Minor rough idle, rough shutdown - 163k '03 Civic

Joined
Dec 23, 2020
Messages
355
Location
Midwest
I'm probably nitpicking here, maybe this is just normal for a car this age with this many miles?

Here's the symptoms:
-car idles slightly rough, moreso when cold. By slightly, I mean rpm fluctuates between 650-750. After driven for many miles and warmed up, it sticks closer to 700 rpm. This is by watching idle on my OBD II scanner. And when I say rough, I can feel a slight shaking when it dips closer to 650 rpm.
-sometimes when I shut the engine off after a short drive, the shutdown has a slight delay and sputter (almost like the engine shut down due to running out of gas).

There are zero scan codes. In fact, according to the scanner the engine is in tip-top shape.
The engine never stalls, ever.
99% of the time it starts immediately on the first crank.
1% of the time it will crank as if out of gas, but after shutting ignition off and trying again, starts immediately on next try. This has happened maybe 3 times in the past year, but each time it did happen, it freaked me out because it is so out of character for this car.

Things I've already done in the past 2000 miles:
-changed spark plugs and ignition coils
-tried putting old coils back in, no difference.
-cleaned throttle body, idle air control valve, and MAP sensor
-replaced PCV valve
-replaced O2 sensors

4500 miles ago I had the head gasket replaced. At the same time, they also:
-replaced thermostat and gasket
-replaced camshaft plug and EGR gasket (not the EGR valve itself)
-replaced VVT solenoid gasket (not the solenoid itself)

This is so minor, a typical passenger would never notice. But I've been driving this car daily for 18 years, so I notice it. Maybe this is just a new normal for a car this age...LOL
 
Joined
Jun 12, 2004
Messages
2,073
Location
Athens, GA
I might be blind, I didn't see how many miles on the engine, but. If you're to the point of doing all that other maintenance, you're probably due to adjust the valves.
 
Joined
Aug 10, 2017
Messages
266
Location
Iowa
It idles worse when cold. Maybe some carbon on the intake valves? Run a couple bottles of Techron or some BG44k in the gas.
 

himemsys

Thread starter
Joined
Dec 23, 2020
Messages
355
Location
Midwest
I might be blind, I didn't see how many miles on the engine, but. If you're to the point of doing all that other maintenance, you're probably due to adjust the valves.
163k. It's hiding in the post title. :)

Valves were adjusted when they did the head gasket at 158k. Maybe they didn't do it right.

It idles worse when cold. Maybe some carbon on the intake valves? Run a couple bottles of Techron or some BG44k in the gas.
I run a bottle of Techron twice a year. Ran a bottle through at 158k and 160k.

I'll start researching vacuum leaks and valve adjustment. Thanks for the tips!
 

himemsys

Thread starter
Joined
Dec 23, 2020
Messages
355
Location
Midwest
I was thinking fuel rated to
Speaking of fuel related, last February when we had that brutal cold front and several days of negative temps, my car would not start on a couple of of the coldest mornings. Once we got back to normal cold (30-40F in the winter), it had no problem starting.
 
Top