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Does my 84 Blazer have a computer???

Discussion in 'The Garage' started by trev1981, Apr 6, 2007.

  1. trev1981

    trev1981 Registered Member

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    i have been having trouble with my blazer i bought a few months ago. It cuts out and sputters alot but sometimes it runs fine. I did a full tune-up and changed the fuel filter fuel pump. This made no difference, so i took it to a local shop that has made a good name for it self. the guy told me my truck has a computer in it and if something is wrong with it there is no way to fix it. Is this really true? What does this computer do and can i get a new one?
     
  2. darkshadow

    darkshadow 1 ton status

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    no you don't.

    unless the motor was swaped in with a computer
     
  3. trev1981

    trev1981 Registered Member

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    They said it does even thought it is carberated, i was shocked when they told me they said those years of chevys are a bitch to work on if something is wrong with the computer. should i take it somewhere else?
     
  4. broncoman6524

    broncoman6524 1/2 ton status

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    yes it does have a form of a comp...its for the knock sensor. but thats it as far as im aware of...some emissions bull****. on your dist if you have it off of the base thers a 4wire weather pack connector. unhook it and see hwat happens...its to the knock sensor btw.
     
  5. trev1981

    trev1981 Registered Member

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    if i take it off what should happen?
     
  6. broncoman6524

    broncoman6524 1/2 ton status

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    you elimate the knock sensor. if its bad and is retarding your timing or it truly is sensing a knock. it will NO longer retard your timing. :)

    on your dist do you have vacuum advance?
     
  7. 73K5Kid

    73K5Kid 1/2 ton status

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    My brother had an 86 3/4 ton and his 305 had a computer controlled carb. I guess early form of fuel injecion.

    LG4
    Years: 1980-1987
    The LG4 was the "low output" 305 in³/ 5.0L (compared to the L69). It produced 145–170 hp (110–127 kW) and 240–250 ft·lbf (325–340 N·m). The addition of a knock sensor for the engine management system in 1985 allowed an increase in compression and a more aggressive spark timing map in the ECM. As a result power increased for the 1985 models to 165 hp from the 150 hp rating in 1984.

    [edit] LO3

    Years: 1987-95
    The LO3 was the "low output" 305 in³/ 5.0L (compared to the 305 TPI LB9). It produced 170 hp and 255 ft·lbf of torque (185 HP @ 4,400 / 275 TQ @ 2,400 in 1993-1995 GM trucks). The 305 dropped the Computer-controlled carburetor and received the fuel-injected TBI (throttle-body injection). The TBI unit consisted of two barrels, much like those of a two barrel carb, but instead of "jets", there was a fuel-injector placed above each barrel, resulting in a 2-barrel, 2-injector setup. The TBI uses a unique injector firing scheme, for every rotation of the engine, each injector fired twice.
    TBI injection was used on trucks/vans through the 1995 model year, mainly because of its strong torque curve, allowing for heavy towing, hauling and taller axle gearing for fuel economy.

    http://209.85.165.104/search?q=cache:P8wmDyc2IR0J:en.wikipedia.org/wiki/Chevrolet_Small-Block_engine+1984+blazer+computer+controlled+carburetor&hl=en&ct=clnk&cd=3&gl=us
     
  8. trev1981

    trev1981 Registered Member

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    im not sure
     
  9. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    You should not have a computer. Last time I was up on this stuff, it was only 1985-86 CALIFORNIA only trucks that had the miserable computer controlled Q-jet.

    '84's aren't supposed to have it, but it's possible that you have a very early production model that was really an '85 but still slipped out as an '84.?.

    It's a terrible system, you get all the drawbacks of a carb still, along with most of the drawbacks of EFI, and NONE of the benifets of EFI.

    I basically tossed the whole get-up in the garbage with my '85.

    I see you are in California, about 30 minutes from me! I would highly doubt a shop would be dumb or crooked enough to tell you that you do have an ECM setup when you really don't.... Are you sure you have an '84? I am not suprised with what the shop said, most people don't want to mess with these things as there is NO aftermarket support and it costs a fortune to rebuild that miserable carb.
     
  10. trev1981

    trev1981 Registered Member

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    ya im sure it is an 84. The guy at the shop told me that mine was a federal so its not from CA. the CA 84 were better because they would throw codes so you could diagnos a problem, but the fed do not throw codes so its more a guessing game. i still don't know what this computer does. if it does spark could i just bypass it and get a MSD box?
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    Sounds like your shop guy is on the ball. Fed trucks won't have CCC. As an aside (poster, not really pertinent to you) I wouldn't say '84 CA trucks can't have CCC...I can only go back to '85 with my parts manual, but CCC was around since '80, (All GM US cars had it since 1981) so it's *possible* some CA trucks could have had it as early as '81.

    Anyways, there are two different ESC/EST setups. One simply monitors a knock sensor and retards timing if necessary. (when working correct) The *other* setup actually controls ALL of the timing. It's very simple to tell which is which. If your carb has a vacuum port on it, you have the "knock only" setup. If it doesn't have the vac port, you'd need a new distributor to get away from that system. :(
     
    Last edited: Apr 7, 2007
  12. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    The CA 85-86 CCC setup does two things.

    1. It completely controls the distributer, retardation, and advance.

    2. It tries it's best to minipulate the carb at IDLE only. There are a couple of sensors inside the carb and it uses timing and screws with the mixture trying to get the cleanest idle it can.

    Back when they were designing all of this stuff, the EPA had it figured out that emmissions were the worst at idle as far as pollutants, saying that there just wasn't the RPM's and air flow at idle to properly help kill certain particles.

    Your CCC setup is the best they could come up with for a number of years.....

    As far as using something like an MSD box to control timing, it won't work. You would need to get a vaccuum advance distributer and preferably a good 'ol 70's-early 80's Q-jet to go with it. You basically have to pull most of that stuff and replace it with normal 70's style parts to really get rid of it. Leaving the CCC in there with a vaccuum dist. will likely cause some funny idling possibly, and you'll have kind of a bastard system going on there.

    There is one catch..... converting like I did is illegal and you can forget passing smog for the most part with the visual inspection (tailpipe emmissions should be the same but who cares about that right?:rolleyes: ). That would be why I now have Montana plates on my K5.

    My number is 209-495-1212, I live in Modesto and am in the Escalon/Riverbank/Farmington area every day. I'd be happy to try and help you if I have the time.
     
  13. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    You might have ESC, electronic spark control. There is a computer for that behind the glove box, big shiny rectangular box. If you have the 4 wire weatherpack in addition to the normal HEI wires on the distributor, then you have ESC. You cannot just simply uplug that weather pak, the truck won't run. You can disconnect it and jump pins A & C (on the distributor side) and this will bypass the ESC and allow the vehicle to run. ESC only retards the timing if it detects knock, which is a very good thing. It allows you to run more advance and still evade knock, so you get the performace of more advance without the problems of knock.
    ESC is a great simple system, if it's working, there are rarely problems with it, and when there are, it's usally the knock sensor it self (easy fix, screwed into the bottom of the block somewhere either right or left sides), aside from that, it does take a special module for the HEI, which is very expensve if that needs replaced. THe ESC computer itself, I've never heard of that going bad, but there's a first time for anything.

    ESC is seperate from CCC, I don't know anything about CCC, you can tell if you have that if you have wires and weatherpaks on the carburator, aside from an elec. choke, non CCC carb will still have elec. choke.
     
  14. trev1981

    trev1981 Registered Member

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    well i guess i don't have CCCbecause my carb has elec. choke. well i guess ill try the knock sencor. Anything else i should try?

    Come to think of it i don't think there are anny wires coming from the card at all except for the choke. i'll have to check.
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    No, what he said was that CCC or non-CCC the same years, will both have electric choke. A CCC carb will have a TOTAL of 3 electrical connections to it...choke, TPS, and whatever the heck that solenoid is that controls fuel, that I have completely spaced the name of. :) (edit: mixture control solenoid, MCS)
     
    Last edited: Apr 10, 2007
  16. trev1981

    trev1981 Registered Member

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    oh ok i think i only have the choke wire.
     
  17. buffblazer

    buffblazer 1/2 ton status

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    if ya want to call the electronic spark control an early form of a computer than i guess you might say it has a computer. switch to HEI dizzy and it will fix your problem. your electronic spark control is probably screwed up and its retarding your timing. by switching to HEI you eliminate the ESP and it is a heck of a lot better. but thats just my 2 cents and if im wrong someone let me know
     
  18. dyeager535

    dyeager535 1 ton status Premium Member

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    Not really wrong, those ESC setups can certainly cause problems when they die. I knew someone that was having all sorts of problems, replaced distributor and problem went away. Of course, was it the ESC, or some other distributor piece?

    Only thing not quite right with your statement is that they are ALL HEI after points, just slightly different distributor setups: carbed, ESC/EST, fuel injected. :)
     

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