stumbling idle and stalling
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New User
Joined: Aug 2002
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stumbling idle and stalling
hey all. i have an 87 2wd with the inline 4.9. after starting it, it will idle high like it usually does then when the idle goes lower, it starts to idle crappy, and you can hardly put any throttle input into it or else it will stall, you have to play with the throttle for a few minutes to get it to the point where it wont stall. but once you have driven it for a while and it has gotten warmed up it doesnt do it as bad. it wont stall but still idles like crap in gear or in neutral or park. it also smells like unburned gas until it warms up. any help would be grately appreciated. i'm am thinking it needs a tune up. what do you all think?
Senior User
Joined: Dec 2001
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stumbling idle and stalling
I can't remember if that's the 1st year of EFI or its a carburated motor. If its carburated, a problem with the choke would be my 1st suspicion. Either way, I know its a computerized motor, so run the codes. I'm thinking EGR sensor, or MAP.
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Joined: Sep 2002
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From: Meggett USA
stumbling idle and stalling
I had the same problem with my 84 F-150 300 6 it turned out to be the EGR valve the valve appeared to operate properly but upon internal inspection the valve disk was half gone causing a massive vacuum leak. The vacuum leak caused the engine to stall.
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From: Sullivan, IN
stumbling idle and stalling
I have a 89 F-150 4.9 l6 Last week I did an oil change and pulled a ground wire off and forgot to hook it back up. Well I drove 20 miles to work and at 15 miles the service engine light came on for 2 days it did this then I remembered to hook it up and all this time it ran fine (when the service engine light was on) So I fixed that and the light never came on again. A few days later I was going to clear the codes and disconnected the battery and now that thing will NOT idle till it gets warmed up. Plus it sucks the gas bad during the warm up. I have pulled and checked. IAC, O2, TPS, coolent sensores and all have tested within spec of a haynes book. The codes I have gotten are 52-power steering switch open (it has no switch) 67-AXOD Transmission in neutral (it has a 4 speed manual) and 111-system pass. Any ideas to this problem would be great. 
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Joined: Sep 2002
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From: Sullivan, IN
stumbling idle and stalling
I also checked and cleaned egr valve today. I checked the fuel pressure regulator and everything is in specs. I also went ahead and changed the fuel filter even though it's only a month old still not ideling till it warms up. I think the problem may be the IAC has not been reset after disconnecting the battery I mean it all started when I disconnected the battery to clear the codes. I have looked all over to try to find how to reset the IAC and not came up with anything.
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Freshman User
Joined: Sep 2002
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From: Sullivan, IN
stumbling idle and stalling
Just an update. I called my local Ford dealership and they told me how to reset the IAC. For those who don't know. 89 F-150 300/6 drive 5 miles with the ac on then drive 5 miles with ac off then shut it off wait 5 min and start it. But anyway I had a hair up my butt to just turn the manual base idle up a bit upon doing that I found that it had backed itself out so thats where the lobbing came from it idles at 850 rpm really steady but there is a small miss and I think that may be from changing to autolite platinum plugs so I'm gonna go back to standard autolite plugs and see what happens. I'll keep up to date on what happens.
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Freshman User
Joined: Sep 2002
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From: Sullivan, IN
stumbling idle and stalling
I put new plugs and a fuel filter in it and still didn't clean up the idle. I started unpluging things and when I unplugged the MAP Sensor that thing purred like a kitten and never missed a lick. So I believe that a MAP sensor might just do the trick. I'll pick one up tomorrow and I think thats gonna fix it.
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From: Sullivan, IN
stumbling idle and stalling
Pop the hood and look to the left, the heater hoses go into a black box on the left right next to the hood hinge. the MAP sensor sits right on top of the heater hoses it has one vaccum line and one 3 wire connector goin to it. Unplug the electrical connector and see how it runs. Mine ran like a top after I unplugged it, but don't unplug the vaccum line or it will die. So for now I left the electrical wires unplugged and it's runnin great, but the engine light will stay on. But it runs fine.
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From: Sullivan, IN
stumbling idle and stalling
Update. Idle problem fixed and it is runnin like a top. Idles steady at 850 RPM. Thank you all for your help it was just a matter of checkin things out. I used a Haynes manuel for all of the testing and a voltmeter and some patience.
