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Hesitating when cold

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by bigdaddy89, Dec 4, 2000.

  1. bigdaddy89

    bigdaddy89 1/2 ton status

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    For the last 2 weeks whenever my blazer is cold it will studer as if no fuel was getting to the injectors. I can let off the gas and just feather it so it will start getting fuel again. It doesn't matter how much fuel is in the tank. This only happens for about the first minute or two. Does anybody have any ideas? This is an 1989 350fi. I keep all the components on this vehicle up to date.
     
  2. Blue85

    Blue85 Troll Premium Member

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    It sounds like it is having problems running open loop. You might check your MAF or MAP sensor, whichever one it has. It could also be TPS. Do you have access to the trouble codes? For mechanical problems, it could be the fuel pump or fuel filter. I would guess that the injectors and O2 sensor are fine.

    "All right...who keeps squirting this oil in my driveway?"
     
  3. Emmettology 101

    Emmettology 101 3/4 ton status

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  4. 89K5

    89K5 1/2 ton status

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    I'm having the same problem. Today it did it the whole way to work, 30+ miles. There was a similar post a few weeks ago and most responses indicated a sensor problem. I can't remember which one though, I save the message and can't find it.

    Last spring I replaced the fuel filter, EGR valve, and O2 sensor only to find out it was only in the cold weather that the hesitating happened.

    Last week I took mine to a dealer shop to have it checked. They thought it might be a coolant temp sensor, but ended up only replacing a .75 cent vacuum hose. I was hesitated taking it to a shop because the weather would probalbly get warmer and it did! This weekend when it got cold, the hesitating started again. I'm going to start pricing some of the sensors and start replacing them. Let me know when you get it fixed.
     
  5. bigdaddy89

    bigdaddy89 1/2 ton status

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    I got down to 45 degrees. I had to break out my bear skin coat. Just kidding. I wonder if this problem has anything to do with the colder thermostat that hypertech sent me with the chip. I think I will put my other one back in and see if this might help. I am going to check my codes also. Is the top two ports on the right the ones I need to put the paper clip in to access the codes? I can't remember.
     
  6. Blue85

    Blue85 Troll Premium Member

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    The Hypertech Thermostat probably regulates your coolant temp to 180 or something instead of 195-200. It sounds like your hesitation problem is happening before warm-up is complete, so the coolant temp is below 180, right? Before you hit the opening temperature of the colder thermostat, it behaves just like the warmer thermostat (both are closed). So instead of swapping the thermostat, I would check and see if the Hypertech chip has some bearing on the problem.

    I had a car in high school that would bog unless I found a "sweet spot" in the pedal where the stupid thing would shoot some gas down the manifold. It was always the MAP sensor. I even carried a spare in the glove box. Pretty scary when you're trying to get out into traffic!

    "All right...who keeps squirting this oil in my driveway?"
     
  7. bigdaddy89

    bigdaddy89 1/2 ton status

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    It is actually a 165 thermostat. They claim I need to run the colder thermo to eliminate detination problems. I used to have a jet chip with a 175 thermo and never had this problem. It just started a couple weeks ago and its been cold for a while now, so I wonder if the thermo is actually the problem. What is the code for a bad map sensor?
     
  8. 89K5

    89K5 1/2 ton status

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    My problem is the same and I replaced the MAP sensor last night - no good. It was about 22 degrees this morning and it hesitated like it wanted to stall until it warmed up. Once warm it ran fine. NEXT
     

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