99 4.0L running bad and will not go over 50mph...

[joedawg]

Long story short, kid came home from college and the truck was running real bad... 99 Ranger 4.0L 4x4 137000 miles.... Missing, hesitating, and would not go over 50mph... Ran the codes, misfire on cyl 3 and 4... put in new plugs, cleaned map and IAC... ran a tad better but codes still show misfire on cyl 3 and 4... replaced the plug wires... runs about the same, real bad and will not go fast... put in a new coil... still running bad and will not go over 50.... same codes... replaced injectors on cyl 3 and 4... runs a tad better.. not the best idle but better... not throwing any codes but only drove it for 4-5 miles... driving the truck is like you are pulling a huge anchor... you put the gas pedal to the floor and the truck gradually picks up speed... does not want to shift though.. if you lift your foot a little, then it shifts... and eventually you top out at 48-49 mph... any help in diagnosing this will be greatly appreciated..

 

[Lift]

Did you reset cyl 3 - 4 and do a firing/ injector test on it? Is your timing on? also get new Spark plug wires and get a new cap and rotter those go bad after a while.

 

[Sasquatch_Ryda]

I bet the missfires cause a bunch of fuel to be dumped into the cats, causing them to melt down and plug up restricting your exhaust.

 

[TrexMex]

^^+1...

Check for restriction in the air box/MAF/air duct/throttle body assembly, and disassemble the exhaust assembly to check for plugged cats. IF making a helluva noise is no problem in your neighborhood, try running the truck with the exhaust pipes disconnected from the truck to see if that makes a difference. Generic cats you can get for as low as 100 bucks in the event yours are plugged. OEM ones, whole different story; either or, gotta put them back in! it's the law

 

[camper4lyfe]

I had an old Volkswagen GTI that did that. Had no power and wouldn't go over 45mph. It ended up being plugged injectors.

 

[myranger26105]

my 03 was doing that and it turned out to be all the cats had melted and clogged up mine cost almost 1100 to fix