Ive got a 2005, 3.0L, 5spd manual, Ranger Edge. Every now and then, after longer drives, the engine goes nuts with high rpms. Slowing down, I downshift, and when i push the clutch in, the engine revs up and then stays rev'd all the way down to 2nd gear. If I i stop and turn the engine off, it doesn't want to start again.

MAF has been replaced. Throttle position sensor has been replaced.

 

Welcome to the forum

The computer controls engine RPMs, once your foot is off the gas pedal, by opening and closing the IAC Valve, the Idle Air Control Valve
It looks like a can on its side on the upper intake manifold near the throttle plate

How to clean it seen here: https://www.explorerforum.com/forums...-w-pics.84220/

Once you have it off, plug in its 2 wire connector
Turn key ON, engine OFF
Look inside, IAC Valve should be open all the way
Unplug the 2 wire connector and it will close, spring closes it
It only moves 3/8's inch so not that much, but does MOVE
Plug wires back in and it will open all the way again
Repeat this as much as you need to make sure it is working

Do you use the Cruise Control on longer trips?
It's cable on the throttle could be sticking, hold throttle open a bit

 

Thanks. I will check the IAC as you described. That is about the only thing I have not checked or replaced. I do not have cruise. I do get a "misfire" on #6 frequently also. I've done a compression test and #6 was down to 90lbs. After squirting a little WD40 in and doing the test again, it shot up to 150lbs. So, it's rings. However, I don't think that has anything to do with the high rpm issue, though it does make the idle a little rough.

 

My rpm would jump all over the place and act like it was driving itself and for no reason what so ever would rev up to 4000 rpm until I would either use the clutch and higher gear to lug engine or just turn off engine and re crank which would fix the problem for a few minutes but finally after many months it got to the point where it did it all the time and I go so sick and tired of dealing with it and spent a lot of money changing this and that and I mean everything all sensors the throttle body 5 diff mechanics. Long story short if you have this truck and this seems to be a more or less common problem with the erratic revs and sticking rpm and truck trying to drive itself, I spent almost a year on and off asking around changing out all the parts,
my truck is a 2002 with today only has 38,000 miles on it and had only 33,500 when this problem started one day so after no one including myself could fix this issue not even ford could fix it and the forums had no definitive fix, so I just said screw it I unplugged the IAC and just drove the truck like that and have to say got amazing gas mileage and lots more power, but I’m a perfectionist and could not stand that the truck had an issue that for whatever reason no one knew how to fix it, so one day I’m driving the truck and I pass by a mechanic shop and said what the hell might as well stopped by talked to the mechanic and told him everything that has been done and replaced including two IAC one from oreillys and one from advance. Well this mechanic was scratching his head as well and said well let me and my helper take it for a test drive with their computer plugged in to it and see what it’s acfsully doing, once they got back and showed me the data it showed that the IAC was still reading some slight voltage when no throttle was being given and it was very minor amounts off but was just enough to make the computer think it needed throttle when it actually did not, he said go to ford and buy a official ford motor craft IAC and install that and reset the computer and I’ll be damned 2000 bucks and a year of wasted time and all it needed was a part that I’ve have replaced twice already, now with this I’m not knocking aftermarket parts and in most cases they work as well if. It better than the actual manufacturer part, I mainly use aftermarket on all my cars trucks motorcycles and even my show car my thunderbird and never had an issue. So sorry for this long write up just figured it someone and from reading and googling this issue there are a lot of people out there that have this same issue and it’s a bad and extremely not safe issue to have since the truck will rev and drive itself, so before paying mechanics and replacing throttle cables and throttle bodies and every sensor that truck has, just go to your local for dealer and tell them you need the actual ford motor craft IAC for your year model ranger and I almost promise you the moment you take off your old one and out the new one on the instant you plug it in your truck will immediately return to normal idle, I hope this helps and saves you lots of money and headache, thanks So now my question is my truck is an 02 and I love to do preventative routine Maintence my truck has right now like a little over 40,000 miles on it and I am wanting to replace the plugs and wires and ignition box can anyone guide me as to what is the best of the best to use in this application mainly doing it cause I just want to and if I happen to pick up a little performance along the way then great and thanks in advance for any help