Will installing a lower compression shortblock and smaller pulley cause codes?
Thread Starter
Wicked
Joined: Jul 2009
Posts: 675
Likes: 13
From: TN
Will installing a lower compression shortblock and smaller pulley cause codes?
So I have logged 85 miles on my new shortblock but Random/Multiple Cylinder Misfire code is being thrown. I am on the same tune from when it was a stock engine and 5" pulley. I now have an all forged shortblock, approx. 9.75:1 compression and went down to pulley sizes to 4.63". I also installed a Kenne Belle BAP. I am driving it like granny just to get some break in miles before I take it back to dyno for tune. I pulled all plugs, replaced them, verified spark plug wires are all good, and even flushed intercooler out to ensure it didnt have any oily buildup in it. It also sometimes shuts off completely when coming to a stop. I know I need to stay out of boost, and believe me, I am. But, will the change in compression and pulley size cause it to pull timing due to a lean condition, even at idle and light part throttle? Oh, it has been 100+ degrees and humid here in Savannah, GA.
Last edited by ANGRY Z; Jul 2, 2012 at 10:25 AM.
Melting Slicks
Joined: Feb 2006
Posts: 3,191
Likes: 43
From: Scottsdale Az
If you went from stock LS7 compression to the new numbers without a tune I would expect it to be funky.
It should have a "driveability" tune in it for the break in miles. Also have it logged to make sure the difference in tune is causing the issue and it's not something mechanical.
It should have a "driveability" tune in it for the break in miles. Also have it logged to make sure the difference in tune is causing the issue and it's not something mechanical.
Thread Starter
Wicked
Joined: Jul 2009
Posts: 675
Likes: 13
From: TN
Another note, possibly related to the shutting off, is that I dont have the driver's side 02 sensor plugged in at all. I unplugged and removed it so I could put my wideband in its place. The last tune may have not had the rear 02 sensors completely shut off. It pops the two codes for it immediately. Could this **** the computer off enough to shut it down?
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Thread Starter
Wicked
Joined: Jul 2009
Posts: 675
Likes: 13
From: TN
Another note, possibly related to the shutting off, is that I dont have the driver's side 02 sensor plugged in at all. I unplugged and removed it so I could put my wideband in its place. The last tune may have not had the rear 02 sensors completely shut off. It pops the two codes for it immediately. Could this **** the computer off enough to shut it down?
Melting Slicks
Joined: Feb 2006
Posts: 3,191
Likes: 43
From: Scottsdale Az
The misfire could be because of the drop in compression with timing/fuel being static, it may just not be firing off the mixture in the cylinder. Lower compression will require something to bring it back up to light off the same as before.
(Me thinking out loud with you since nobody else has replied)
(Me thinking out loud with you since nobody else has replied)
Racer
Joined: Jul 2011
Posts: 417
Likes: 0
Also just for gp have you checked to make sure all of your injectors electrical connectors are seated fully? I got that after installing my new fuel rails and it was a simple connector issue. Reseat them all, clear the codes then start it up and see if that fixes it.
Thread Starter
Wicked
Joined: Jul 2009
Posts: 675
Likes: 13
From: TN
The misfire could be because of the drop in compression with timing/fuel being static, it may just not be firing off the mixture in the cylinder. Lower compression will require something to bring it back up to light off the same as before.
(Me thinking out loud with you since nobody else has replied)
(Me thinking out loud with you since nobody else has replied)
Thread Starter
Wicked
Joined: Jul 2009
Posts: 675
Likes: 13
From: TN
Checked them and they are all good.
Thread Starter
Wicked
Joined: Jul 2009
Posts: 675
Likes: 13
From: TN
Burning Brakes
Joined: Nov 2005
Posts: 1,160
Likes: 3
From: Savannah GA
Sounds good man; hope everything turns out well. Are you driving it there to rack up the break-in miles? or are you trailering it? I know you need to stay off of boos, but not a biggie I guess when you are on the highway...
Thread Starter
Wicked
Joined: Jul 2009
Posts: 675
Likes: 13
From: TN
No trailer required. Driving it everyday, then down there for tune. It will have at least 400 miles on it by the time I drop it off. And it has already had 2 oil changes.