1972 145 D-jet very rough cold idle

Discussion in 'General Motoring' started by Gary Heston, Oct 21, 2003.

  1. Gary Heston

    Gary Heston Guest

    Greetings;

    I had some work done on my 145 back around February when the fuel
    system went berzerk and was spraying _way_ too much fuel.

    $495 plus a few parts I provided later, I had a driveable car again;
    however, they were not able to eliminate a very rough idle when cold.
    She starts promptly, but chugs like a steam engine for the first few
    minutes; if I step on the accellerator, it chugs worse and frequently
    dies. If I go really slow on the accellerator, it won't act up, but
    will start firing normally and run smoothly as long as I keep it off
    idle.

    When I was under the hood this summer, I noticed that the idle stop
    screw was down against the stop, holding the butterfly open quite a
    bit more than I think is normal.

    Once warmed up, she runs normally (although at about 13.5MPG). If
    it's only been an hour or so since shutdown, there's no problem.

    With the cooling weather, the problem is more pronounced, and it's
    getting annoying. The original work involved replacing the MPS (selected
    from four used ones that I obtained; they aren't made any more), the
    pressure regulator, and a temperature sensor.

    Anyone have any suggestions as to what might be causing it to act
    like this? With the idle stop screw all the way down, it's clearly
    running rich at cold idle. I'm open to suggestions...

    Thanks,


    Gary
     
    Gary Heston, Oct 21, 2003
    #1
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  2. Gary,

    The catch with driving a 25 year old and older car is you need to find a
    mechanic that has been mechanicing longer than that!! ;o) It is better if
    you do your own maintenance,

    OK. The best thing I can recommend is you buy a book or two about bosch
    fuel injection and basic automotive wiring. The D Jet really isn't that
    complicated, but the under the hood parts have been abused due to the
    environment they are in. (A fuel hose split on me recently) The CPU is
    essentially bullet proof.

    You need to do several things, since somebody has obviously screwed up the
    system. The timing should bve set first, so you know that variable is not
    affected things. If you are thinking about passing up this step, then
    forget the rest. Don't be scared off by needing the special "tool" for the
    air intake. You can make your own from a peanut butter jar lid or anything
    else similar.

    Check the wires/connectors going to the temperature sensor. (One
    disintigrated in my hand last year) Look at the wores carefully all the way
    to the fire wall.

    Check the wires going to the cold start valve.

    Check the resistance on the temperature sensor. Hot and cold. can't
    remember the spec off hand. You can probably get it from the brickboard or
    ask at the 1800 list.

    The butterfly should be closed when the gas pedal is released. There could
    be an issue with the cable.

    The throttle position sensor needs occasional cleaning. A pencil eraser
    does the trick. Just be cautious.

    I hope the last mechanic did not jack up the fuel pressure. Checking the
    pressure at the fuel rail is a little more detatiled than most folks are
    prepared for, but is an outside chance.

    good luck

    chuck petterson
    73ES
    ex 142E, 1973-1982 121xxx miles
     
    Support Your Community Band, Oct 21, 2003
    #2
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  3. Gary Heston

    Mike F Guest

    I found on my old D-Jet cars, many years ago the best thing to do is
    eliminate the idle circuit. Among other problems it gets rid of that
    lurch that occurs when the computer switches from the idle to the
    running circuitry. If you unplug the throttle switch, you can see what
    happens. This eliminates the acceleration enrichment as well though, so
    the "real" fix involves disconnecting one of the wires for the idle part
    of the switch.

    P.S. I sold my last D-Jet Volvo in 1985!
     
    Mike F, Oct 21, 2003
    #3
  4. Gary,

    Don't be too overwhelmed by mysteries of D-Jet. Many problems are
    mechanical and/or loose wiring/poor grounding.

    The hints you give relate to temp change. If you have not replaced the
    injector seals in last 3 years, it's time. Each injector has 3 seals, which
    may be hard, brittle, cracked. When cold, these don't seal. When warmed,
    these may expand and cause a little tighter (but not great) seal.

    Another temp related part is the aux. air regulator. You may have mentioned
    this already among the $495 in parts. Don't overlook the hoses to this
    part. If old, dry, cracked, or if you don't know how old, it's time to
    replace these, as these also can behave differently with temp change.

    The short sections of rubber fuel line hose along the fuel rail to each
    injector may be another source of problem. If old, dry, cracked, of if you
    don't know how old, you know the rest.

    The hose between the intake and the air pressure sensor - is it old - you
    know the rest.

    Check the joined ground wires between the injectors and the ground terminal
    on the intake manifold. Be sure this is a good, solid, clean connection.

    Double check all the connections from the injectors wiring harness to the
    each injector.

    After you've completed the above, it's time to check your ignition timing,
    and set it correct. Peanut butter jar lid has become the D-Jet Expert's
    correct tool of choice for controlling the idle RPM.

    That's most of the very simple, very cheap, and correct sequence of
    troubleshooting that I can think of. I'm no expert, so I must concentrate
    on mastering the simple things. Usually, D-Jet is well maintained by just
    focusing on the simple things: seals, hoses, and ground connections.

    Pat Q
     
    Pat Quadlander, Oct 22, 2003
    #4
  5. Gary Heston

    Gary Heston Guest

    I'll dig out the owners manual and see if I can track down that wire. I
    do have a replacement TPS--new old stock; still in the original box.

    I'm not sure I'm worried about acceleration enrichment; it's already
    running too rich.
    I probably should have sold this one last year instead of putting tires
    on it; since I didn't want to waste the $550 in new tires, I decided to
    go ahead and have the front end redone ($2100 at the shop plus about
    $600 in parts I provided), then the fuel system... I'd have been better
    off in may ways to just buy a newer Volvo.

    However, nobody pulls out in front of me... :)

    Thanks,


    Gary
     
    Gary Heston, Oct 22, 2003
    #5
  6. Gary Heston

    Gary Heston Guest

    The shop I took it to was owned by a guy who had worked on 140 series
    in the past, and still had the factory manuals for them.
    Which books?
    I'll see if I can get under the hood this weekend and take a look at it;
    wasn't aware of any special tool being needed.
    I'd have thought if that wasn't working, it'd run lean. Will look at
    it as well.
    Probably in my Haynes book; I think I have a spare one.
    There's slack in the cable. The idle stop is definantly cranked all the
    way down.
    I have a NOS TPS, I may just go ahead and swap it. I think I have a
    link to a web site that includes TPS adjustment instructions.
    I don't have a gauge suitable for that; the regulator was replaced,
    though.
    Thanks


    Gary
     
    Gary Heston, Oct 22, 2003
    #6
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