ok so my 97 f150 5.4 started missing on 5,6 it had antifreeze on top of the spark plugs but i cant figure out where its coming from my truck has been loosing coolant and it seems like the system is holding pressure because every time i take the cap off the radiator overfill i can hear it hissing then i see the antifreeze level plummet there's no visible leaks that i have seen when the truck is running an missing it steams out the exhaust but when its no missing it doesn't seem to be there's no milky oil or anything the thermostat doesn't seem to be leaking either the truck has over heated a couple times due to the antifreeze disappearing or the temp wont move at all then it shoots all the way to hot and cools down within seconds to normal i just put a new thermostat in as well no help there ethier

also it sometimes misses on 4 and my exhaust smells like straight gas i put 4 gallons in it got 29 miles out of it

thanks in advance guys any input would be helpful because im totally lost

 

Mine is doing exactly the same thing except mine is just on cylinder one. I have spent plenty of money fixing this and that or at least what I thought was wrong with it. It is the intake gasket come to fine out. Mine doesn't show signs of losing water or anything bad and mine also holds pressure. I was told it has to do with the motor getting hot and stuff like that makes it lose coolant. I am having my intake gasket changed this week. I am also checking the intake while I have it off to make sure there are no cracks or anything in it. I would say yours is doing the same thing.

 

Coolant on top of plugs . In the plug port is not a head gasket . 5-6 are driver side 1st and 2nd plug .Known for intake leaks .As are 1 & 2 plugs on pass side . If coolant is on top of plugs , Intake or hose leak . IF IN CYL. ON PLUG ELECTRODE , ON TOP OF PISTON , POSSIBLE HEAD GASKET LEAK ,OR INTAKE LEAK . If the intake gasket blows , it can put coolant into the cyl through the intake valve . That usually causes a hydro lock and or a bent rod .

 

Mine is coolant on top of plugs in the plug port. I finally took it to a guy this past weekend that I had heard about from someone and he didn't even raise the hood. I just told him the symptoms and what was going on and that's what he told me was going on. Im changing the intake gasket this weekend on mine.

 

If coolant is on #3&4 plugs ck heater hose connections . They were an issue in the past . Some now .

 

Mine is on cylinder one. I have heard sometimes if its on the back plugs that possibly the cowl is leaking and letting water run down on them. when mine gets a lot of water on it and it starts missing I was having to take the coil out and the plug and leave the plug out and start the engine and let it blow that crap out and put it all back together and then it would miss for a few miles then stop. But as soon as it fills back up enough to make it misfire again I have to do the same thing and I could not figure it out until this weekend, when that guy told me the intake was leaking. Also when it starts the misfire it throws codes for o2 sensors on that side and I thought all of them were going bad so I changed all four and still had them reading bad. So I figure with an intake leak that it's getting to much air and causing them to have bad readings. I hope once I change that gasket that that will take care of all of it.

 

Change your coil boots if they have been wet . Heck , change them anyway for maint. if not recently changed .Would be a good time for plugs also if not recently changed . Make sure to blow out any debris from the plug wells before intake or plug removal . For that matter , blow all debris from intake and head area before intake removal .

 

When i change the intake I will make sure i blow off everything. I have put two sets of plugs in it in two months because i have gotten bad plugs before so that was one of the first things i changed. I will get all new boots when i change that intake gasket.

 

Does.yall steam out the exhaust.somtimes? And.i.hope.its a bad intake gasket because i have a waranty.for.that my engine only has 6000 miles on.the.rebuild

 

mine does a little bit but not real bad. last time I had one that blew a head gasket it steamed real bad out of the exhaust so bad you couldn't see behind yourself. It depends on where the gasket has blown at. I would change those intake gaskets and see if that fixes it. They are only like 35 dollars for a new set and then whatever your mechanic charges to do the job. Mine is charging me 40 dollars to change them.

 

I'm having a similar issue on my '98 F150 with a 4.2/auto. Coolant disappeared, no heat, but the dipstick shows no contamination of the engine oil. It had to go somewhere...