98 silverado hard start when warm

Discussion in 'Chevy Truck Forum' started by Enraged Bacon, Dec 27, 2009.

  1. Enraged Bacon

    Enraged Bacon Full Member

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    I have a 98 silverado that starts perfect when cold. But when I drive it for a few miles and it warm up, when I go to restart the truck sometimes there is an issue, particularly before the thermostat opens and the engine is around 130F. The starter turns fast and the battery is new, but after the starter cranks the engine about 3 turns then the engine putts at me and the starter stops turning. I don't believe its the starter because it cranks fast, and the battery is new putting out around 12.7V.

    After the truck is fully warmed up and coolant is circulating through the entire system it also starts fine. So during the warm up process if I turn it off its hard to start. This leads me to believe it may be the coolant temperature sensor. The service engine soon light is on and im going to take it to my mechanic this week, but a sensor is only $30 and If that sounds like the problem to you guys I may go buy one and change it myself and see if that helps.

    PS wheres it located, Im currently searching for my repair manual and cant seem to locate it. 350 vortec.

    Thanks.
     
  2. davbell22602

    davbell22602 Senior Member

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    Pull the codes. Autozone or advance auto parts does it for free. I say if its not the coolant temperature switch. Then do a fuel pressure test. Might have a problem with the fuel pump, fuel regulator, fuel filter or the fuel pump strainer also.

    If its a 350 5.7L its right above the #1 spark plug on the drivers side of the engine.
     
  3. Enraged Bacon

    Enraged Bacon Full Member

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    P0161 is the code. Supposedly the second oxygen sensor on bank 2.
     
  4. davbell22602

    davbell22602 Senior Member

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    Is that upstream or downstream? But I would replace that first and see what happens.

    oxygen sensor heater circuit malfunction on convertor bank 2.
     
  5. Enraged Bacon

    Enraged Bacon Full Member

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    We have some bad snow around where I live, im going to wait until it clears up before I buy anything. Im guessing it may have been shorted out when I got a bunch of snow in the undercarriage yesterday, which is when the problem occurred.

    I don't understand how an oxygen sensor can prevent the engine from starting, I know if they are bad it can affect the performance and fuel economy of the vehicle, but not prevent operation. Maybe I'm misinformed.
     
  6. 1500cheyenne96

    1500cheyenne96 Senior Member

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    on those trucks there is two coolant temp sensors one on the block as dave stated and another in the thermostat housing either one can cause a problem like that if you can get it hooked to a scanner while it's running the scan tool will show whether or not one or the other sensor is bad a bad O2 shouldn't make it start hard it should as you stated make it run ruff and get poor gas mileage
     
  7. Enraged Bacon

    Enraged Bacon Full Member

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    #7 Enraged Bacon, Jan 15, 2010
    Last edited: Jan 15, 2010
    Sorry for the 2 week bump, but im having issues again.

    The engine light went out. But yesterday, it didn't want to start again. I finally got it started(i believe the fuel pump did not turn on, so it may be the relay as the pump is only 10 months old)

    It idles nice, and has alot of power under WOT, but when im just driving around town between 1300 and 2000 RPMS the engine seems to miss or stutter. No engine light came on and it was doing it yesterday and today.

    Yesterday i drove it about 30 miles on the highway and when i got to my destination the problem seemed to have stopped, and was gone the rest of the day.

    Today it started fine and I drove and it started stuttering and missing again between that RPM range after the engine started warming up. Im at a loss as what to do. It has only done this 3 times, and it only does it when its VERY humid outside and above freezing but below 60.

    Anybody have any ideas? I'm thinking some condensation could be forming somewhere it shouldn't be, due to the temperature and humidity and the engine warmth im sure condensation could form very easily.

    I know the engine is not getting fuel because if it were a spark issue the problem would persist at idle and higher RPMS.

    UPDATE:
    Just went for another drive, accelerating faster than usual. After about 5 minutes of driving like that the problem stopped. It also seems to happen ONLY in first and second gear under light throttle. Im going to take it to my mechanic on monday and have him hook up a scan tool to monitor whats going on, maybe he could figure it out.
     
  8. davbell22602

    davbell22602 Senior Member

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    Fuel pump can still be bad.
     
  9. mudseeker

    mudseeker Senior Member

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    #9 mudseeker, Jan 15, 2010
    Last edited: Jan 21, 2010
    sounds like you need a new cap and rotor.
    mine did this every time i let it sit over night or when it rained.
    [​IMG]
     
  10. vanhal

    vanhal Senior Member

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    hard starting

    you may just have to clean the distributor cap it will miss when it is very damp out

    mine did the pins where all coated with white powder cleaned it with brake clean and washed with soap and water ........... running great now
    run all the way from ontario, canada to florida pulling 6500 lbs. trailer andi have165000 miles on my 98 chevy 5.7l
    take care
    pete
     

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