# Rough Idle



## joecaption (Nov 30, 2011)

F150, 4.6 2002, 60000 miles, runs fine up to speed, starts right up, service engine soon light come on and will stall at idle, new air filter.
I've called three local garages and they can not work on it for at least a week.
I bought a new fuel filter and will install it this weekend.
Any ideas?


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## Gregsoldtruck79 (Dec 21, 2017)

I wonder if your truck has the OBD 2 and maybe you could stop by Advance Auto or AZ and let them read the CE code for you ?


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## lenaitch (Feb 10, 2014)

Gregsoldtruck79 said:


> I wonder if your truck has the OBD 2 and maybe you could stop by Advance Auto or AZ and let them read the CE code for you ?



That would be my first step. I don't know what was installed in 2002 but if it has a check engine light there must be some manner of diagnostics. Mass airflow sensor perhaps?


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## de-nagorg (Feb 23, 2014)

Yes check that air door controller and mechanism.

Ford was notorious for failures of it, the controller senses that the outside temperature is cold, but it is not cold enough to need a restricted air flow, but it restricts it anyway, and you get rough idle, and often stalling. 

In the fall, this happens a lot, and needs technical work, but any one with a bit of brains can repair the thing.


ED


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## Bigplanz (Apr 10, 2009)

New fuel filter is a good move, particularly if it has never been changed. It is not related to the problem though. Pull the codes, I am going to guess IAC or EGR related.


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## SeniorSitizen (Sep 10, 2012)

Using a IR determine which cylinder(s) is not firing.


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## Brainbucket (Mar 30, 2015)

Check for vacuum leaks. 4.6 was bad about the pcv hose leaking. Follow it as it is connected to plastic hose the goes to rubber in 3 places. The "T" in that hose is usually the one leaking. Check for air leaks in the air intake hose from MAS air flow to throttle body. Check fuel pressure.:vs_cool:


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## ChuckF. (Aug 25, 2013)

Get the codes read before you do anything else.


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## joecaption (Nov 30, 2011)

I found out what was wrong.
I tried to make an appointment at 3 different dealers and all said it would be 2 week before I could take it in.
I had heard about a small local garage that was good on Ford trucks so I stopped in to see when they could work on it.
They took it right in to at least run the codes.
One of the older guys there heard how it was running and says, yup you have a vacuum leak most likely it's this hose, and he points to about a 3/4" hose that runs from the rocker arm cover to the back of the engine someplace.
He runs his hand over the hose near the back and when he hits the place it was bad the engine stops acting up.
It was a plastic elbow on the end of the hose that was bad.
The NAPA was right across the street and they had the part, in fact they had a box full of them!
I was in and out in about 1/2 hour.


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## Bigplanz (Apr 10, 2009)

joecaption said:


> I found out what was wrong.
> I tried to make an appointment at 3 different dealers and all said it would be 2 week before I could take it in.
> I had heard about a small local garage that was good on Ford trucks so I stopped in to see when they could work on it.
> They took it right in to at least run the codes.
> ...


Same problem I had with my Navigator last November. Pictures!


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## de-nagorg (Feb 23, 2014)

quotation: The NAPA was right across the street and they had the part, in fact they had a box full of them!
I was in and out in about 1/2 hour. 



And you paid a lot less than the dealers price too.

N A P A part, and the shop price was probably half the Dealer price.


ED


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## SeniorSitizen (Sep 10, 2012)

Hey, cut the dealers a little slack.:biggrin2:They are back logged installing parts that don't need replacing. That's where the money is.


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## papereater (Sep 16, 2016)

Joecaprtion is sooo lucky- I wish I had a vac leak which I could find in a day or so. Mine- been chasing it for oh, about 16 years now. Never found it. I have tried ALL the methods out there- many times. So difficult to find. Sheesh. 

Meanwhile, I keep driving the car.


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## SeniorSitizen (Sep 10, 2012)

i've experienced vacuum leaks on 2 vehicles, 65 ford and a 70 chevy. ford leak where a intake manifold gasket should have been. factory manufactured without a intake gasket. ford leak kills #3 cylinder at idle. found leak with an eye dropper of gasoline. 



bend in hose leak on chevy simultaneously kills 2 cylinders at idle. found leak when it sucked a hickey on my finger.


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## papereater (Sep 16, 2016)

SeniorSitizen said:


> i've experienced vacuum leaks on 2 vehicles, 65 ford and a 70 chevy. ford leak where a intake manifold gasket should have been. factory manufactured without a intake gasket. ford leak kills #3 cylinder at idle. found leak with an eye dropper of gasoline.
> 
> 
> 
> bend in hose leak on chevy simultaneously kills 2 cylinders at idle. found leak when it sucked a hickey on my finger.


Thanks, but youre talking about ancient cars- had lots of room to get one's hand/fingers around. No way I can get a dropper with gas in the back bottom of my intake. Top maybe yes, but not bottom/back. But I already did the "stethescope" test- vinyl tubing, 3' long, 1/4" ID, one end on ear and other end scoping around suspect areas. You will immediately hear the leak as a whoooooooshhhhhhhhhh. Found one this way. Hearing is believing. 

But this one- cant hear anything anywhere. 

Anyway, I do appreciate your advice and feedback.


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## w0j0 (Dec 29, 2017)

lenaitch said:


> That would be my first step. I don't know what was installed in 2002 but if it has a check engine light there must be some manner of diagnostics. Mass airflow sensor perhaps?





Gregsoldtruck79 said:


> I wonder if your truck has the OBD 2 and maybe you could stop by Advance Auto or AZ and let them read the CE code for you ?


Just for future information-- 1996 was the first year for obdii ports. Additionally, many vehicles, prior to obdii, had their own proprietary diagnostic methods. Ford had a port that you'd install a jumper wire into and it would output codes in flashing lights; vw had, and still has, the most comprehensive diagnostics of any car I've had the (mis)pleasure of working on, with a computer that interfaced with the car's computer and could test the systems and individual sensors throughout every sub system of the vehicle, ie brakes, transmission, interior lights, etc

To the OP, glad you got the issue resolved; it's always nice when things work out to be simple, inexpensive, and quick


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