2002 Escape Random Misfire, High Idle, and CAT prob fixed...
 

I've been reading and asking a lot of questions here, while working through the various issue in my 2002 Ford Escape 3.0 V6. over the last year. The help he saved me a lot of $$ I didn't have, and taught me a lot about the truck as well. I enjoy working on it, especially when I better understand how it functions. That's to everyone for your help, the info was invaluable.

First, I corrected a random misfire issue about a year ago with the help of this group. I had gotten water on the engine while washing it, and I found later that there were little hairline cracks in the coils. I damaged a couple of coils while driving it around like that. Thank goodness, I got on this group and discovered that driving with damaged coils are very dangerous to your ECU and your CATs. Thankfully, I downloaded the instructions, located the bad coils, changed the upper intake gaskets and bad coils, and got it running good again before I destroyed the ECU. I also had the common problem with the vacuum elbow collapsing on the large PCV line that connects to the back of the intake manifold. I replaced the flimsy & rotting elbow with a short piece of heater hose and shoved a copper 1/2" 45 degree elbow from the hardware store inside to hold the shape. Problem solved.

Next, as a result of driving around with a misfire, I damaged the CATs in the manifolds. I learned the hard way, these CATs don't like raw fuel dumped in them. These things are EXPENSIVE, so do yourself a favor if you have a random misfire... fix it fast before you ruin the CATs. Just go ahead and get a full set of coils, upper intake gaskets, the instructions on changing plugs from this site, and do it. Easy and cheap. So, being a tightwad, I gutted the cats in the manifolds, and removed the 3rd downstream CAT. WOW, my fuel economy shot up much higher than it had ever been...around 24 mpg. Naturally, that threw a CEL for the CAT failure. Over the next few months, I worked on a patch for that, and all is well. Also, this thing has a LOT more passing and pulling power like this...

Once everything was running great, I discovered I had an intermittent high idle that would come and go. I ignored it over the winter, but once it warmed up outside, I decided I needed to straighten the problem out. Initially, I swapped the IAC that I replaced a year ago when it began to stick and thought that was it, but it wasn't. I read a bunch and it seems like, more often than not, it's the gaskets on the lower intake manifold that are the culprit. Yesterday, I replaced the upper (again) & lower intake gaskets and all of the vacuum hoses (most of them were cracking and dry rotting, anyway). I tested the injectors while the lower manifold was off, for dripping/leaking with the ignition "on". All was well. I also installed a new set of coils I bought a while back and was waiting for the opportunity to do them, new PCV valve, cleaned the throttle body with the instructions from here (it was nasty and had the carbon buildup), tested the TPS, and installed new gaskets on the throttle body, EGR, and IAC. She runs like a new truck, now. The IAC is controlling just fine and it's idling at about 650 rpm. It looked like two of the gaskets on the bottom manifold were leaking, as the contact surface of them were dirty. 3 hours, start to finish, thanks to all the help and education here on the forum.

So, in summary, if you have a random misfire, don't beat around the bush. Replace the upper & lower manifold gaskets, coils, vacuum hoses, clean the throttle body, replace the PCV valve, the PCV elbow and insert a 1/2 copper 45 degree elbow in the PCV line that connected to the back of the intake manifold. It doesn't take that much time, is an easy job, and you'll waste a lot less time guessing at the problem.