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1990 bronco II poss fuel system problem

mandrake001x

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1990
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Its been running fine other than idling a little high (2.9 liter EFI 5 speed stick - about 1200/1400 in neutral or with clutch depressed). Starts easily when cold, but when warm is a little harder to start and seems to 'miss' a little at first, then smooths out. Today after driving about 40 miles, engine began to sputter and buck and seemed to run smoother with the clutch depressed (out of gear) but actually stalled out and died at one point, almost like it wasn't getting fuel. Let it sit for a couple of mins., and it started up and seemed to run fine, with only an occasional buck. I'm thinking its a dirty fuel filter as letting it sit for a couple and it runs ok. If the info I have is correct, the fuel filter is on the frame rail, drivers side and requires a 'special' tool to change it. Probably original equipment as the previous owner didn't seem to know what preventative maint. meant. Any suggestions as to what else might be causing this if its not the filter. Will install a new one once it warms up some. Tks...
 
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RonD

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Yes, for $10 I would change the fuel filter, some just have the clips which can be removed with a screwdriver, some fuel filters come with plastic tool to remove lines.

Usual sign of a clogging fuel filter is a loss of power when trying to maintain highway speed.

When engine is cold is the idle higher?
Or does it just stay at 1,200rpms even after it warms up?

On fuel injected engines an "idle screw" will not work, the idle must be computer controlled by using an IAC(idle air control) valve.
The IAC Valve is on the upper intake manifold near the throttle, it is an electric motor that is used to open and close an air passage that runs from one side of the throttle plate to the other, so in essence the IAC valve is a "controlled" vacuum leak.

IAC valve is easy to clean, just two bolts to remove it.
If IAC valve is sticking open then idle will never drop down to 750rpm warm idle.

A vacuum leak from PCV hose or PCV valve can also hold idle high, computer closes IAC valve to lower idle but there is too much "other air" coming in.

With IAC valve removed you can block the holes, so no air gets passed throttle plate then start engine, if idle stays low then IAC vale is the issue, if idle is still high look for vacuum leak, but still clean the IAC valve.
 
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mandrake001x

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Tks Ron.... will check out the other two items after I replace the fuel filter. :icon_thumby:
 

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