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Thread: Newbie here with a 2+ year problem

  1. #16
    LT1 specialist steveo's Avatar
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    you changed your engine and not your ECM, and the engine is effectively the same engine? proms don't change themselves, and if they do, it's considered corruption and they throw a checksum error (so you'd know by now)

    keep lookin'

  2. #17
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    Quote Originally Posted by pmilne View Post
    The more I think on this, the more I am thinking prom. If I can find one to try, anyone that will run a 350. I dont even care about drivability. Just something to try.....
    Get the ecm number. The ecm is right behind the glovebox. Putting wrong prom and ecm together can result in bad things.

    A bad prom turns the check engine light on right away, causes the engine to run poorly with a lack of power all the time. You can't talk to the computer with a code reader and disconnecting the timing connector doesn't make a difference because the ecm won't be controlling timing. Spark timing will be at the original setting until around 2500 rpm where it will suddenly jump up 10-12 degrees. You can see it do this with a timing light.

  3. #18
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    In the meanwhile: https://photos.google.com/share/AF1Q...dTclZOak9IZm5R

    Kinda hard to hear much but you surely can hear it sucking air. That IAC must be wide open.

  4. #19
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    Agreed. Is that with the distributor fully connected and set at 6 degrees?

  5. #20
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    That is correct.

  6. #21
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    Definitely something funny there. Adding or subtracting timing makes it worse. It smells rich but struggles to run like it's lean. I'm still leaning away from electronics. You can usually force those old systems to do what you want for a limited time. But this engine seems to need more of everything. You could try finding a way to add a little fuel while it's idling rough. I know it smells rich, but I've seen cases where running lean just doesn't burn enough of the fuel to clean it up.

  7. #22
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    Sure, you give it throttle and it cleans it up, 1500-2000 rpm probably.

  8. #23
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    Something killing spark to one hole, temporarily? New wires, new plugs dont help.

  9. #24
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    Didn't sound like a dead hole. And I'd think you'd feel it. Especially if you shift into drive.

    Hate to say it but it really sounds like the '80s carbureted engines. It was a real bear to get them to idle right.

    Just thinking about this, is your EGR valve connected?

  10. #25
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    It is. I've checked it for leaks too. What are you thinking? Remember, its still only for those 30-40 seconds. ;)

  11. #26
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    Sure... EGR slightly open can cause problems. When ecm is warmed up it can cover for many small issues. It's not likely to be EGR but I'm just covering all the bases.

    30-40 seconds, sure, but still needs six degrees extra timing, too.

  12. #27
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    I've carb cleaned everything looking for leaks. It doesnt per se "need" it, it just likes it better, its more free. Like any small block Chevy I have ever dealt with.

  13. #28
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    Heres pix. Mind you, the box was changed as a test.

    Hopefully the number you want is there. I googled those numbers but come up with nothing....hmmmm.

    https://imgur.com/a/opcbAQ7

  14. #29
    Fuel Injected! jim_in_dorris's Avatar
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    Well, BHRD is the mask is on the ecm. That is a 94 l van. 4.3l v6 CPI $0D mask. I can't read the blue memcal but something isn't right. I see you changed the ecm, but not sure what the mask printed on blue memcal is. Was the memcal out of your original ecm? what numbers are printed on the original ecm
    Last edited by jim_in_dorris; 11-04-2018 at 06:19 AM.
    Square body stepsides forever!!!

  15. #30
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    Quote Originally Posted by jim_in_dorris View Post
    Well, BHRD is the mask is on the ecm. That is a 94 l van. 4.3l v6 CPI $0D mask. I can't read the blue memcal but something isn't right. I see you changed the ecm, but not sure what the mask printed on blue memcal is. Was the memcal out of your original ecm? what numbers are printed on the original ecm
    The ecm was a donor that I tried. The memcal is the one that has always been in there: 1263167

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