Idle at 4000rpm

[Gavin.reid]

Chevy 350. Okay so just got my project up in going fired it up after sitting a while and it would start at maybe 1500 rpm then all of a sudden rocket too 4000rpm what could be the causes? Have played with the idle screw doesnt matter if it's all the way in or all the way out same thing. The vaccum system is really messed up could that be all it is? What vaccum lines do I need and which don't I need?

Sent from my SM-N910H using Tapatalk

 

[HotRodPC]

How long has it been sitting? Is the throttle even touching the bump stop for the idle adjustment? Could be some junk has pitted, rusted or corroded and keeping the primary throttle plates from closing off.

 

[Gavin.reid]

How long has it been sitting? Is the throttle even touching the bump stop for the idle adjustment? Could be some junk has pitted, rusted or corroded and keeping the primary throttle plates from closing off.

Yeah it's touching it was sitting for 10 years I baught it got it running and then just pulled the engine to replace the clutch this week and now it has the crazy high idle

Sent from my SM-N910H using Tapatalk

 

[1987 GMC Jimmy]

You need to make sure that vacuum system is right. If the vacuum diagram is there, that's the tool you need. If anything off the manifold isn't being used, you need to plug the ports after you sort through it. The base gasket, EGR valve, or multiple leaks can cause issues. One time my carburetor bolts lost torque after a cold snap, and it was sucking in air under it. The idle was crazy high there. I'd put a vacuum gauge on it to make sure it's not an intake leak, either. I'd plug every port on the carb and intake to rule out the vacuum system and let you focus on the base gasket and intake. Then I'd resolve the vacuum system once your idle is correct.

 

[Gavin.reid]

You need to make sure that vacuum system is right. If the vacuum diagram is there, that's the tool you need. If anything off the manifold isn't being used, you need to plug the ports after you sort through it. The base gasket, EGR valve, or multiple leaks can cause issues. One time my carburetor bolts lost torque after a cold snap, and it was sucking in air under it. The idle was crazy high there. I'd put a vacuum gauge on it to make sure it's not an intake leak, either. I'd plug every port on the carb and intake to rule out the vacuum system and let you focus on the base gasket and intake. Then I'd resolve the vacuum system once your idle is correct.

Perfect thanks ill go buy all new vacuum lines for it all and then I'll delete the egr and efe system and just plug everything I'm not using.

Sent from my SM-N910H using Tapatalk

 

[1987 GMC Jimmy]

EFE's a little tricky. You can tie the valve open or weld it open. But yeah, I'd buy a vacuum cap kit or two from O'Reilly's and cap everything off to take vacuum accessories and emissions components out of the equation.

 

[Gavin.reid]

EFE's a little tricky. You can tie the valve open or weld it open. But yeah, I'd buy a vacuum cap kit or two from O'Reilly's and cap everything off to take vacuum accessories and emissions components out of the equation.

Yeah baught the kit from my local auto shop as I'm in Canada I might keep the efe then not sure

Sent from my SM-N910H using Tapatalk