'89 SHO, will not idle correctly, really bad bucking and misfire under any load

Discussion in 'Gen 1 & 2 - Engine, Exhaust, Drive Line & AC syste' started by Jon, Sep 13, 2020.

  1. Jon

    Jon New Member

    Joined:
    Jul 26, 2020
    Messages:
    4
    Likes Received:
    0
    Location:
    Minneapolis
    Hey guys, so my newly aquired 89 SHO started to have rough start ups where it wouldn't idle, misfire and die. Would go away for the most part when warm. Now I left the car sitting for a month, tried to start it up, and the problem is now constant.

    It bucks and misfires and backfires under any load, AND under idle probably half the time. I'm thinking the Cam Position Sensor could be the culprit? The car leaks lots of oil on the belt side of the motor. I replaced the spark plugs and it ran a little better for about 3 minutes, then started to buck and not run well again.

    Any experience with these symptoms?

    Thanks all!
     
  2. zoomlater

    zoomlater SHO Member Supporting Member

    Joined:
    May 31, 2004
    Messages:
    2,194
    Likes Received:
    1,169
    Location:
    Seattle, WA
    sounds like a cam position sensor, but pull your codes to see if that is really the issue. my car would buck when driving when the cam position sensor failed
     
    Jon likes this.
  3. luigisho

    luigisho SHO Member

    Joined:
    Nov 2, 2001
    Messages:
    10,547
    Likes Received:
    3,386
    Location:
    va beach,va
    Home Page:
  4. Irish Pride

    Irish Pride Irish Inside Staff Member Super Moderators

    Joined:
    Dec 23, 2007
    Messages:
    2,612
    Likes Received:
    3,496
    Occupation:
    Owner of A Little Bit Of This And A Little Bit Of
    Location:
    MusicCityUSA
    Make sure you have the plug wires routed correctly. It's very common to get a wire crossed or use a manual that has the wires routed wrong.

    Engine
    1 2 3
    4 5 6

    Coil
    5 1
    6 2
    4 3
     
    luigisho likes this.
  5. Jon

    Jon New Member

    Joined:
    Jul 26, 2020
    Messages:
    4
    Likes Received:
    0
    Location:
    Minneapolis

    Thanks for the guide! I pulled the plugs again and there is definitely no major oil in the tubes, the threads of a few of the plugs were a tiny bit damp at most, but nothing of major concern. Valve covers are on the list, they seep a little bit. I'll go ahead and check those codes.
     
  6. luigisho

    luigisho SHO Member

    Joined:
    Nov 2, 2001
    Messages:
    10,547
    Likes Received:
    3,386
    Location:
    va beach,va
    Home Page:
    Pull those. Rechecking plug wire config is a good idea as posted above. go from there.
     
  7. FastCAD

    FastCAD SHO Member

    Joined:
    Feb 22, 2015
    Messages:
    125
    Likes Received:
    57
    Gender:
    Male
    Occupation:
    "cruisin'... into the sunset"
    Location:
    Miami, Florida
    Definitely check the plug wire sequence at the coil (an easy mistake). The (round) cam sensor cap; passenger side left of cam cover near the firewall is an easy check for oil leakage and fouling. If you don't get any codes then go to the
    (I )dle (A)ir (B)ypass (behind the throttle body). IAB does not throw a code. "Delphi- CV10140-11B1" Summit Racing $55.
    It is not likely that oil will foul the crank position sensor. A leaking water pump is another story. Valve cover gaskets-with plug well seals, manifold gasket set, cam seals and sensor gaskets (3 pieces) - RockAuto. Don't forget valve cover bolt gaskets "ShoSource".
    The SHO might burn a little oil like all ohc engines but oil leaks are not acceptable.:lol:
     
  8. rubydist

    rubydist SHO Master Staff Member Super Moderators

    Joined:
    Jun 25, 2007
    Messages:
    7,116
    Likes Received:
    3,007
    Location:
    Denver
    we need to know what the codes are or we are just providing wild speculation. please pull the codes and report what they are.
     
    shorage and SHOCH like this.
  9. shorage

    shorage SHO Member

    Joined:
    May 17, 2001
    Messages:
    244
    Likes Received:
    62
    Gender:
    Male
    Occupation:
    IT Security
    Location:
    Marshall, VA
    THIS

     

Share This Page

If you wish to help keep SHOforum running, please click the donation button below