I have an 97 F150 with the 4.6 engine. A few weeks ago, I had a problem with the engine missing a bit, especially when pulling a pop-up camper, with a pretty good load of gear in the bed also.

Ok, I changed the plugs, using Motorcraft Platinum. I still had a problem, so after dark I check the wires. That was kinda cool following the spark around the engine. Replaced and all seemed well for a couple of weeks.

I get in the truck and start towards the city, and the truck starts missing badly. I stopped, checked to see if a plug wire had popped off, but nothing was amiss. After a couple of miles, it started running smoothly again. Wierd.

Three days ago, it came back with a vengeance. I checked plugs, wires, injectors, cleaned the MAF sensor, and nothing was coming up. I was going to check the EGR today, but the daggoned truck is running great again!

I am wondering what to try or look for when it happens again, because I am sure it will. I'd hate to be towing the camper to the lake and this starts up again.

 

On the 97 there is a heater hose and tube at the passenger side rear of the intake. It is very common for that tube /hose connection to leak coolant and it drips right down onto #4 sparkplug boot causing a miss on that cyl. Remove the boot and check for any coolant in the plug well or around the boot. Then dry it and install two hose clamps on the connection. Cyl #7 seems to get water in it's plug well from rain or washing the engine. Don't wash your engine using a hose or car wash. A miss under load could also be a coil. The vacum line hose right behind the throttle body, between the TB and firewall tends to crack at the elbow and cause a vac leak as well. A few things to check out. If none of those are the problem let us know. Take care

 

That will give me something to check in the morning. I know there is no coolant leak on #4, because I had that boot out several times since the problem seemed to be on that side. However, I will need to check #7.

Thanks!

 

What kind of plug wires did you use? Not all aftermarket wires will work well, and one or more may look secure but are not fully snapped down onto the plugs. Did you use dielectric grease in the boots at both ends? Your coil packs could also be on their way out.

 

I bought Motorcraft wires, and no, I did not use dielectric grease on the ends. I forgot to get a packet.

Can coil packs be tested? And, is buying a hand-held code grabber worth the money? I think they are about $35.

 

Coil packs can only be easily tested if you get a CEL with specific cylinder miss codes - you can swap the 2 packs and see if the miss changes cylinders. You CAN unbolt them and inspect them carefully for cracks and carbon tracks.

I keep meaning to get a cheap code reader, but Autozone pulls codes free.

 

Well, the truck is still running great. I think cleaning the MAF sensor did it some good. However, I don't think that was related to the original problem with the miss. I reckon I'm in for some waiting until it does it again.

 

Ok - it did it again. This time I jumped in the truck to go to work, and the miss started about a mile down the road. This morning, we had a severe storm roll through the area that dumped a crap-pot load of rain and some 60+ mph winds. If I remember correctly, we had a storm the last time I had this problem. Now to figure out where the moisture is getting in.

 

Have you greased the wire boots at both ends yet?

FYI, my V6 did much the same thing a couple years ago - missing after a rainstorm - and it was the coil pack.

 

Also, your hood seal is leaking most likely. Look for a split in the rubber or maybe it's just a matter of oiling it down. You could have leaves or a small branch stuck there as well.