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328 Slow down light ECU rebuild?

Discussion in 'Technical Q&A' started by Cenzzo, Nov 5, 2003.

  1. Cenzzo

    Cenzzo Rookie

    Nov 5, 2003
    11
    Greetings!
    I'm up against the dreaded slow down light always on, which seems to be caused by a defective ECU as near as I can figure out. There are some really good postings around this, including one with pictures, which was excellent. It made me realize that, worst case, I can just disconnect it without hurting anything, although I'd have no warning system for a too hot cat!
    That being said, I'm considering just plain getting a test pipe to eliminate the cat, and the potential problem, altogether.
    In talking with a friend who's into Jaguars, he mentions ECU problems with them that were solved by someone disassembling the ECU's and "reflowing" the solder joints, and making them as good as new. That source he mentioned has dried up, so trying him will be no good.
    Has anyone heard of reconditioning them in this way?
    I just had to ask . . .
    Thanks,
    Vince
     
  2. hardtop

    hardtop F1 World Champ

    Jan 31, 2002
    11,211
    Colorado
    Full Name:
    Dave
    The slow down light is not associated with ecu's on 3.2 motors. It's just a thermocouple to detect too much heat in the cat.

    Dave
     
  3. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,161
    Texas
    Full Name:
    Steve Magnusson
    You guys are mis-communicating a little -- there's more than 1 "ECU". (but as hardtop said -- the warning light ECU doesn't communicate with the injection ECU on pre-348 F). My experience is that the F warning light ECUs are potted so you really can't even try reflowing the internal soldered connections (but yours may be different).
     
  4. jbanzai

    jbanzai Formula 3

    Feb 1, 2002
    1,564
    Madrid, Spain
    Full Name:
    Julio
    The thermocouple in the 328 is not connected to the ECU, but to a CCU unit. Is a small white resine 'brick'. This CCU is no computer, but it is still an electronic circuit, and it is incredibly expensive to replace ~2000 US$

    This CCU circuit seems to do a couple of things. One is indicates the ECU when to switch to close loop, that happens when the gases through the CAT are over 300 C. The second funcionality is to ground the Slowdown light when the CAT is over 900 C, turning it on.

    Check through the cable of the thermocouple. For a while I thought I had a bad CCU, but it turns out that the thermocouple steel cable had actually teared at the point where the cable goes into the trunk and it was making a bad conntact to GND, which was causing the Slow Down light to turn on.

    You can unplug the CCU, but then your car will be always running in open loop, so a bit rich. In the case that the CAT were going bad you will accelerate the problem and could lead into a CAT overheat and a fire hazard, without any warning.

    If you plan in removing the CCU, then replace the CAT with a test pipe to avoid the CAT fire hazard. I actually did this, but I am in Spain were cars manufactured before 1990 are not required to have CATs.

    - Julio.
     

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