high idle 96 5.7l

Discussion in 'Chevy C/K Truck Forum' started by RMortimer, Mar 25, 2014.

  1. RMortimer

    RMortimer New Member

    About two months ago my 1996 GMC C1500 5.7l would not immediately start. I had to give it a little gas to get it started. Once started, the truck would stall as soon as I shifted into gear. I replaced the Idle Air Control Valve, this seemed to fix the problem. Sunday before last I noticed an extremely high idle in park, approximately 2100 RPM. The idle in gear was about 1100 RPM. When I ran a scan, the P0102, Mass Air Flow Sensor code was returned. I replaced the sensor and all seemed fine. I did not drive the truck again until Wednesday. When I started driving Wednesday there was a bit of a rough idle and the Service Engine Soon Light illuminated. I ran another scan and this time P0175, system too rich bank 2, was returned. Feeling that it was too coincidental that I would keep having these kinds of issues, I reinstalled the MAF sensor, reset the computer this past Saturday. The vehicle idled fine, no Service Engine Soon, and no codes. I did not drive the truck too far Saturday. Sunday I drove the truck between 75 to 100 miles with no problems. I then drove the truck another 15 miles to and from dinner Sunday evening, no problems. Monday when I started the truck the high idle issue has returned. A scan returned no codes. Does anyone have any ideas?​

  2. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    WOW! Hard to read that gray on white!

    I would start by making sure the contacts in the connector are clean and making good contact and pack it with dielectric grease. When you wiggle or tap on the connector, does it make any difference?
  3. RMortimer

    RMortimer New Member

    All connection are good. Wiggling wires does not produce any difference. I plan to reset the computer again Wednesday when I have time to mess with it again and check for vacuum leaks.

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