Surge at Idle

Discussion in '4.0 Engine' started by Nopedal, Sep 30, 2012.

  1. Nopedal

    Nopedal New Member

    I'm getting a very bad idle surge (lope) when my 1999 Ranger 4.0 (cam in block) is in park or neutral (auto trans). Don't have the problem when in drive or reverse. It almost stalls at the low end and sometimes does.

    I know it could be:
    Fuel pump/sending unit
    vacuum leak
    Idle Air Control Solenoid (IAC)
    Intake Air Temperature sensor
    Throttle position sensor
    Mas Air Flow (MAF) sensor
    Worn cam shaft,
    etc...etc...

    By the way, it has new plugs and wires.

    What is a knowledgeable persons first best guess?
    Oh, and it also idles a little too slow.

    Thanks,
    Nopedal
     
    Last edited: Sep 30, 2012
  2. Ranger Forum Sign Up!

    Join RangerForum.com Today - It's Totally Free!

    Are you a Ford Ranger fan? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's a great place for Ford Ranger Fans to meet online.
    Once you join you'll be able to post messages, upload pictures of your Ford, and have a great time with other Ranger fans. Whether your an old timer or just bought your Ford you'll find that Ranger Forum is a great community to join. Best of all it's totally free!

    Join RnagerForum.com Today! JOIN FOR FREE

  3. mcdonald58

    mcdonald58 New Member

    when did you start noticing this? also did you gap your plugs.
     
  4. OP
    Nopedal

    Nopedal New Member

    Been idling poorly for some time (year or more). Most likely I have a bad head gasket that is causing most of the problem (off and on). I've had a bleed down test done so looks pretty certain. In the mean time I used some additive to my antifreeze to postpone the inevitable. However, the really bad lope has only been going on for two to three weeks. I'm sure you're thinking I could have pulled something loose when I changed the plugs and wires, but that was about 12 weeks ago. Also, just checked that out a little while ago and all looks fine; no loose vacuum hoses or plug wires.

    Also, the plugs have been gaped. Anyway, unless they were really off, seems a stretch that a gap issue would cause this problem given that it runs great when in drive. At least as long as I keep my coolant level low enough to stop a lot of pressure build up that then causes water to get shoved into my leaking head gasket.

    I've moved my discussion over to the tech side for 6 cyl 4.0's.
     
    Last edited: Oct 1, 2012
  5. mcdonald58

    mcdonald58 New Member

    my truck was running perfect than i changed my plugs in hope of getting better mpg. they werent gapped properly and my truck has a rough idle now. i just need the time or money to gap mine or get new plugs.
     
  6. OP
    Nopedal

    Nopedal New Member

    Could be that a plug wire was slightly damaged during the plug change. Might try putting in a new set or getting the parts store to check any codes. Of course, it could be the gap, but unless it's way off, I'm thinking "not". But then again, I'm no expert on such things.

    By the way, I went back to the "ford" brand when I changed mine; man what difference. I'd tried some other brands for the gas milage thing too, but never really got the performance I wanted.
     
  7. mcdonald58

    mcdonald58 New Member

    yea only motorcraft or autolites are recommended for these trucks.
     
  8. OP
    Nopedal

    Nopedal New Member

    Lope at Idle

    I'm getting a very bad idle surge (lope) when my 1999 Ranger 4.0 (cam in block) is in park or neutral (auto trans). Don't have the problem when in drive or reverse. It almost stalls at the low end and sometimes does.

    I know it could be:
    Fuel pump/sending unit
    vacuum leak
    Idle Air Control Solenoid (IAC)
    Intake Air Temperature sensor
    Throttle position sensor
    Mas Air Flow (MAF) sensor
    Worn cam shaft,
    etc...etc...

    By the way, it has new plugs and wires.

    What is a knowledgeable persons first best guess?
    Oh, and it also idles a little too slow.

    Thanks,
    Nopedal
     
  9. OP
    Nopedal

    Nopedal New Member

    I've move my post over to the engine tech side for 6 cyl 4.0's.
     
  10. OP
    Nopedal

    Nopedal New Member

    Been idling poorly for some time (year or more). Most likely I have a bad head gasket that is causing most of the problem (off and on). I've had a bleed down test done so looks pretty certain. In the mean time I used some additive to my antifreeze to postpone the inevitable. However, the really bad lope has only been going on for two to three weeks. I'm sure you're thinking I could have pulled something loose when I changed the plugs and wires, but that was about 12 weeks ago. Also, just checked that out a little while ago and all looks fine; no loose vacuum hoses or plug wires.

    Also, the plugs have been gaped. Anyway, unless they were really off, seems a stretch that a gap issue would cause this problem given that it runs great when in drive. At least as long as I keep my coolant level low enough to stop a lot of pressure build up that then causes water to get shoved into my leaking head gasket.
     

Share This Page