Hi, I own a 1998 Civic. In the past few weeks the engine fails to catch up speed in the first 3 seconds of a cold start. It shakes badly during that period. After those 3 seconds, it normally goes up to warming up idle speed, around 1500 RPM. Never happens on warm or hot start. Air temperature during the mornings is around 65 degrees fahrenheit (18 celsius). When it started to develop the problem some weeks ago, it was a mild shake, but now is very harsh and rough. MIL has never turned on, nor the ECU gives any code when using the service check connector.

I always let the fuel pump to work a few seconds before cranking the engine. Spark plugs, air filter and gas filter were all replaced about 500 miles ago (less than 1000 Km). I know it can be anything from fuel pressure problem, MAP sensor, temperature sensors, Idle air control valve... but I don't know where to start

Any clues?

Thanks in advance

 

welcome to the forum. Check the cleaness of the throttle body. Do not spray carb cleaner into the induction chamber. fuel injectors may need cleaning.

 

I'm waiting for the weekend to check dirt in throttle body, but I had time to perform a quick experiment (I did it twice, one each morning). I unplugged the idle air control valve connector, and cold-started the car. It started up just fine, idling at normal idle speed at first, then gaining a bit of RPM while warming.

Does the fact that I removed the valve and didnt shake gives more clues to pinpoint the problem?

Thanks again for the help

 

check and clean the idle control valve,( you did a good check ), the throttle control valve is probably good. If after cleaning the ICV and the idle contiues to be rough, then it may be the sensor.