2001 Expedition with 4.6.

Full disclosure:

I just finished replacing the heater core, A/C evaporator, A/C dryer, and blend door. While doing this job I disconnected the 3 wiring harnesses above the A/C dryer. Some coolant also splashed on top of the engine while I was messing with the heater hoses.

I planned on doing the fuel pump next because it has started acting up with the pump not turning on when you try to start the motor. After a few hits of the key the pump will start up but I know full failure is coming.

I got everything back together and drove a short distance to the store. It ran fine until the trip home when it developed a pretty strong, but intermittent miss. Now it runs smooth at first but the further it is driven the worse the miss gets. It stumbles worse under load. It feels like an ignition miss and the converters are really smelling when the miss is really hitting. At idle the miss is intermittent.

I pulled the coils on 1-4 thinking mabey coolant got down in the spark plug holes but they were all dry. I took the electrical connections apart to make sure I didn't damage anything there and everything looks good. I don't see any obvious vacuum leaks.

Logic tells me I messed something up when replacing the HVAC items but for the life of me I don't can't figure it out. I went through and started disconnecting coils with the motor running but couldn't narrow down where the problem is....especially since this is intermittent.

NO CODES!

Can someone steer me in the right direction before I start blindly throwing cash at this thing starting with all new coils?

 

Drove the truck around quite a bit hoping it would throw a code. No dice.

The miss came and went. It seemed to show up the worst after short cruises at a maintained speed, then turn a corner onto a side street and try to go down the street. At the end of my driving it was pretty bad the whole time.

I eyeballed all of the vacuum lines and don't see any problems.

I guess the next thing to do is go old school and pull all the plugs to see if they can tell me something the computer is not.

I'm still hoping for suggestions and guidance.

 

When you spilled coolant on the engine any chance a significant amount leaked into any of the spark plug wells?

 

Have actually checked for codes? Just because the check engine light isn't on doesn't mean there are no codes.

 

I pulled the COP's on 1-4, where the coolant spilled, and all the plug holes were dry.

My hand held scanner says "no codes".

 

Or you could go even OLDER school and tape the fuel pressure gauge to the windshield and see what the FP is when it gets to missing.

 

Haaaa. Yeah, that crossed my mind as well.

I pulled the plugs on 1 through 4 and checked them out. Plug #3 stunk of coolant, even on the electrode side, and the threads were wet enough to leave residue on my work bench. I'm gonna guess that is the culprit.

I will replace all 4 plugs on that side since I have them out and mabey throw a new coil on #3 for good measure.

I'll report back with the results.

 

You called it alloro. I put new plugs in cylinders 1 through 4 and it is running like a top so far. I did NOT replace the coil, just the plugs.

Apparently there was just enough coolant in the #3 hole to not reach the tip of the coil but be enough to leak down the threads of the plug to foul the combustion i n that cylinder.

Thanks for everyone's help!