Misfire, hesitancy after rain or inactivity

Discussion in 'GM Powertrain' started by Johnny_Buchanan, Mar 28, 2012.

  1. Johnny_Buchanan

    Johnny_Buchanan Rockstar 100 Posts

    Red Dust ('89 350 tbi Sportside) is showing following symptoms:
    If not driven for a few days (or even one day if it rains or is very moist) the truck starts fine and runs ok for appr. 10 - 15 mins. but after that starts to hesitate and misfire (or idle speed starts to wary from very low to higher than normal). This continues for some time. Finally heals itself and does not happen again untill the next longer period of rest.

    Any ideas on what might be the problem, some sensor packing up or some moisture related problem somewhere?

    -J
     
  2. dedmon27

    dedmon27 Rockstar 100 Posts

    Well if it does it after its warmed up it does sound like a sensor. I assume there is no check engine light on. Only thing I can think of is hook up a scanner and read the live data. Good luck
     
  3. Johnny_Buchanan

    Johnny_Buchanan Rockstar 100 Posts

    Check engine light has turned itself on once or twice, but is not a regular sympton. It really seems to be happening in mid-warm state, after thermostate has opened up. MAF sensor failing, perhaps?

    -J

    Sent from my iPhone using Forum Runner
     
  4. Josh

    Josh Member 100 Posts

    if its had a code check what it was. my 94 had some problems aswell my map sensor went bad. it idled very strangely and bucked badly. also unplug the egr and cap the vac line first after you let it sit. see if its bad if problem disapears
     
  5. ippielb

    ippielb Epic Member 5+ Years ROTM Winner 1000 Posts

    I believe that the 89's being tbi have the knock sensor, and with moisture it can cause an incorrect reading. Just a thought.
     
  6. dualdj1

    dualdj1 Rockstar 100 Posts

    have you changed plug wires? The easiest way to tell, if it is moisture related, is to take a squirt bottle and mist over the plug wires, suspect sensors, etc, until you get it to act up. just make sure not to hit the dist.
     

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