Announcement

Collapse
No announcement yet.

Idle Troubleshooting (semi long)

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Idle Troubleshooting (semi long)

    I have had a funky idle (revs drop to around 600 then up to 1k) for about 1 year now. Sometimes it will be fine, other times the idle is constantly irratic. The car seems to run okay during driving but every stop light, the idle would drop (near stalling) then kick back up to 1k rpm and continually do it untill I get to drive again.

    Unfortunately I think this problem took its toll on my fuel pump and it finally died about 2 weeks ago. I dont want to do the same thing with the new pump.

    I tried to do some troubleshooting this weekend. While doing the testing, the idle speed was fairly constant unless I removed something that would drastically change it.

    -I checked for any obivious vaccum leaks and installed the stock intake air box.

    -I tested the TPS (via the Bently manual) and the electronics seem to be in spec.

    -I removed the vaccum line from the FPR when the can was running and the idle speed increased (by sound) and when I replaced it, the rpms went back down.

    Now, the fuel pump has a slight buzz (not near as loud as the old one in its last dying weeks). There is a slight carbon build up on the inside of the exhaust pipes. When I first had the idle problem, I would hit the A/C button, and the idle speed would normalize. That trick stopped working but I found if I slightly (read: very very slightly) place my foot on the gas pedal at a stop light, the idle speed would normalize.

    PLEASE, does anybody have a suggestion on what I should test/change to finally put an end to this problem?

    Thanks so much in advance.

    BTW- the car is a 1991 318iC (M42) with 105k on the clock.

    Aaron

    #2
    Does the problem occur when the engine is cold? If not, I'd check the O2 sensor. I had a very similar problem with the M50 and it completely went away when I disconnected the O2 (which I replaced the next week).
    '91 318is
    sigpic

    Comment


      #3
      "When I first had the idle problem, I would hit the A/C button, and the idle speed would normalize. "

      You might want to check the aux fan. this happened to me when my aux fan stopped working. the only way to stop the fluctuating idle was to turn off the AC while idling.

      Comment


        #4
        clean the idle control valve?

        Comment


          #5
          The ICV was cleaned. I will check the O2 sensor.

          The first few miles idle normal. When the car starts warming up, the irractic idle is constant (600-1k). The fuel pump also seems to whine more or less depending on engine speed.

          Thank you for the suggestions.

          Aaron

          Comment


            #6
            Mate its ur O2 sensor...its dead...u can remove it and drive for a while, but note that ur car will eat alot of fuel and ur mornings will be dogs until it warms up again. its an easy thing to replace...ive done mine in the last 6 months
            Signature removed by R3V staff due to a violation of the forum rules

            Comment


              #7
              Mate its ur O2 sensor...its dead...u can remove it and drive for a while, but note that ur car will eat alot of fuel and ur mornings will be dogs until it warms up again. its an easy thing to replace...ive done mine in the last 6 months
              Signature removed by R3V staff due to a violation of the forum rules

              Comment

              Working...
              X