rough idle

[rogmit]

my truck is still idling rough,i've taken suggestions,replaced cap, rotor wires, i changed the tps and i cleaned the idle air control valve but it still is idling rough, it didn't start until a ignition coil went out, it couldn't be in the timing chain or valves could it because it still has good pick-up it just idles like ***** i even replaced a few vacuum lines that i thought my be bad-----does anyone have any ideas what i might be overlooking or is it time to haul it into a shop? :angry:

 

[ocalabronco]

sounds like a vaccum leak elsewhere other than lines, or a bad FPR

 

[Broncoholics]

Might want to do a compression test, this will tell you if you have a broken valve springs, bent valves, cracked pistons or bad rings.

Do an air leak down test to see if the valves are leaking. This was my low rough idle problem. On mine, the valves were recessed up inside the head by 1/4" and leaking due to the change from leaded gas the unleaded. You need to upgrade to hardened valve seats. After I had them fixed up the truck ran like a million bucks.

 

[TX_BEAST]

may also be mass airflow sensor. ive heard of them making idling problems and will also degrade fuel mileage.

if anyone asks just tell them its all cam.