Rough Idle

[DIYER]

Need some help w/ 2002 GMC Sierra 1500 5.3 engine- about 116,000 miles:

Idles at about 600 RPMs boges down to about 400RPMs. Codes displays bank 1 &2 lean. Changed plugs, wires, Air filter & PCV value. Had fuel pump & filter changed month or 2 ago.

[GMstrong]

Look into your fuel pressure regulator.Pull of the vac line off the fpr and see if you smell gas in the line its more then likely bad.Or even worst if you have actually gas in the vacuum line like my 99 sierra does have to change to ASAP its been way too cold to do it since i have no garage or nothing.

[8.1HD/ALLISON]

If the fuel pressure regulator was leaking it would show running rich. I would just about bet your intake gaskets are leaking. Take some propane or choke cleaner and spray where the plastic intake meets the cylinder heads and see if the rpms change.

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......or your maf is dirty or bad.