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Bogging off idle

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BigBadJap, Aug 13, 2003.

  1. BigBadJap

    BigBadJap Registered Member

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    Hi, the new motor is installed and running great BUT it seems to be running fairly rough at idle, and there is a very short delay before it picks up from a standing stop. I set the timing with the brown wire disconnected and set it to 0*. New spark plugs, cap and rotor; and she pulls like a demon after the short delay and no engine codes are coming up.

    Any ideas on what could be causing this?
     
  2. chevystepside

    chevystepside 1/2 ton status

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    try resetting the timing with wire diconnected and instead of setting at 0deg. Advance it to 4deg.
     
  3. sled_dog

    sled_dog 1 ton status

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    definetally sounds like you need a few degrees added on the timing.
     
  4. BigBadJap

    BigBadJap Registered Member

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    I'll give that a try. I asked a similar question in an earlier post, and I was told to set it at 0* advance since it's fully electronic ignition. I guess if it's not pinging, it should be fine.
     
  5. sled_dog

    sled_dog 1 ton status

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    how do you like 3.42s with 33s? same seutp I will soon be running. Also if that doens't do it mayeb your running a little lean or something, try changing the fuel filter maybe.
     
  6. BigBadJap

    BigBadJap Registered Member

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    With it bogging from stand still it doesn't seem that good. Once it gets a little higher in the rpm range, it goes good. Even with the bigger tires, it's still a lot quicker than the old motor.

    3.42's definitely aren't ideal for 33's. My rear end is ABOUT to go and I'm thinking of going to 4.11 or 3.73. I believe 3.73 and 33's will put you pretty close to stock ratio.

    The biggest problem with the 3.42's and 33's is that you can't use OverDrive until 110kph/67mph to avoid lugging and burning up the tranny; and you can pretty much forget about towing.

    Haven't checked the fuel filter yet - but I would hope that since it's fuel injected, it would compensate for a lean idle condition.
     
  7. crazykev4x4

    crazykev4x4 1/2 ton status

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    ru running TBI? also r u running headers? if so u should have a heated oxygen sensor instaed of the one wire . i just installed my heated o2 tonight and no more hesitation or bog.

    Kevin /forums/images/graemlins/k5.gif
     
  8. sled_dog

    sled_dog 1 ton status

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    Yeah well I have the 465 and no O/D. On 700R4s I never shift into OD until like 70 anyway.
     
  9. BigBadJap

    BigBadJap Registered Member

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    I have a brand new O2 sensor.

    I guess it could be that the computer hasn't adjusted to the new conditions yet either.
     
  10. sled_dog

    sled_dog 1 ton status

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    computer shouldn't need to adjust. Mine never went through an adjust process after I disconnected teh battery for hours and changed the exhaust and intake.
     
  11. BigBadJap

    BigBadJap Registered Member

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    If you're an 84, you wouldn't be fuel injected, so your computer wouldn't/couldn't adjust air/fuel ratio anyway. (Unless of you've added efi)

    I haven't had a chance to try advancing the initial timing at all. I'll try it when it comes back from the gear shop... grrr stupid rear end...
     
  12. BigBadJap

    BigBadJap Registered Member

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    Well, I've been running the truck for a while now. I am finding that it behaves better cold. No hesitation. Yesterday, I took it for a short warm up run, and when I got back, I noticed:
    A) There is a hesitation at low RPM
    B) It doesn't idle right. It revs up, then falls off then cycles that over and over again. Do you think that the supposedly "computer friendly" cam I put in is wreaking havoc with manifold pressure sensor?
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    That cam doesn't appear to be "wild" enough to cause vacuum problems.

    But, without watching what the engine is doing, you'll be guessing as to whether the cam is the problem or not. A "burned" chip for your combination would perhaps also help.

    The difference warm/cold is (my guess) open loop vs. closed loop, since closed loop works off of pre-programmed ("fixed)fuel/timing maps. But that could be ANYTHING, not just the cam.
     
  14. sled_dog

    sled_dog 1 ton status

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    206/214 @ .050", 249/260 duration at seat to seat, .434/.444, I really don't know the limits on cam's but I don't think thats too big for stock setup. Like was asked before do you have headers? If so did you replace the O2 sensor? I know you said you have a new one but is it the standard 1 wire style? Heated really does make a difference and if you don't know what a heated is ask man. Really sounds like there is a wrong signal somewhere and the fact that it happens when it gets warm is making me think O2 as well.
     

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