Brand new here, Great Forum.

I have a '97 4.6 with 90k. Best vehicle I have ever owned. Original everything pretty much. Only things I have ever done besides regular oil changes and brakes is a coolant change, a couple of transmission fluid changes and maybe a couple fuel filters. The only problem I had was an engine light once, but after an EGR tube cleaning that I learned how to do here, (Thanks!)it was fixed. Runs perfect but gas mileage is is starting to decline.

Just wanted to get some ideas on what I should be replacing as far as a tune up is concerned. I've been reading alot here about possibly plugs and the 02 censors that could help with the mileage. What else should I be doing at this point?

 

Replace the plugs for sure, but be prepared for some fun. The plugs are very deep, and the ones toward the rear of the engine are hard to access. On my 97 4.6L, several wires would just not come off the plug, I had to tear them off in pieces... Take off as much as practical to give yourself access to the plugs (the intake plumbing), and I also found that disconnecting the injector electrical connectors helped.. The rear-most plug on the passenger side is the worst.. I ended up unbolting a large terminal block thing on the firewall that was in the way, and pushed it aside. Be careful not to crossthread the new plugs, and use dielectric grease on the wires where they connect to the plugs. You'll probably want to change the wires too, since any that get stuck may get destroyed anyway...

 

I found the spark plug boots the most difficult part of the spark plug replacing job at first until I realized each boot has a upper lip. Find some thin coarse string and place a slip knot under the lip, wrap other end of string around a screwdriver and then pull up. After using this method I stopped swearing and had all the boots off in minutes. The spark plug boots were usable, but decided to replace them since I do not plan on replacing the plugs for another 100,000 miles. I suggest the Motorcraft versions as well since they seemed best designed to not let moisture in the hole, otherwise you may experience cylinder misfire.

 

JBH tell us how you make out,what you had to use to replace the plugs(what tools,swivels,extensions,etc.) cause i have the same exact engine with 114,000miles and wanting to replace the plugs and wires,i looked at it before and said the same thing how in the h*ll do you get to the back/rear plugs???
thanks.

 

The rear plugs are not all that hard to change if you have the right # of extensions and universal joints. Given your mileage, the plugs may be hard to break loose, however.
I would also replace both coil packs, plug wires (use ONLY Motorcraft wires!!!), and oxygen sensors.

 

exactly i am no dummy. once i am in there i'll replace everything. but i am hesitant cause of the sparkplug situation,it looks like a "whole day" job replacing the plugs?, i'll just have to get off my butt and tear into it

 

Thanks for all the replies. I got the plugs changed today, not too bad. I bought one of those extended (5-1/2" long) plug sockets and it really helped alot. It gave me a better feel for the plug than using all those extensions and swivels. It still took me an hour or more. Worst part is the terrible back ache I now have!
Thanks again for the help!