Ive got an 04 ranger with automatic trans, I was on a long trip last week and noticed My gas milage was just awful. I was getting like 12mpg on the highway and she was getting close to 26mpg before last year.
She has 71k miles and I cleaned the IAC last year and also replaced the plugs and wires about 20k miles ago.
While in Fla My check eng light came on and she started to shake, thought maybe bad gas so I stoped and disconed the bat for 30 min and ate lunch. Drove back to NC and had its codes red at advance. Said misfire on #4 and misfire at idle on #4. Changed all the plugs again and Checked wires with ohm meter and all was good, reset ECU and still the same shake. Seems to run fine, but no idea what it could be any help is much apreciated.
Mike

 

Took My truck to the dealer today and it turned out to be a faulty injector on #4, getting replaced with the fuel filter, Compresion was 150 on all cyclinders.
Thanks Mike

 

Well picked up My truck tonight and what do You know I still have the same problem the only differance is that My wallet is lighter now.
They changed the #4 injector and also the fuel filter and She is still sick, guess I will call them again in the morning.

 

injector cleaner and high octance for a tank would have freed it up. Fuel filter isnt hard to do.

 

Well the newest update, Still not fixed. Today I swaped out coil packs and nothing also rechecked all lines for vacume leaks and sprayed with card cleaned to check for vacume problems. I also checked and cleaned the iac the egr and pcv and replaced both front o2's with no avail at all.
Any one got any other ideas to try, I dont want to take it back to the sorry dealership all they will do is swap out more parts and stick it too me.
thanks Mike
Oh yeah I ran some sea foam threw with some ijector cleaner also.

 

Well we have tried everthing thier is to try. Spoke with a shop in Fla. that repairs ECMs and told hem of My problem and He said "Oh Yeah thats a bad capacitor in Your ECM easy fix". Turns out My truck is still under warante, 8years 80k miles, back to the dealer and they work all day on it agian and everthing checked out great. Problem not fixed so they are going to try and replace the computer this week and I will post what We find.
Mike in NC

 

Thank the lord you're still under warranty lol. At least some of the work you are getting done to it will hopefully be under warranty.

The only option that hasn't been covered is the purge valve and solenoid.

 

Post back if this worked.

 

Well to give another update:
The Ford dealership was of no help at all, they have had the truck for 4 days and have tried everthing under the sun and cant fix it and will not try another ECM in the damn thing and the ford rep says well seldom have trouble with the ecms and will not send them one to try. Now they want to put a head on it and Im saying no way, so Im going to go pick it up and send out the ecm to have it looked at My self to AES in Fla. They seem to have a great rep from what Ive read on the web and the customer service teck was first class on the phone. I will post back what I find.
Mike in NC

 

Well this has been a journey for me, turns out that it was an $8 valve spring that was broken the whole time. Where it was at You could not see the break, We just by chance found it. So all in all a eight dollar spring cost a lot more, she runs better now than when I bought it two years ago.
Mike

 

Shake at idle right?

 

It was shaking at idle and most of the way threw the power band, and My millage was half of what I was getting, Also no noise at all, even with the motor runnig and doing a runing copresion check ( not even a clatter).
Hope this helps others by the time we figured it out cost Me close to a grand, Ouch!!!
Mike

 

I ve seen probably 4 or 5 valve springs broken in 4.0s one was a brand new Explorer. Wish I d seen this sooner. Maybe youve helped someone else.

 

It's weird, since I've been on R/F I have seen 2 main problems with the 4.0 SOHCs
1. 01-02 timing chain tensioner issues, that's a given.
2. 04-05 Cylinder 4 and Cylinder 5 compressor problems. I think I've seen almost 5 threads now with the same issues and they all ended up being a valve or head on cylinder 4 or 5. I wonder why that is.

It seems like the only safe year for the 4.0 was 2003 lol. Time to start digging.

 

I ve seen tensioner plastics laying in the pans, and in oil pickup screens in Every year. Spun bearings from oil starvation, bent valves, dropped valves. The 4.0 sohc needs alot of care to last and some luck doesnt hurt. Pretty common to see bent valves on bank 1 after the plastic is in the pan and the chain is to loose. Sad really. The weirdest thing to me is it seems like Explorers have more problems than Rangers.