1989 F250 460 runs great, horrible idle
 

i have an 89 f250 with a 460 with only 50,000 miles. it runs great on the road and will pass anyone going down the highway with ease and if your not careful it will smoke the tires in a heartbeat, but when it idles it spits and sputters missfireing so bad the entire truck is shaking and raddeling and if its in drive or reverse it will usually die out at red lights. when it warms up it gets a little better but still not great. it also hesitates when you hit the gas but the timing is right i checked it with a light. its not running rich eather because i just passed emmissions just yesterday. it got a score of 34 ppm of HC on the high rev test and a 184 ppm HC on the idle test.(dont know if those numbers help at all just thought i would throw them in there) it did sit in a field for 2 years but the tanks are clean and i just replaced the fuel filter. there is no check engine light after i replaced the ACT sensor, EGR Pos. Sensor, and the vaccumme regulator for the EGR valve. Anyone have any ideas?

P.S. sorry for the bad spelling, its so bad that spell check does not known what word i mean.

the place to start is to check for codes. do a search on here its easy to do, but read the directions and follow them carefully. you gotta do all kinds of things like turn the wheel and do a wide open throttle, ect.

I would start with 4 flat tires' advice as a starting point. But, until you can pass the KOEO tests and see what is in Continuous Memory (CM) there is no reason to go into the KOER tests they were referring to.

The next question to you is when was the last time the truck had a tuneup with fresh/new plugs/wires/cap/rotor and filters? Never ignore the obvious, start with the simple things first.

Does it have and Idle Air Control Valve?

yes and i pulled off teh servo thing that moves it and tried to push the valve with my finger while it was idleing trying to find if there was a sweet spot but there wasnt it would idle it up but still rough.

codes are only one sence i replaced the sensors. and the code is 11 which according to the internet means all systems pass and it gives that code in running (where you turn the wheel and rev the engine ect.) mode or off mode.

tuned it up just the other day, new plugs, wires, cap, rotor, cleaned the air filter(it has a K&N box filter), new fuel filter, and ran Seafoam in the gas and in the intake.

bump............

Are you saying it still runs bad even after tune-up?

They only things that come to mind are fuel pressure, spark plug wire routing and perhaps a compression check. What about the timing, how did you check it? SPOUT out, what was the base timing reading?

check for vacuum leaks as well. if you got one of those metal cans, i would start with that. mine had pin holes around the seam on top.

Here is an update, truck still runs exactly the same and still no check engine light but i decieded to run the codes anyways. when it is off it says code 11 all system pass but when it is running it says code 18 SPOUT Circuit open or spark angle word failure my book also says code 18 can mean IDM circuit failure or SPOUT circuit grounded. anyone have any idea what this code means? It only appears when in running test mode.

Replace the IAC. REPLACE IT-do not try to clean it. Could be a vacuum leak as well. When I bought mine, the hose leading to the PCV was rotted off. I had this same problem on my 460. The guys on here are very helpful though-know their stuff! That IAC getting replaced on mine made all the difference. Hope it helps.

try running without the spout, it should at least idle.. did you do this when you set the timing? did it idle decent then? also check the wires out for it, maybe switch one from another truck with the same motor if you can. i have no idea of what the code means, i'm just throwing stuff out there.

i did pull it and it is coated in a thin film of carbon but it apears to work. Should i replace it anyways?