Engine RPM's - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1984Silverado4x4 · 01-24-2009, 02:44 PM

My truck has a 305 with the stock Quadrajet on it and a 4spd transmission.
When I drive a vehicle with manual transmission I sort of expect the RPM to drop back to idle speed as soon as the clutch is disengaged. On my truck however when I disengage the clutch (depending on how fast im going, what gear im in, and engine temp) the engine will rev way up for a few seconds then settle down to idle. Couldnt tell you what it revs to as it dosent have a tach but I imagine 2500RPM or so.

It happens the worst when the engine is cold and im only doing 25mph in 2nd gear and come to a stop sign or something.

Anyone have ideas on why it would do this?

Restrorob · 01-24-2009, 07:42 PM

It sounds to me that you could have a vacuum leak somewhere, Maybe a loose/cracked vac. hose or possibly intake ?

piecesparts · 01-24-2009, 09:12 PM

It sounds like your carb throttle shaft is hanging up and not returning to idle position, when you relieve the load on the engine. Take a look at your throttle return spring and see if it is not too weak, or maybe the carb has worn bushings in it and the shft is hanging up there.

1984Silverado4x4 · 01-25-2009, 09:50 AM

Ill take a look and see about both of those

Thanks guys

01-24-2009, 02:44 PM	#1
1984Silverado4x4 Registered User Join Date: Jul 2007 Location: Mount Horeb WI Posts: 179	Engine RPM's My truck has a 305 with the stock Quadrajet on it and a 4spd transmission. When I drive a vehicle with manual transmission I sort of expect the RPM to drop back to idle speed as soon as the clutch is disengaged. On my truck however when I disengage the clutch (depending on how fast im going, what gear im in, and engine temp) the engine will rev way up for a few seconds then settle down to idle. Couldnt tell you what it revs to as it dosent have a tach but I imagine 2500RPM or so. It happens the worst when the engine is cold and im only doing 25mph in 2nd gear and come to a stop sign or something. Anyone have ideas on why it would do this? __________________ Its no disgrace being poor. Its just inconvenient.

01-24-2009, 07:42 PM	#2
Restrorob The One And Only !!! Join Date: Jan 2007 Location: Hole in the woods Florida Posts: 4,567	Re: Engine RPM's It sounds to me that you could have a vacuum leak somewhere, Maybe a loose/cracked vac. hose or possibly intake ? __________________ 93 Jeep XJ 88 Buick La Sabra Toys; 88 TA-GTA in the works.... 97 GMC Ext. Cab 502 Crate 5 Spd......Sucks Gas But Haulz Azz ! The primary function of an Engineer is to make it difficult for the Fabricator and impossible for the Mechanic. *"Why go out preserved when you can go out beat up, worn out, sliding in sideways screaming, Holy Sh!t What A Ride" !!!* Last edited by Restrorob; 01-24-2009 at 07:43 PM.

01-24-2009, 09:12 PM	#3
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: Engine RPM's It sounds like your carb throttle shaft is hanging up and not returning to idle position, when you relieve the load on the engine. Take a look at your throttle return spring and see if it is not too weak, or maybe the carb has worn bushings in it and the shft is hanging up there.

01-25-2009, 09:50 AM	#4
1984Silverado4x4 Registered User Join Date: Jul 2007 Location: Mount Horeb WI Posts: 179	Re: Engine RPM's Ill take a look and see about both of those Thanks guys __________________ Its no disgrace being poor. Its just inconvenient.



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