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rough idle

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by cbr929, May 11, 2002.

  1. cbr929

    cbr929 Newbie

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    I recently replaced the O2 sensor and TPS unit after getting numerous trouble codes (including EGR) regarding these. However, sometimes at stop lights, the engine idle is noticeably rough. I've heard that the gasket between the TBI and manifold sometimes goes out, causing an air leak. Has anyone had this problem? Have got no more codes since changing the afore mentioned parts. FI cleaner doesn't seem to do any good either. Previous maintainence includes new plugs, dist cap + rotor, dist module, and coil. Can someone enlighten me as to probable causes?

    '89 Jimmy/350/700R4/241
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Get it warmed up and get some kinda stuff like wd-40 or similar. Take it and spray it around any areas that you suspect. It will suck that stuff into the mixture and change the idle.
     
  3. GMMANIAC

    GMMANIAC Registered Member

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    If the gasket under your TBI were blown out you would have a high idle. You mentioned the EGR, did you get a code or did you replace it. If the EGR valve sticks open at idle the engine will run rough, likewise if it is leaking. The EGR vacuum control valve on my '89 gave me a similer problem you can check these with a vacuum pump. I had a plug wire that was only shorting out at idle also so if you have access to an engine scope you might check those also. Also check the spray pattern of your injectors, they should spray like a shower head.(thats not clogged up)
     

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