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TBI Suging at idle when wet

Discussion in 'The Garage' started by kwissman, Oct 15, 2006.

  1. kwissman

    kwissman 1/2 ton status

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    My TBI engine in my 91 K5surges if I get it wet. It runs fine at higher rpms and will go away after a drive at speed. This seems to only happen when I get in water or sloppy mud. I thought it was the stock air cleaner sucking in a little water, but it happens at the car wash also. Any ideas where to look. It is kind of dangerous on the trail as it surges enough to try to move when you have the brakes on in the trail line.

    The engine is a stock 91 with headers and a heated 3 wire 02 sensor. It only does it at idle in park or gear. Seems to run fine if I have the accelerator opened up.

    Any ideas and help would be appreciated.

    Kent
     
  2. K5dreamer

    K5dreamer 1/2 ton status

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    could be a broken connector letting water in and causing electrical shorts.

    could be lots of things actually, hydrolock, yadda yadda.

    first things first, run the truck for codes. you can do it yourself with a paperclip or go to the dealership.

    if you dont know how to use a paperclip to flash codes, please ask and ill be happy to give directions.
     
  3. sandawgk5

    sandawgk5 3/4 ton status

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    Mine was surging and found out it was the TPS. It finally threw a TPS low voltage code. I swapped it out and no more surging. Your weatherpack connector for the TPS could be letting water get in a mess with the signal it is sending to the ECM therefore your surging.

    Ira
     
  4. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    check tps voltage at idle (truck need not be running, but key-on, engine off) when the throttle is closed, you should have about ..6-.8 volts, and with the throttle wide open you should have about 4.7-5.0 volts...
     
  5. mouse

    mouse 1/2 ton status

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    If it was hydrolock, his engine ingested water, and probably has a broken connecting rod or two...and that means it probably wouldn't run at all.
     
  6. kwissman

    kwissman 1/2 ton status

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    It is not hydrolocked. I can just drive through a water hole and it starts acting up. I will scan for codes and check the TPS. The check engine light is not on and it clears up after a 15 to 20 minute drive. Something must be getting wet and causing an intermittent short.
     
  7. K5dreamer

    K5dreamer 1/2 ton status

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    the hydrolock was a bad choice of words, i was just saying there could be several causes,

    also, even without a check engine light there may be codes stored in memory, so its still worth checking.
     
  8. kwissman

    kwissman 1/2 ton status

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    I checked the codes and came up with 42.

    The code means "The EST signal did not change when the ECM applied bypass voltage to the ignition module.".

    I checked the wires and did not see any cracks etc. Is Spark Control Module bad. They are about a $100, so I would like to make sure before I buy one.

    Is there a performance part for this or is it just the standard replacement available.

    Thanks

    Kent
     
  9. K5dreamer

    K5dreamer 1/2 ton status

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    bingo, i had completely forgotten, both my RS and my IROC had that throttle surge, put on a new ignition module in the distributor, and it solved the problem. the cost is way high though, mine was only like 50 bucks, check out www.gmpartsdirect.com
     
  10. diesel4me

    diesel4me 1 ton status Premium Member

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    moisture and ignition trouble =

    My first thought was "spark plug wires"..the #1 cause of poor engine performance on damp days or while raining..especially if it improves after being driven some,and they "dry out"...the distributor cap and rotor also can cause the same thing too,or a coil that's got a crack in it....sounds more like secondary ignition trouble to me,than a fuel or computer problem,but I don't know much about them--I suppose they could act up only when damp out too??...:crazy:
     

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