Fuel flooding Cylinder #4 keeps flooding; change the EMC, flooding stopped and got excellent mileage for four days. Then the fuel flooding resurfaced at the same #4. Any idea, plz?

Connect a fuel pressure gauge to the fuel line and check the fuel pressure. If it exceeds manufacturers specifications; replace the fuel pressure regulator.
Spark plug cables which have aged, and now have more han 1,000 ohms resistance per inch of length, also can lead to cylinder flooding; and should be replaced.

Does it continue to flood the cylinder it it is unplugged from the harness ? ?
Could be a computer problem or a short in the wiring.

The size of the engine alone will not determine gas mileage. There are many other factors including vehicle weight, design of the motor, etc. So in answer to question 1, size isn't going to matter.

For question #2, make sure you change the oil, oil filter, air filter and keep the tires inflated to recommended specs. That might help you out a bit...

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Yes, This happens more and more. You can verify this wile your changing the injector by turning on the key after you pull the fuel rail (keeping the injectors on the rail).
Good job finding this. There are a lot of people that would over look this important factor.
Good Luck and God Bless.

Blown head gasket for sure if its a petrol engine.

If its diesel then its overfuelling.

well the first thing you should do is check the compression in cyl number four the compression should be within 5-8 of the nearest cyl if you see a significant diffrence in pressure you have a week cylinder...also is there any discoloration on the number 4 spark plug a coolant soaked or fuel soaked spark plug can lead u in the right direction..lastly i would take a look at the exact fuel pressure you will need a gauge and take a look low or high fuel pressure can cause a misfire....keep in mind that a clogged catylitic convertor can also cause a misfire do to accesive back pressure give your convertor a tap and see if its rattling ....hopefully this can lead u in the right direction ...good luck

Hi,
This is a broad spectrum of possibilities. I would first start with a simple approach of insuring good gas.
When these symptoms occur, get a bottle of fuel additive and add to your tank. Possibly you have some condensation issues. This could be just the ticket... I hope so. Good luck.

try the crankshaft sensor. it is on the transmission bell housing on the passenger side. You could also check for codes by turning the key to the on then off 3 times (DO NOT START THE ENGINE) and it will give you any stored codes in the mileage display

The PCV and the fuel filter replacements are not going to increase you fuel mileage. What you should really consider is getting some good fuel injection cleaner into the tank, and get an "induction system cleaning". Those two items alone will address most of your mileage issues. The PCV does nothing for mileage, nor does the fuel filter. Also, for maximum fuel mileage, you should have the correct sparkplugs from Toyota in your car. "Aftermarket" plugs doe not perform very well at all.

check the egr valve it sound to me that its stuck open and if this happens excessive exaust gases are flooding the intake or you might have a vacuum leak either one of these problems will make a high pitch sound