Rough Idling: EGR, Spark Plugs, or Thermostat?

Discussion in 'General Motoring' started by GusTheCat, Jan 28, 2004.

  1. GusTheCat

    GusTheCat Guest

    Well, I have that 1989 Mazda 626 but it should be the same as a Honda.
    Six month ago the engine was idling rough, dropping from 750 to 550
    from time to time, and I get hiccups on highway. I brought it to the
    mechanic, and he cleaned the EGR valve, which was like a plugged pipe.
    The uneven idling was getting better, but not gone.

    Couple of days later, I pulled out the spark plugs, and found 3 out of
    4 have severe oily ash deposits. Changed the plugs and it got much

    Now I am wondering if a stuck-open thermostat could be the mother of
    all these problems? Our temperature is hovering around 35 F and it
    takes 4 or 5 miles to warm up the engine up to normal. I was also told
    that my car has more white vapor than other guys'. So I am suspecting a
    stuck-open thermostat. I just did not get a chance to pull it out.

    So here it is: plugged EGR, fouled spark plugs, engine running cool,
    and uneven idling. Is there some chicken-egg relationship between them?
    Any comments appreciated.
    GusTheCat, Jan 28, 2004
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