I have a 93 f150 4x4 with 5.0. When i start the truck up it idles like normal. After it idles down, It just begins to idle high and low. It also does it when i stop at street lights and stuff. I believe its the idle posistion but idk some help would be nice. thanks

 

welcome to the rough idle club!everyone is going to tell you the same thing..starting with checking for codes!then vaccum leaks.followed by injectors being clogged.fuel filter need to be replaced.check fuel pressure.blah blah the list goes on...and none of them fix the problem...so join the rest of us with this problem and no solution!

 

o yeh ive replaced in mine since having the same problem...

spark plugs
spark plug wires
cap/rotor
ignition coil
egr valve
egr tube
evp sensor
vaccum lines
numerous injector and fuel cleaner
seafoam
throttle body cleaner

and still same problem!

 

I had same problem..I did a tune..no help..Seafoamed..little improvment..I then got voltmeter out checked voltages all sensors..TPS came back voltage HIGH..Replaced TPS and IAC valve. All is good now Truck idles like a dream.Check the codes..and if related to a specific sensor..change it. I changed the IAC Valve cause I already had bought it. I took the EGR Valve back unopened and got $$ back..I didnt have the IAC Valve in unopened box (tossed it out).

I say Check the codes first then Seafoam it good. Check the timing (Base) and then fuel filter and O2 sensor (change these every 30000 miles without fail) and you should be in the Zone!

 

^^^u probaly didnt need to replace the IAC or TPS..they probaly just needed to be cleaned!

 

Yeah I could have cleaned the IAC..like I said..I couldnt return it..and How do you clean a TPS??? Besides Voltage was way out of Limits!!

 

ive done it all just ruins my gas mileage it seems like

 

There were write-ups about throttle body plugs missing causing air leakage. Use search to locate.