causes for low idle (gasket, brake, mileage, engine)

[kapikap]

i recently purged the air from my radiator, and changed the radiator cap on my car. I was getting overfill in the coolant overflow container. now, I have low idle and vibration when cars is stopped in gear. everything else is smooth as usual when driving, accelerating, etc.

what can be the cause? no check engine light, but I do get a maintenance light.

[kwong7]

Make, model, year, engine, trim, mileage?

[kapikap]

acura rl 04 over 200k miles

[M3 Mitch]

Not enough information to make a conclusive diagnosis, but, if you have a full "puke" can with "air" in you radiator, one way that can happen is to have a leaking head gasket (or cracked head, or even block).

Not to be all doom and gloom, but. You can get a simple kit to sample your coolant, check for combustion gases.

If this car has an aluminum head(s) and iron block, that setup, while generally excellent, does have a limited life for the head gasket due to differential expansion of head and block. 200K is a lot for a head gasket in that case. I don't know that this car has this set up though.

[kapikap]

I will check with a coolant test, thanks.

The car runs smooth, no vibration in drive, all the way to 85 mph. Smooth driving all speeds. Tempeture stays the same for hours.

Recently had oil change, brake pads and rotors replaced, ac issue figured out. Maintanance is up to date.

Antifreeze looks clean, pure color. I bleed the coolant system of air, no bubbles, no repeat in overflow can. Change the rad cap for good measure.

I even reset the computer via battery unplug. No codes in past 250 miles. No smoke, leaks. Rough idle went away for a day, but still there.

What would cause the idle to lower, and cause the shuttering/vibration? Its mild now, but was smooth before.

[sunsprit]

with all that recent underhood work, you may find that a vacuum hose or an electrical connection has been disturbed ...

leading to false air entering the intake manifold or a sensor not getting accurate information to the computer.

time now to take a good look underhood and check for those possibilities.