The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 1999 Vortec 135k mi hesitates at hwy speeds...

B. W. · 07-28-2018, 12:54 PM

I've had that issue several times on different rigs. It's usually the intake manifold gaskets failing. The engine will also be going through a little coolant. If it's setting a 420 code & no misfire codes it can be the pressure regulator (it's inside the manifold on the side of the spider)

07-28-2018, 12:54 PM	#2
B. W. Registered User Join Date: Nov 2014 Location: Bigfork, Montana Posts: 1,137	Re: 1999 Vortec 135k mi hesitates at hwy speeds... I've had that issue several times on different rigs. It's usually the intake manifold gaskets failing. The engine will also be going through a little coolant. If it's setting a 420 code & no misfire codes it can be the pressure regulator (it's inside the manifold on the side of the spider)