Oaky, I thought too deep into this, and confused myself totally now.

If there is major vacuum leaks, letting unmonitored air into an FI engine. Will that cause the engine to run hotter than normal?

 

Generally, no.
The cooling system should be self regulating, you most likely have a cooling system problem. When is it running hotter than normal, at idle or while moving? Based on the asnwer to that question, you could have a bad thermostat, bad fan/fan switch/fan wiring, or maybe just a bad sending unit for your temp gauge. Or, it could be something as simple as low coolant or an air pocket in the cooling system somewhere. Or, you may have scale or some kind of buildup in the radiator, or too much fin corrosion.

You haven't said anything about what car, what engine, if you're in the middle of doing a swap, turbo kit, or other major changes, etc., or if you just bought the car and you're finding this out now. You also haven't clarified if you mean 'fuel injected' or 'forced induction' when you said "FI".

 

fi= fuel injection
Its on my 92 4cyl rodeo, 2600cc, w/ fan/clutch fan cooling.
the truck used to overheat while at idel or in traffic, usually after 45min of use on any condition of driving. With new h20 pump, and stat.
Well its been sitting for over 2yrs now, I thought it maybe a bad head gasket or even a cracked head.
Today I started it, fixed a bunch of vac leaks, and put Redline water wetter in it. let it idle for 1hr45min, and no boil-over like before. ( I know water wetter isnt that good).
I am going to pul the head off this week and get it all chked out too.
I WAS JUST OVER THINKING, and thought that unmetered air would cause, overheating due to unequal amounts of fuel not being added to the combustion chamer. ( I over thought the entire thing), it got tto be a bad gaset or head, but there are no signs of them being bad.

BTW, I was on the 97 NCSU A&T Baja SAE team.

 

Unmetered air would cause stuff like poor fuel consumption, and poor perfomance and maybe hesitation. Over heating usually can be traced back to thermostat or a possible blockage. Maybe a hole in the rad or air getting into the system.

Example, I had a stock 93 240 with that stop leak raditor stuff in it. I dumped the Anti-freeze and flushed the system. Replaced the thermostat and it worked till the raditor connection piece broke and dumped the water into the engine bay and on the ground. I replaced the rad and all was normal.

Start simple. then go for the big stuff. If the head gasket is toast your not gonna save your self any more money by going straight for the head. Since it' been sitting that stuff should be replaced anyways.

 

Just to add, the air will only be unmetered if there is a MAF instead of a MAP sensor, and even then the O2 sensor will correct for a lot of that air.. It def sounds like you have bigger problems than unmetered air.

 

thanks all. I wish the truck would blow out a gasket, and smoke everywhere. then i will be sure its the head gasket. Otherwise Its just wishful thinking its something else causing the symtoms.
thanks to all.