Weird/low idle

[freelove33]

I just bought a 2000 civic lx with the 5 speed. Car is pretty clean and has 145K on it. It's in pretty decent shape for it's age. I just picked it up last week and have recently noticed a couple things. Number one, and most importantly is that it seems to have a bit of a weird idle/run slightly off. It's mostly noticeable when I'm idling. The RPMs drop and starts to run a little rough.

Starts fine and shows no check engine light, and yes the bulb is fine. The light comes in when you first turn the key. I thought it could just be a misfire but I assume it would throw a code for that. I don't have a scanner to check. Any ideas?

My other issue is my temperature gauge is off and sometimes bounces around.
Cold/off:

Warm:

I'm not as much worried about my gauge since it's seems to be below where it should be cold the same amount as when it would be warm. The engine also gives off no sign that it could be overheating. I appreciate any and all input!


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[freelove33]

How long should it take these motors to warm up? It says to run it until the fan comes on twice but my fan hasn't come on. It does work since I've checked it right after I've driven it but I haven't seen it come on just idling


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[freelove33]

Car probably ran for 45-60 minutes. Fan never came on.


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[freelove33]

I downloaded the manual, but I only topped off the overflow. I didn't remove it and clean it. And I didn't need to change the coolant. From there all I did was take the cap off, radiator was full, and put it loosely back on. Started the car, turned the heat to max, and the blower to max and let it idle. The engine did not over heat, don't think it even got close. The original issue is still there, though the idle issue may have gotten a little better. As in when the idle does drop, it doesn't drop as low or as much.


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[freelove33]

It might have dropped a little. Not a significant drop in the level, but enough of a difference to make me question that it did drop. There were also no leaks that I found.

I can't say for certain that I saw bubbles in the radiator. I thought I did but it could have been the vibration in the fluid coming from the radiator.

The needle stays in the same place as it is in my pictures. I haven't driven it much so I can't speak for the slight bouncing of the needle. I will watch it closely over the next day.

The Civic is stock except for small items such as a timing belt, head unit, and a viper alarm system.


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[freelove33]

The temp gauge still has a slight fluctuation, though when it gets fully warmed up, it doesn't move.

The idle doesn't seem to drop as low, but it still surges a little bit. Obviously it changes when the other fan(for what?) flicks on and off. It has never died on me. Sometimes while I'm driving at a constant speed/RPM, I can feel the surge, so I'm guessing it's more than just an at idle thing? Unless that is caused by the second fan coming in and turning off


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[dchobo]

Did you reconnect the battery recently?

My 97 Civic sometimes would have low idle if I disconnect and reconnect the battery. But OK after a few days.

I think autozone has free OBD scanner your can borrow?

 

[freelove33]

I will have to keep trying to get a video. Hard to do while driving. I am guessing I just need to do a better bleed. I don't see how it would start and run so well with a blow head gasket. I also don't see any mixture of coolant or oil.

I have not disconnected my battery at all. This has been going on since I got it almost 3 weeks ago, so if it was my battery, it should have cleared like yours did. I have scanned for codes and there are none.


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[JohnS.]

If you have a blown headgasket, you'll know pretty quickly. Signs to look for: white smoke coming out the exhaust (or smelling coolant coming out the exhaust), bubbles in the radiator cap or overflow tank, milky oil, losing A LOT of coolant with little to no leakage. That last one is the one that did it for me. I'd fill my radiator, burp the system, and in about 5 days, my car would overheat.

Your temp gauge is where it should be when warmed up. At least that's how my needle was when my car was warmed up.

I've read it also helps to have your front end raised up when you burp the system. Helps eliminate air in the system. Also, turn your air on full blast, high heat. You can rev your engine to 3k too if you didn't before. It'll warm up faster. And like others have said, wait for the radiator fan to come on a few times.

 

[Brak]

My car started doing the same thing (idle), after the front O2 sensor was disconnected, but only after it's been operated for a while. like when stopping at a red light.
when i replaced the damaged header, the sensor was too mangled to swap over. I haven't gotten around to replacing it.