It doesn't die everytime but sometimes it idles so low that I can't even tell the car is on. I ran a diagnostic and came up with nothing. What could be causing this?

99 EX

 

Is the low idle problem only when the engine is cold?

What do you mean by you ran diagnostics? Is this to say that the CEL is not ON?

Some possible fixes include:

(1) Cleaning the IACV with carburetor cleaner, (2) adjusting the idle speed, (3) checking for a problem in the IAT sensor circuit, or (4) changing you air filter.

 

the CEL is not on because I turned it off a few days ago when I got the P0420 code to see if it would come back on. So when the car died today the CEL was not on but I ran a diagnostic anyways to see if there were any pending codes which there weren't. This is the first time it started doing this and I don't think it's just because it's cold because I've driven it on much colder days and today is fairly warm.

 

I wasn't referring to cold as the air temperature outside but rather the engine temperature. Does the problem only occur before the engine has warmed up based on the temperature gauge in your instrument panel?

 

I had the same problem and it turned out to crack header. I assume that the crack header would create a lower back pressure so the engine runs abnormal. I disconnect the battery and reconnect it after few minutes so the ECU can relearn to deal with that crack until I get the header replace. Sounds odd but it worked. The only difference between yours and mine is that I had and still do have CEL on.

 

this actually happened to me before on a 97 LX it turned out to be an A/C belt that was badly wornand creating some serious slack/tension on the engine. I didn't notice until i turned the car off where the worn part on the belt was visible. I got my pocket knife and cut the belt off right there and went on my way. I didn't believe it at first but thats what it was.... i replaced the belt a few days later and all was good