97 Expedition idle rough and low RPM's



I have a 97 Expedition and I have noticed lately that at stop lights the engine starts to idle really rough, almost like the car is potentially gonna stall. It also seems to be idling at a low RPM somewhere around 6,000 and it used to be about 9,000. Any help or advise would be great.



Tell us the maintenance history as far as filters, plugs, plug wires, oil changes and mileage please. Any other symptoms such as it only sounds bad when I hit the brakes etc.


I am the second owner of this car. It was regularly maintained by the previous owner. It currently has 121,000. I have not replaced any filters or plugs since owning it and dont know if they were replaced or when they might have been. The only symptom is when the car is at a stop light with the brake down when the car begins to idle rough. It feels like the engine is shacking and could potentially stall. I usually give it a little gas and sometimes will put the car into nuetral and give it a little gas. But it still will idle rough after that. HOpe that gives a little more insight to the problem.



The problem with just saying “regularly maintained” (whether your judgment or that of the previous owner) is that this means different things to different people. Some people think that regular oil changes and car washes means “regularly maintained.”

So the short story is that if you don’t know anything about history of things like spark plugs, wires, fuel and air filters then you should just deal with those things first. Plugs & wires can be inspected for age/condition as can air filters. The fuel filter should just be replaced.

Just FYI - since you don’t seem to have specific knowledge this car is also due for its 4th transmission service (new filter every 30K) and the cooling system probably needs attention too.

Many of these issues are just from neglected items - like old plugs or filters.

Is the check engine light on?


engine light is not on.


I assume that you mean 600 RPM instead of 900 RPM (not 6000 & 9000). The first suspect should be the IAC (Ford calls it Idle Air Bypass Valve). When they get dirty, they start to stick, and can cause your symptoms. They are easy to change and cost about $80.


Thanks tardis, i will look into that.


Start with the basics. Plugs air and gas filter are a good place to start, in addition to cigrollers comments.