I am having an issue where the idle goes from like 800 to 1500 rpm back and forth after the car has warmed up and is idling in park. I believe this is the coolant system, but I can't get the bubbles out. I have filled the radiator, and then run it with the bleed nipple loosened. The car burps out coolant and then nothing, burps, then nothing. I tried this for a while, to no avail. I just can't get it to run out steady. I have tried it with and without the radiator cap, and I have tried it on a very slight incline as well (the rear of the car lower a couple of inches) Any help with this would be greatly appreciated.

 

What year accord do you have?

 

1994 with an Automatic transmission.

 

You aren't supposed to run the car with the nipple loosened.

Jack the front of the car up.
Open bleeder valve.
Fill radiator w/ coolant until a steady stream flows out of the bleeder valve.
Fill reserve tank to appropriate line.
Close bleeder valve.
Start car w/ radiator cap off + turn heat on high.
When coolant begins to flow out, put radiator cap back on.

 

Drain the coolant out, open the bleeder bolt, then pour the coolant back in, until a steady stream of coolant comes out. Then close the bleeder bolt. It works much better that way.

 

Thanks for your help. It bled great this time, without the engine on. Thankfully it was just something dumb that I was doing.

However, the problem continues, It idles high then low....... I think the gas mileage has also gone down since this problem has started. Any ideas on how to diagnose it? I have looked for obvious air leaks and haven't found any.

 

Are there any stored codes in the computer? If the input temp sensor for the computer is bad, has air in the cooling system or the thermostat doesn’t open you will get the rapid surging. This is usually after the cooling system has been worked on. The sensor needs a good flow of the coolant to work correctly. Pretty much anyway you bleed the system will get air out if the thermostat opens and you bleed it after that. You problem may have nothing to do with the cooling system.

 

Your EGR ports may be clogged (common) or your idle control valve may be plugged.

 

are you sure your thermostat is still opperating correctly? but like he said before it may not lie in the cooling system at all.