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Idle woes...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by det45, Jul 25, 2000.

  1. det45

    det45 1/2 ton status

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    Can anyone help me? I have a 89 K5 with a 5.7 TBI engine. My K5 always idled at a higher RPM momentarly when it is first started up and then would go to a lower normal idle. Now when I start it up, it stays at the lower idle and sometimes stalls. The engine runs well and has lost no power, just the idle will not go up momentarly when first started up. Some people tell me that the o2 sensor is going on the fritz and is giving incorrect info to the ECM. The fuel filter is new and injectors are good. Should I replace the sensor or look else where.......Thanks
     
  2. Casey 86K5

    Casey 86K5 1/2 ton status

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    I would check your O2 sensor first. It may be sending a false rich indication to the computer causing it to lean out and cause the low idle and stalling. A few other sensors may be causing this problem (TPS, coolant temp sensor, MAP sensor) but I would check the 02 before the others.
     
  3. coopertwpk

    coopertwpk 1/2 ton status

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    You have a bad IAC valve (idle air control) look at the left side of your TBI its towards the back has a four plug connector and is threaded into the TB unplug it and screw it out the install a new one also shoot spray carb cleaner into the hole to loosen up carbon form the pcv valve line.if it idles to high ill send you the instructions on adjusting your idle down but it should work fine.
     
  4. NYC K5

    NYC K5 1/2 ton status

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    id say your problem is most likely with the o2 sensor take it out and visually inspect it if it looks dirty you may be able to clean it and put it back in, it wont last as long but its a quick fix. my advice would be carburate it but i hate tecknology
     
  5. blazer72

    blazer72 1/2 ton status

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    IAC is what steps up the Idle but is closed when the motor is warmed up and they always seam to fail in when there closed. As for the O2 senser, Most folks dont replace them when they should! They need to be replaced just like plug, wires and the other stuff that dies after long hard use. And yes I know there are guys out there that are running 2M mile in the oem plugs, wires and such to you I say good luck !!!

    To make the truck run right replace the IAC to make it run good replace the O2 and the plus, wires, air fillters and such. [​IMG]


    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  6. realsquash

    realsquash 1/2 ton status

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    Yeah, I would check the O2 sensor first. But I think is is unlikely that the O2 is the problem. Check the IAC motor, like others said. You can remove the IAC and inspect the pintle for wear/stuckness. Don't force it around while it's off, just look at it.

    Is the check engine light (service engine soon light) on?

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  7. Blazer1970

    Blazer1970 1/2 ton status

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    I have never seen a new O2 sensor improve how an engine runs, mileage or anything else. Bosch would like you to think otherwise though. I guess they go bad, but I bet 95% of the ones that are replaced are fine. I agree on the IAC, see if it is carboned up, they can sometimes be fixed just by cleaning.

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  8. 87 mid canada k5

    87 mid canada k5 1/2 ton status

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    when my o2 went a while back, the truck had no power on the highway i could get her up to about 80mph behind a semi, but as so as i was on my own it would slow right down. this is with the go pedal right to the floor , it was just confusing the ecm on the fuel mixture. changed to a new one and problem solved! also i don't think the ecm even listens to the o2 sensor until it reaches about 600 degrees .
     
  9. blazer72

    blazer72 1/2 ton status

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    An O2 sensor is the maine point of the feed back that tell the ECM just how rich or lean the motor is running. And just like any thing other type of battery they get old and yes it is just that atype of battery, the unburned Ox in the exhaust cuses the rair metal in the senser to conduct the amount ot conducts tell the ECM just how rich or lean the system is and the ecm takes it from there. This is called running in closed loop. If the O2 senser is not working or is outside the limits then the system goes to open loop and uses more gas. I dont think that the life of the O2 senser is as short as Bosch would like us to think but they do get old and stop doing what they do.

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  10. det45

    det45 1/2 ton status

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    Thank you all for your replys! I did replace the o2 sensor and that fixed the problem. Not only does the engine idle normal, I jumped on the gas pedal and it took off like a scalded ape in a banana farm! The o2 sensor must have been going bad for a while because my K5 never responded like that until I replaced the o2 sensor. Thanks for your help you all.........Det45
     

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