slow coolant leak, and random miss/weak fire.

[zerodevil]

Hey Yall.

I have a 2008 LTD with the 4.6L 3v. Recently discovered I have a slow coolant leak somewhere, that I have thusfar not been able to locate. there is no obvious puddling, or wet spots inside of the engine bay. There is no Coolant in the Oil, and no oil in the coolant, so fairly safe to rule out head gasket issues. My larger issue is that I have a completely random misfire/weak fire. Its not enough for the truck to turn on the CEL and give me a code. Truck will be 100% fine for 20-30 minutes, and then start sputtering/missing/lurching for awhile. Also appears to not care if the truck is warm or cold. Did Coils and Plugs a little over a year and a half ago, all motorcraft, all done per the manual. I'll pull the coils and check them with my meter tomorrow at some point.

In the meantime I was wondering if these 3v engines are known to have intake manifold gasket issues? Any other known trouble areas to look at?

 

[94Eddie]

I had a coolant leak issue recently and it was the radiator. This is a common issue with 3V 4.6L engines and the place where the leaks occur are hard to spot. Many times you won't see any obvious drips. If you do replace the radiator you might want to replace the water pump, hoses and thermostat if you have over 100k miles on you Explorer. These things are easy and inexpensive to replace with a radiator swap.

I was going to say the misfire sounds like a classic coil issue but if you have replaced them recently then it might be plugs or ignition wires. I have also read where water can pool in certain plug wells and cause misfires. My experience with bad coils is that it has taken a long time for them to register a code. They have to be close to the point of complete failure before this occurs.

 

[zerodevil]

Just wanted to update.

Coils and plugs were solid. The truck continued to randomly have random misfires and produced no codes for another 2 or 3 days after I pulled the coils/plugs for testing. And then cleared up on it's own. I suspect there may have been some water in the fuel. The truck had been parked outside in the cold with a 1/4 tank of fuel since November. Its been more than a week since she has acted up. Cheapest fix ever.

The coolant leak still eludes me, but I will wait till it is warmer outside, or the leak gets worse, before going ham on finding it.

Thanks for the help!