88 truck, runs great with the map unplugged

Discussion in 'Engine Performance + Maintenance' started by lickmyburger89, Oct 8, 2018.

  1. lickmyburger89

    lickmyburger89 Newbie

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    looked up the prom. its for an 88 AKAT 1192
     
    Last edited: Oct 9, 2018
  2. Schurkey

    Schurkey I'm Awesome

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    I use an ancient Snap-On MTG2500. Similar to the MT2500. They're dirt-cheap on eBay, and getting them with software and cables old enough to scan pre-'99 domestic vehicles is pretty easy.

    Mine's getting a little flaky, though. I may be looking for a newer scan tool in the next year or so.
     
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  3. lickmyburger89

    lickmyburger89 Newbie

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    yeah, I've used one of these before. was a heck of a lot nicer than what i have. I am curious though, what would make mine produce a false code like was suggested on another forum? I've never gotten false codes off her before and has always lead me in the right direction for diagnosis.
     
  4. Schurkey

    Schurkey I'm Awesome

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    I can't help you with "false codes" except that it's either in the ECM or the scan tool.

    Given that the scan tool gives you MAP codes, and the vehicle won't run right with the MAP plugged in, I'd tend to trust the scan tool over the flashing light.

    Find another scan tool, one that requires some VIN input, and see what happens.
     
  5. lickmyburger89

    lickmyburger89 Newbie

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    That's what my thoughts were. guy on another was more insistent on it being the scan tool and that's why i was asking. I should have something,whether bought or borrowed within the week. I'm actually thinking the ecm myself. Signals were getting to the pin out once i tested to check for shorts.
     
  6. L31MaxExpress

    L31MaxExpress I'm Awesome

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    Just a word of advice when it comes to these trucks. Over the years I have run across some of them doing very whacky things electronically. Even had a friend throw an ECM in his truck at the advice of an independent shop. Most of the time I would find a dirty or broken ground connection on the top of the intake manifold by the thermostat or on the back of the head. Make sure the ECM has the proper grounds getting to it before condemning it.
     
  7. lickmyburger89

    lickmyburger89 Newbie

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    I made sure of the grounds before even considering. They're clean and i checked for shorts everywhere in between. my auto instructor always said to rule out everything before condemning any computer. i'm sure once i finally get something to view live data i'll be able to determine whether or not it's an ecm issue or something else. my biggest concern was whether i looked something over or not. i know something is telling the ecm to cut off the fuel when everything is plugged in. while running i can see the fuel cut off right before it dies plugging the map in.
     
  8. lickmyburger89

    lickmyburger89 Newbie

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    finally got her hooked up to an mtg2500 scan tool. got everything is situated and then when i turned the key on, the scan tool died out. also found a cheap 7747 ecm i picked up just to have but i have not messed with it yet. the grounds on the ecm checked out fine as mentioned before.
     
  9. Schurkey

    Schurkey I'm Awesome

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    What does that mean?

    My MTG2500 has a crappy rechargeable battery. When I crank the engine, it loses track of the vehicle it's plugged into. I have to re-enter the VIN data again after it's running.
     
  10. Madison Mehlhose

    Madison Mehlhose Newbie

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    There are 5 ground wires that terminate near the coolant temp sensor on my 89 are all 5 there on yours?
     

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