Low gas mileage/high idle and low power for cold engine

[suraj]

My 99 Honda Civic LX has 140,000 miles.

A few months ago, I noticed the engine rpm when the engine is cold or cool (when started up in the morning) shoots to 1500 rpm. Once, engine is hot it reduces to 700-800 rpm which I think is normal rpm.

I also lost 5 miles per gallon at the same time. Are the two things related and what could be causing it?

Also, when the engine is cold I dont have much power but once warmed up i have the power.

So, I want to know how to resolve low mileage and high cold engine rpm.

Thanks for your advise.

S

 

[RonJ]

A few months ago, I noticed the engine rpm when the engine is cold or cool (when started up in the morning) shoots to 1500 rpm. Once, engine is hot it reduces to 700-800 rpm which I think is normal rpm.

^This is normal.
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How old are the plugs, wires, cap, and rotor?

Have you checked the ignition timing with a timing gun?

Any CEL codes?

 

[suraj]

Plugs are preety old (i guess never changed since bought brand new).

No CEL codes.

Did not check ignition timing.

What is the rotor in your first line?

 

[RonJ]

Best bet would be to replace all of the ignition components that I listed.