Head replacement - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


GMC/Chevrolet Truck/SUV When starting new posts, please specify YEAR, MAKE, MODEL, ENGINE type, and whatever modifications you have made.

Reply
 
 
 
Thread Tools Search this Thread
Old 05-23-2015, 08:03 PM   #1
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 3
Thanked 0 Times in 0 Posts
Mojica is on a distinguished road
Default Head replacement

I've changed heads on 99' vortec 5.7 fired it up noticed huge vac leak saw my booster line unplugged connect it and it died won't start now with or without vac line it was running around 1600 rpm for about ten mins before I plugged vac line in gauges were good scanner shows nothing from when it was running, I had two cracked heads and drove about five miles home so everything was working before head job it tries to fire but doesn't I've rotated the distributor every way but can't get it to start again
Mojica is offline   Reply With Quote
Old 05-24-2015, 07:39 AM   #2
Senior Administrator








Certified Car Nut
 
Mike's Avatar
 
Join Date: Jul 2003
Location: Horseheads, NY
Posts: 15,648
Thanked 1,000 Times in 776 Posts
Mike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond repute
Default

Hold the throttle open just a TAD. Now try and start it. If it starts and you let the throttle go, does it immediately die? If so, your IAC valve is closed all the way. This was because the PCM noticed the idle was very high due to the disconnected vac line and it tried to compensate by closing the IAC(Idle Air Control) valve.

Usually the IAC valve can be reset by turning power on for about 20 seconds and turning back off without cranking. Then power back on and proceed to crank. If this doesn't work, you may have to force it to relearn while driving around 35 MPH. This can take some double footwork to operate the brake and the throttle at the same time.
Mike is offline   Reply With Quote
The Following User Says Thank You to Mike For This Useful Post:
Mojica (05-24-2015)
Old 05-24-2015, 02:12 PM   #3
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 3
Thanked 0 Times in 0 Posts
Mojica is on a distinguished road
Default

Quote:
Originally Posted by Mike View Post
Hold the throttle open just a TAD. Now try and start it. If it starts and you let the throttle go, does it immediately die? If so, your IAC valve is closed all the way. This was because the PCM noticed the idle was very high due to the disconnected vac line and it tried to compensate by closing the IAC(Idle Air Control) valve.

Usually the IAC valve can be reset by turning power on for about 20 seconds and turning back off without cranking. Then power back on and proceed to crank. If this doesn't work, you may have to force it to relearn while driving around 35 MPH. This can take some double footwork to operate the brake and the throttle at the same time.


tried that, put crank back tdc took cap off timing still correct, poured gas directly into throttle body and kept it running a bit, now i did change fuel regulator because i blew a hole in bladder with air chuck now it seems fuel issue but it was running before head job
Mojica is offline   Reply With Quote
Old 05-24-2015, 02:49 PM   #4
Senior Administrator








Certified Car Nut
 
Mike's Avatar
 
Join Date: Jul 2003
Location: Horseheads, NY
Posts: 15,648
Thanked 1,000 Times in 776 Posts
Mike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond repute
Default

You do know you have a 25% chance of getting it right when you put the crank at TDC right? Best way in your situation with the 5.7, is to remove the left side(drivers side) valve cover. Rotate the engine by hand until you feel both #1 valve rockers feel loose. Both valves should be closed at this point. This is now TDC for #1. Now you can readjust your dizzy cap to point at #1 wire.
Mike is offline   Reply With Quote
Old 05-24-2015, 02:49 PM   #5
Senior Administrator








Certified Car Nut
 
Mike's Avatar
 
Join Date: Jul 2003
Location: Horseheads, NY
Posts: 15,648
Thanked 1,000 Times in 776 Posts
Mike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond repute
Default

The above also works the same for the little brother 4.3.
Mike is offline   Reply With Quote
The Following User Says Thank You to Mike For This Useful Post:
Mojica (05-24-2015)
Old 05-24-2015, 11:47 PM   #6
Junior Member
Thread Starter
 
Join Date: May 2015
Posts: 3
Thanked 0 Times in 0 Posts
Mojica is on a distinguished road
Default

thank you for your suggestions my timing is correct, pressure test my fuel pump apparently it decided to quit on me while I connected that vacuum line changed it out now adjusting valves in the morning
Mojica is offline   Reply With Quote
Old 05-25-2015, 07:29 AM   #7
Senior Administrator








Certified Car Nut
 
Mike's Avatar
 
Join Date: Jul 2003
Location: Horseheads, NY
Posts: 15,648
Thanked 1,000 Times in 776 Posts
Mike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond repute
Default

Well that was weird.
Mike is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Left head vs. right head? eazhar 1992-1999 3 04-09-2012 09:59 AM
455 Head Gasket Replacement wyckedcombo17 Classics (Star Chief and 1957 to 1986) 2 06-16-2010 02:18 PM
(warped head, new car hunt) head gasket on 88 voyager (2.5L) harofreak00 Lounge 47 02-01-2007 02:10 AM
Replacement Stock Head Unit Brian E. Audio (and aftermarket electronics) 1 10-04-2005 01:15 PM
Head-Light Turning Signals BonneAlien 1992-1999 10 10-28-2002 02:29 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 09:32 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.