignored. Above 80% throttle opening, it's weighted 100% to intake air temperature and coolant temperature is ignored. In between, its a sliding scale, the wider the throttle opening, the more IAT is weighted and the less ECT is weighted in the calculations.

I would recommend cleaning the maf sensor with a maf specific cleaner

EDIT: https://www.amazon.com/dp/B000J19XSA/ref=cm_sw_r_cp_awd_y0SHwbC48FV82 this is the one product I would recommend

I'm still experimenting with different lubricants and cleaning sprays but the best so far:

1. No spray cleaning or lubricant works as well as taking it apart, completely cleaning it and lubricating it. Dust gums up oil. If you can afford to pay a professional to clean and service your typewriter, do so, the difference in the action of the keys is phenomenal.
   
   
2. I bought a Super Silent with sticky keys off E-bay and fixed it with these two products. Mass Air Flow sensor cleaner, and Dry Lube. Use the spray cleaner to clean out as much gunk as you can and the the spray lube to get things slippery again. (It takes a couple of sprayings combined with moving everything you want lubricated.)
   
   Dry Lube is spray Teflon that does not attract dust. This solution worked but does not completely clean out all the dust or make the action like new.
   
   I am presently disassembling my Super Silent and after properly cleaning it, I will experiment with various oils, PTFE(Teflon), and wax/ceramic lubricants and compare how they affect the action of the keys.
   
   For all parts other than the keys I am already convinced that dry lube is a better solution than any oil because not only doesn't it attract dust but you can blow out any dust with compressed air.
   
   
   
   

For the rough idle, clean the mass airflow sensor. This fixed it every time: https://www.amazon.com/CRC-05110-Mass-Sensor-Cleaner/dp/B000J19XSA/ref=sr_1_1?keywords=maf+cleaner&qid=1549668234&sr=8-1

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Best bet: https://www.amazon.com/CRC-05110-Mass-Sensor-Cleaner/dp/B000J19XSA

Dries faster than rubbing alcohol, safe to plastics and cleans thoroughly. https://www.youtube.com/watch?v=cLnDxM4O_eg