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99 towncar rough idle

Within the past few days my towncar has developed a rough idle. When I’m stopped at a light or stop sign it jumps and just plain idles rough. This also happens when I change speeds after either accelerate or decelerate. I travel an average of 80 miles a day total to and from work and my car has about 140,000 miles on it.
Any help would be greatly appreciated.

Check engine light on? Compression in each cylinder? Spark plugs and wires? RPM at idle?

“Within the past few days my towncar has developed a rough idle”

What has the weather been like where you live? 

Have you kept up on maintenance (like fuel filter, air filter etc?  What part of the world (country) do you live in?

I’m in Louisiana. And the weather has been a bit chilly. But it was much colder last week than it is now. And yes I have kept up on maintenance. I just had a new fuel filter, and fuel pump put in as well as had an oil change and air filter replaced and things of that nature.

And yes my engine light is on.

Have the fault codes downloaded and post them here. Many parts stores will do this free of charge

If I had to take a wild guess, I would guess the vacuum tee on the back side of the plenum has deteriorated and is leaking. This is common after over a decade of use and can be tricky to find if you don’t know where to look. Replacement is cheap and easy if this proves to be the problem.

Went and got my engine light read yesterday. I have two misfiring spark plugs. Now whether its just the plugs or the plugs and the coils is yet to be seen.

I have two misfiring spark plugs. Now whether its just the plugs or the plugs and the coils is yet to be seen.

Good to see you are now on the right path towards finding the real problem.

So I got a full tune up. I got all 8 spark plugs and one coil replaced… Afterwards I found out that I have a small leak in my intake manifold. What fun.

What kind of leak? Coolant or air? Replacing the manifold is a fairly common but tricky repair…Shop around and get several repair estimates…

Coolant leak. And yeah I know it’s fairly common with the manifolds being made of plastic and what not, but it’s just one thing after another.

Too bad you didn’t have the intake manifold replaced for free during the Ford recall period for this problem.

Aww that would have been wonderful. I didn’t take ownership of this car until 2009. When did they do that recall?