1987 Civic CRX slow to warm up

My 1987 (carbureted/automatic) CRX idles at about 1600-2000 rpm at startup and throttles down to about 800 rpm after it’s warmed up. The problem is that it takes anywhere from 2 minutes to 5 minutes, depending on the outdoor temperature, to throttle down when I initially start the car. “Blipping” the gas pedal doesn’t help. Is it normal for this year CRX/Civic to take so long to drop off fast idle ? If not … any ideas how to diagnose and fix it ? Other than this problem the car is a real gem and runs perfectly.


Frank in Arizona

My '89 Accord is carb’d and does the same thing, warms up slowly at about 1600-2000 for about 3 minutes then drops down to about 750. No big deal . . it has done this since I bought it new. If it bothers you, turn on the lights, A/C and rear defroster after you start it up . . this will bring it down to about 1000. I think that it is normal and just drive it 'till it has warmed up. Rocketman

Replace the thermostat if it’s more than 4 years old.

Being an A/T doesn’t it drop down when you put it in DRIVE ? My 5 speed will drop down to whatever speed the gear will use once in gear. Rocketman

Yes … It will drop down somewhat by putting it in drive … however … dropping it in drive at 1600+rpm is rather jarring, even with the brake held down firmly. Once it’s warmed up and idling at 800 rpm. this is not an issue.

OK. Makes sense. Might there be a chance that the thermostat IS working as it should and some sensor or other isn’t reading the temp correctly ? I wonder … just how fast SHOULD this motor reach operating temps when it’s 75 or so outside ? Any idea ?

At 75, the idle should start creeping down in about a minute or two. It sounds like everything else is working but it’s just taking the car a while to warm up-- a thermostat would be by far the simplest explaination. Does this car have a temp gauge?

This car doesn’t have a temp sensor in the modern sense of the word, but rather a couple of thermovalves that sense the coolant temperature and allow vacuum to reach the fast idle unloader. Here a picture:


Yes, the car has a temp gauge.

Thanks for the gif/diagram.
FWIW, unlike the diagram, I believe my car has an electrically operated choke opener.

I’m not averse to replacing the thermostat, which I’ve done on my wife’s '89 CRX Si (5 speed/fuel injected), but … I wonder … are there any tests I could do to confirm that the thermostat IS the problem or is this just a situation where I replace parts until the problem is solved ?

“are there any tests…?”

Yeah, remove the thermostat and put it in a pan of hot water.

How old is the thermostat?

If it’s more than 4 years old it should be changed anyway as a matter of maintenance.

I removed the thermostat and put it in a pot of water on the stove.
It opened at around 180F degrees … closed when I took it out of the pot … opened when I put it back in, etc.
Seems to be up to specs but I will replace it now that it’s out.
Coincidentally … 180F degrees was the temp of the radiator fluid when the car was up to operating temps and the temp gauge was in it’s normal position, which is halfway.
I have no idea how old the thermostat is.
I’ve only had the car for two years.

Has everyone forgotten that this was pretty normal drive-ability for cars with carbs ?

That’s what I said earlier, no problem . . . just drive it until it warms up in 2 minutes, 3 if it’s colder outside. If it bothers you, turn on the A/C and rear defroster and the rpms will drop a bit. Rocketman

What’s also important is that it closes completely. Some of the older OEM thermostats had a rubber gasket on the inner moving part to improve the seal. I would go to the dealer and get the right part and gaskets.