News

My Testarossa engine cuts at 3800 rpm

Discussion in 'Boxers/TR/M' started by Dadster, Jun 29, 2020 at 1:21 AM.

  1. Dadster

    Dadster Rookie

    Sep 16, 2017
    10
    Full Name:
    S Evans
    Hi all,

    I have a 1990 testarossa and I am currently waiting for a mechanic friend of mine to look at it. I thought it might be good to consult the experts on this board before he does. Any thoughts or advice is appreciated.

    The car drives perfectly below 3800 rpm. Car has 22000 miles. It is in very good condition. All the cats are hollowed out. There are no warning lights on the dash. It has new fuel pumps, distributor, fuse box and other ignition related components.

    When you drive in any gear or under any load the engine will cut out when it reaches 3800 rpm...its like a rev limiter of sorts. If you rev the engine when in neutral then the engine also cuts out at 3800 rpm...the revs rise through it but then fall back down and the engine fires up again and it oscillates smoothly between 3500 or so to 4500 or so.

    The 3800 rpm is a rough estimate,,,it might be 3850 or 3900 but it is just below 4000.

    Maybe a wire is broken or a connection lose to the control units.? Is there a cold start limit that is not turning off.?

    Any thoughts appreciated,
     
  2. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    6,167
    southwest germany
    Full Name:
    romano schwabel
    not that I know

    can not imagine this.
    if it is handling like a rpm limiter as you write then I think you may first check the 2 sensors at the flywheel. I not think the problem are the ignition wires. may be the fuel pumps get stopped because of wrong infos?
    check if it is a fuel or an igniton problem. take a stroboscope light, connect to one cylinder and let the engine run, accelerate and when the engine then stalls have a look if the strobelight still is flashing.
     
    brian.s likes this.
  3. Veedub00

    Veedub00 F1 Rookie
    Silver Subscribed Owner

    Jun 30, 2006
    3,669
    Troy, Michigan
    Full Name:
    James
    I'd make sure those 2 electrical connections underneath the coolant reservoir are clean too. Those signals go through them.
     
    vincenzo and turbo-joe like this.
  4. Ianjoub

    Ianjoub Formula Junior

    Dec 22, 2019
    496
    Homosassa, FL USA
    Full Name:
    Ian Joubert
    I think he means a timing light on a plug wire. You can also get a set of noid lights to see if injectors are getting signal.
     
  5. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,056
    Texas
    Full Name:
    Steve Magnusson
    No electrical signal used by CIS injectors, but agree that the logical first diagnostic step would be to just confirm/deny spark on both banks when the problem occurs.
     
    Qavion, Ianjoub and turbo-joe like this.
  6. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
    2,761
    Upon hearing this:
    “All the cats are hollowed out.”

    It reminds of the first ‘major’ that I paid an independent professional to do. He claimed the precat was damaged and he hollowed it out as a ‘repair’.

    Later, FoS said that the car would not meet emissions standards on a gas analyzer. They diagnosed it as bad cam timing. They were correct. The bad timing had put excess fuel through the cat and burned ‘em up.

    Several sequential things I would check to address your issues:
    1) Check connector under your expansion tank to ensure it is clean and tight.
    2) Check plug wires for continuity and resistance. Check inside your distributor caps for any carbon tracking or dirt/oil as well as the center button.
    If that fails to fix it....
    3) Get a gas analysis to ensure everything is right. This is only suggested because of your hollowed out cats.
     
  7. Ianjoub

    Ianjoub Formula Junior

    Dec 22, 2019
    496
    Homosassa, FL USA
    Full Name:
    Ian Joubert
    Just read up on these, learn something new every day!

    https://en.wikipedia.org/wiki/Jetronic

    "Fuel is pumped from the tank to a large control valve called a fuel distributor, which divides the single fuel supply line from the tank into smaller lines, one for each injector. The fuel distributor is mounted atop a control vane through which all intake air must pass, and the system works by varying fuel volume supplied to the injectors based on the angle of a moving vane in the air flow meter, which in turn is determined by the volume of air passing the vane, and by the control pressure. The control pressure is regulated with a mechanical device called the control pressure regulator (CPR) or the warm-up regulator (WUR). Depending on the model, the CPR may be used to compensate for altitude, full load, and/or a cold engine. The injectors are simple spring-loaded check valves with nozzles; once fuel system pressure becomes high enough to overcome the counterspring, the injectors begin spraying."
     
  8. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    6,167
    southwest germany
    Full Name:
    romano schwabel
    when you test then disconnect the O2 sensors
     

Share This Page