rolling idle?
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Freshman User
Joined: Oct 2006
Posts: 48
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rolling idle?
Hey all. I had been having a problem with my 90 f150 4.9 stalling when I was coming to a stop while going down hill.It was suggested to me that I check and clean my IAC and I did and it hasnt stalled in prolly 4 or 5 days now so thanks. But now I am noticing a slight rolling idle when I am in netural coming to a stop, once im not coasting and at a stop it levels out and idles smooth I have been watching and it only happens when im moving.I need advice,could this still be IAC related is not a bad rolling idle mabey 200 rpms so it is not a real problem i just like my ford to run right and she usally does so little things like this bother the hell outta me any advice would be appricated thanks.
Junior User
Joined: Sep 2006
Posts: 57
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Could be IAC still, but may be the throttle body needs a good cleaning. Changed your air filter? PCV valve? I've had those things contribute to rough idle...
Oxygen sensor too...easy cheap change out, and will improve performance if not the idle issue...can cause it to run a little rich...
Oxygen sensor too...easy cheap change out, and will improve performance if not the idle issue...can cause it to run a little rich...
Elder User
Joined: Jun 2006
Posts: 805
Likes: 3
The VSS will keep the engine idling fast, theoretically above 6 MPH. Not real sure about the speed, but that's what I think I read somewhere. Mine seems to drop on my '92 around 14 MPH in 2nd. Very noticeable drop. If the VSS signal is a little wonky, it may be confusing the EEC about where the idle should be. I got 130K outta the factory pads on the front, and still going at 145K on the rear shoes, so needless to say, I stop with the engine a lot more than I do with the brakes. Mine's always been a little early on dropping the idle, but it's never bothered me at all. But, I can't remember it ever oscillating while coasting down in neutral, or ever noticing any oscillation while engine braking. If I remember what I read right, the VSS is used to set the IAC and timing so that the engine provides better braking. I don't know that there's any difference in the setup between the autos and the 5 speeds, but it would certainly be more noticable with a manual tranny. The VSS is use for the RABS or ABS, speedo, idle check, cruise, lotsa things. Notice any other weird things happening?
