idle up & down

[CivicVTi]

1994 GLXI lancer car, sir tulong naman po, pag start nang engine nasa 1500 rpm ko tapos after 30 mins pa bago bumaba nang mga 100o rpm, tapos may time na grabe up and down nang rpm bigla nalang namamatay engine, computer box kaya problem?
tnx.

Try mo muna palinis/palitan yung air filter element, baka sobrang dumi na at hindi makahinga mabuti ang makina. Palinis mo din yung idle air control valve (IACV) at mass airflow (MAF) sensor. Make sure na nasa good condition din ang engine oil at spark plugs pati na din yung high tension wires. Check din yung ignition coil at distributor, baka naglalangis na yung loob.