Rough idle and bubbling noise under cab

Asked by Jan 19, 2017 at 11:34 PM about the 1991 GMC Sierra 1500 C1500 SLE Extended Cab LB

Question type: Maintenance & Repair

I have a 91 GMC Sierra 1500 5.0 .  It idles
rough at low speed sometimes  stalling .
Runs  fine  at a higher speed .  There's also
a bubbling noise under the cab  like it's
coming from the muffler . But the noise
doesn't always happen .  I have changed
the idle  control valve PCV valve and  fuel
filter .

2 Answers


Maybe you have a exhaust leak. Take it to a muffler shop. The rough idle could mean you need a tuneup or that the IAC is dirty or needs replacing.

What is the idle at? Maybe try running a can of sea foam through it

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