1. Welcome To GMTruckClub.com!

    The #1 Chevy Truck Forum Online
    Online since 2004, we are the #1 Chevy Truck & SUV forum and user community. If you have any questions about your Chevy or GMC Truck, SUV or Crossover, or just want to connect with other GM owners and enthusiasts around the world, you've found the best place on the internet to do that.

    Join Today ~ It's Free
    Registering is Free and Easy! Hope to see you on the forums soon!

Idle Stumble

Discussion in 'Chevy C/K Truck Forum' started by kcfocus1, Jul 28, 2011.

Random Gallery Photos

  1. kcfocus1

    kcfocus1 New Member

    My 1990 305 1500 runs great..... just put in new timing gear set and distributor along with fresh valve grind.
    Everything is whiz bang until I reconnect the timing bypass wire, then it stumbles and stalls out if left to just idle.
    Any input?
    Last edited: Aug 10, 2011
  2. Ethan

    Ethan New Member 100 Posts

    Did you time the engine correctly? Make sure your crank position sensor was working?
  3. kcfocus1

    kcfocus1 New Member

    1990 no crank sensor and yes timing is correct.
  4. Ethan

    Ethan New Member 100 Posts

    If it has a PCM it has a crank position sensor, you just got to look for the thing, it's the only real explanation of why it stalls out when you bypass the...timing bypass wire? Why do you have to bypass that? Now I don't get what you are doing...

    Ok, so the truck runs great, until you bypass the timing wire...which is connected to the crank sensor to determine the actual timing of the truck..well of course it would die if you bypass it, if the PCM no longer has the crank sensor position, it doesn't know when to inject fuel and when to tell the ignition coil to fire.

    Idk, that's my best guess, unless you did something wrong.
  5. kcfocus1

    kcfocus1 New Member

    My truck is a 1990 Chevy 305 aren't crank sensors included in OBD 2? My truck is OBD 1. Also truck runs grear with bypass disconnected..
    as soon as I connect it the idle starts to stumble and it will stall out. I see fuel being sprayed during reconnect and intill it stalls. Thanks
    for any input. Am driving it for five days with bypass discoed cause I hate using the starter motor at each red light.
  6. kcfocus1

    kcfocus1 New Member

    Does anyone have any input I may exercise on this stumbler?
  7. Ethan

    Ethan New Member 100 Posts

    OBD 1 still uses a crank sensor, how else would you and your PCM read RPMs? Sounds like you messed something up electronic wise, might not the be crank sensor, but I don't know anymore, I'd just take it to a shop, or ask this question in the powertrain sub forum.
  8. cland

    cland New Member

    OBD-1 has no crank position sensor, it uses the pickup coil in the distributor
  9. kcfocus1

    kcfocus1 New Member

    Now that we have established that Any suggestions to the cause ?
  10. cland

    cland New Member

    Double check to make sure your not off a tooth when you stabbed your distributor.

Share This Page