I have 96 f250 5.8 and lately its started to idle really rough. when i first start it in the morning its fine, then it starts to get rough. every now and then it will even out for a few seconds then get rough again. Also when i put it in drive it bogs way down and sounds like its going to die, then springs back and the truck tries to lurch forward. Any ideas? I'v done a basic tune-up (plugs,wires,coil,cap,rotor,fuel pressure regulator) Thanks

 

Sounds like you may have a vaccum leak. Is it throwing any codes?

Also as for the tune-up, don't forget the fuel filter and PCV valve, it also wouldnt hurt to clean out the throttle body. I am not sure if the F250/350's have MAF senors, but if they do, make sure the senor itself is clean too...

 

forgot the mention i have changed the fuel filter, pcv valve though i have not. would that cause this?

 

Clean the IAC valve

 

catholic converter i had this problem with my 87 ford half ton 351 carb. I know your is Fuel injection just trying to help. Hope you get it right .

 

What all do you have to do to clean the IAC sensor? and where is it? I dont want to mess anything up, daily driver. And cats aren't my problem because i lost those a long time ago

 

Sounds like a fuel pressure problem to me, put a gauge on it ans make sure it's making 40psi all the time.

 

I had a gauge on it last weekend, if i remember right I had about 37 at an idle, 40 with the FPR (new) hose off. But the odd thing was when the truck was off and the pressure had relieved, if i cycled the key i only gain about 2 psi per cycle, but it started fine. I was checking it to see if I had a sticking injector, but im not sure how fast the pressure should bleed out. is this normal for the pressure? thanks

 

Anybody? I want it to run nice and smooth again

 

I had a 95 f150 with the 4.9 straight 6. Had the same type of issue. I replaced the entire fuel system, the entire ignition system, oxygen sensors, crank sensor, coolant temp sensor, idle air control valve, and still couldn’t figure out why it wouldn’t run. I didn’t want to waste any more money on parts so I finally swallowed my pride and took it to a shop. They replaced the MAP sensor and it ran fine for about three months and started running rough again. Ended up being the Engine Control Unit. Ran great after that.