Engine revs up when starting - The 1947 - Present Chevrolet & GMC Truck Message Board Network

aknovaman · 05-31-2015, 08:43 PM

Tune air flow startup tables are not correct for your engine and need adjusted. Another possibility is you have a vacuum leak that the initial startup opens the iac then closes it to compensate for the added air from the vacuum leak to bring the rpm down to the commanded idle speed.

johnyoung · 05-31-2015, 09:21 PM

Thanks for the help. I will check that out tomorrow. I need to show some pictures of our install as it is really nice and clean. Looks like it came in there from the factory. Anyone else have any ides just put her on here. I appreciate the forum as it's everybody helping out. One person here told me Chevy had problems with the 08,09 model motors with PCV valve and another guy said EGR valve. Motor sat since 09 until started about 4 weeks ago.

**dayj1** · 05-31-2015, 09:52 PM

Quote:

Originally Posted by johnyoung

Thanks for the help. I will check that out tomorrow. I need to show some pictures of our install as it is really nice and clean. Looks like it came in there from the factory. Anyone else have any ides just put her on here. I appreciate the forum as it's everybody helping out. One person here told me Chevy had problems with the 08,09 model motors with PCV valve and another guy said EGR valve. Motor sat since 09 until started about 4 weeks ago.

'08 and '09 shouldn't have a PCV valve. Somewhere around 2003/2004 GM went to a fixed orifice that is cast into the truck valve cover. An '09 shouldn't have an EGR valve either. That went away on the truck motors in 2002. You also don't have an IAC valve since that is only for DBC setups and your Gen IV motor should be DBW. The vacuum leak theory is a good one and that's what I'd be looking for.

solidaxel · 05-31-2015, 10:42 PM

Quote:

Originally Posted by dayj1

'08 and '09 shouldn't have a PCV valve. Somewhere around 2003/2004 GM went to a fixed orifice that is cast into the truck valve cover. An '09 shouldn't have an EGR valve either. That went away on the truck motors in 2002. You also don't have an IAC valve since that is only for DBC setups and your Gen IV motor should be DBW. The vacuum leak theory is a good one and that's what I'd be looking for.

Thanks for the information on the PCV system on my engine!
I have been wanting to ask the question on PCV"s

05-31-2015, 08:43 PM	#1
aknovaman Registered User Join Date: Aug 2013 Location: Tecumseh Posts: 355	Re: Engine revs up when starting Tune air flow startup tables are not correct for your engine and need adjusted. Another possibility is you have a vacuum leak that the initial startup opens the iac then closes it to compensate for the added air from the vacuum leak to bring the rpm down to the commanded idle speed. __________________ Current project 1959 Willys = GEZR TRUK Geezer is a Latin compound word made up of two roots. Gee meaning Urine Stain and Zer meaning your pants are open! FMCDH GBU and GBA http://www.youtube.com/user/aknovaman/videos

05-31-2015, 09:21 PM	#2
johnyoung Registered User Join Date: May 2010 Location: London, Kentucky Posts: 88	Re: Engine revs up when starting Thanks for the help. I will check that out tomorrow. I need to show some pictures of our install as it is really nice and clean. Looks like it came in there from the factory. Anyone else have any ides just put her on here. I appreciate the forum as it's everybody helping out. One person here told me Chevy had problems with the 08,09 model motors with PCV valve and another guy said EGR valve. Motor sat since 09 until started about 4 weeks ago.



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