Throttle body

Asked by May 03, 2017 at 02:49 PM about the 1990 GMC Sierra 1500 C1500 SLE Standard Cab LB

Question type: Maintenance & Repair

I'm working on a 1990 gmc 1500 it runs good but
when it looses vacuum starts,to run really rough

1 Answer

24,455

You checked engine vacuum pressure? Is the intake leaking air? Is you brake booster good? Most time a vac leak causes high idle but if you are loosing enough to not have enough. There is many reasons it could run rough, from misfiring to throttle body/IAC dirty or bad loose electrical connections.

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