High idle after build
04-26-2010, 05:07 PM
#1
Launching!
Thread Starter
iTrader: (1)
Join Date: Jul 2009
Posts: 270
Likes: 0
Received 0 Likes
on
0 Posts
High idle after build Okay so heres the mod list: 5.3 2.5 heads, ported ls6 intake, 36# injectors, ms3 cam, pacesetter LT's, LM1 catback and y-pipe.
I installed all these things on my build and im sure there are some things im forgetting, but now (i know its utuned) it wants to idle at 2k rpms or higher in N or P but when i put it in gear it wants to die which is expected but wouldnt it want to die in Park too? If i leave my Intake Air Temp sensor plugged in the rmp's will just climb to redline and not come back down so i left that unpluged until i can hit a dyno... Also the car will run so sluggish for about a mile then just kick into high gear for about 100 feet or so then run like poo again, i know that cant be the cam doing that...
Any ideas will help, thanks! I hit the Dyno Wednesday
I installed all these things on my build and im sure there are some things im forgetting, but now (i know its utuned) it wants to idle at 2k rpms or higher in N or P but when i put it in gear it wants to die which is expected but wouldnt it want to die in Park too? If i leave my Intake Air Temp sensor plugged in the rmp's will just climb to redline and not come back down so i left that unpluged until i can hit a dyno... Also the car will run so sluggish for about a mile then just kick into high gear for about 100 feet or so then run like poo again, i know that cant be the cam doing that...
Any ideas will help, thanks! I hit the Dyno Wednesday
04-26-2010, 05:33 PM
#2
So your saying that you did a head/cam swap with bigger injectors with it being untuned and the idle being off? If the 36#ers are in and you aren't tuned for them put the stock injectors back in ASAP. You could be washing your cylinder walls, the stock computer won't know to correct for the injector without a tune. Gas in the oil pan sucks bro.
04-26-2010, 05:35 PM
#3
Launching!
Thread Starter
iTrader: (1)
Join Date: Jul 2009
Posts: 270
Likes: 0
Received 0 Likes
on
0 Posts
I thought the computer wouldnt allow it to let more fuel through the injectors without being tuned for more? I could be wrong but the computer shouldnt let more than the 28#'s through that the stock map was meant for?
04-26-2010, 05:54 PM
#4
TECH Resident
iTrader: (9)
Join Date: Oct 2005
Location: TEXAS
Posts: 989
Likes: 0
Received 0 Likes
on
0 Posts
Think about it this way, the PCM tells the injectors to open for X amount of time for any given situation. If, with your stock tune, at idle your 28lbs injectors are open for 5 milliseconds and flow 1oz of fuel and the idle is good. Now with the 36lbs injectors the PCM is still going to command an opening of 5 milliseconds at idle, but your 36ers are going to flow more during that time, say 1.5 oz of fuel, giving you poor idle. The PCM doesn't know that you installed larger injectors. So if i were you I would install the stockers untill you get a tune, also I wouldnt run it higher than 5k rpms because your injectors are more than likely above 80% duty cycle.
I just put random numbers above.
I just put random numbers above.
04-26-2010, 07:02 PM
#5
Think about it this way, the PCM tells the injectors to open for X amount of time for any given situation. If, with your stock tune, at idle your 28lbs injectors are open for 5 milliseconds and flow 1oz of fuel and the idle is good. Now with the 36lbs injectors the PCM is still going to command an opening of 5 milliseconds at idle, but your 36ers are going to flow more during that time, say 1.5 oz of fuel, giving you poor idle. The PCM doesn't know that you installed larger injectors. So if i were you I would install the stockers untill you get a tune, also I wouldnt run it higher than 5k rpms because your injectors are more than likely above 80% duty cycle.
I just put random numbers above.
I just put random numbers above.
04-26-2010, 07:51 PM
#6
Launching!
Thread Starter
iTrader: (1)
Join Date: Jul 2009
Posts: 270
Likes: 0
Received 0 Likes
on
0 Posts
Okay so i just put the stockers back in and i am still having high idle issues, and if i leave it in nuetral or park it wants to climb to about 3200 rpm's...
I have a slight knock now but since it wont idle i cant climb under it and see if it is the exhaust i just had welded to match my headers or if its an engine knock... (God i hope its not an engine knock!)
And when im cruising down the road it wants to sit at abotu 2100 rpm's so it will steadily climb in mph's.
I am kind of an ls1 noob and i built the motor so... i dont think i messed up but this is the first ls1 i built... lol
I have a slight knock now but since it wont idle i cant climb under it and see if it is the exhaust i just had welded to match my headers or if its an engine knock... (God i hope its not an engine knock!)
And when im cruising down the road it wants to sit at abotu 2100 rpm's so it will steadily climb in mph's.
I am kind of an ls1 noob and i built the motor so... i dont think i messed up but this is the first ls1 i built... lol
04-26-2010, 08:06 PM
#7
It sounds like you have a vacuum leak. When un-metered air is allowed into the intake, you get high idle.
I'd visually inspect the intake manifold and all lines connected to it, starting at the front of the engine (MAF to throttle body bellows). If nothing loose turns up, I'd pull the intake and ensure the gaskets are in place and no signs they are failing to seal against the heads' intake ports.
Also, what torque did you tighten the intake bolts to?
I'd visually inspect the intake manifold and all lines connected to it, starting at the front of the engine (MAF to throttle body bellows). If nothing loose turns up, I'd pull the intake and ensure the gaskets are in place and no signs they are failing to seal against the heads' intake ports.
Also, what torque did you tighten the intake bolts to?
Trending Topics
04-26-2010, 08:13 PM
#8
Launching!
Thread Starter
iTrader: (1)
Join Date: Jul 2009
Posts: 270
Likes: 0
Received 0 Likes
on
0 Posts
I checked all the vacuum lines and such asie from the one on the back just ow because its still kinda hot... i will check that one tomorrow though, i am fairly certain the gaskets are fine due to the fact that i checked them to be seated before i installed the intake... i torqued them in order first at 44 lbs then at 89 lbs i believe...
04-27-2010, 03:45 AM
#10
Also check your MAP sensor at the back of the intake can be a good culprit. If that isn't sealed that could be a possiblity. Did you get new intake runner gaskets or reuse your old ones? Reusing the old ones can cause bad seals also pending if they where the stockers.
I know it's simple but just throwing it out there, but the line from the intake to the brake booster. After my first cam install, almost missed it because I was so excited to start the car over for it's first cold start.
I know it's simple but just throwing it out there, but the line from the intake to the brake booster. After my first cam install, almost missed it because I was so excited to start the car over for it's first cold start.
04-27-2010, 05:51 AM
#11
I checked all the vacuum lines and such asie from the one on the back just ow because its still kinda hot... i will check that one tomorrow though, i am fairly certain the gaskets are fine due to the fact that i checked them to be seated before i installed the intake... i torqued them in order first at 44 lbs then at 89 lbs i believe...
A proper check, removing each line, inspecting it for cracks, and reinstalling it takes way longer than 7 minutes.
04-27-2010, 07:15 AM
#12
Teching In
iTrader: (3)
Join Date: May 2009
Location: Lakeland, FL
Posts: 43
Likes: 0
Received 0 Likes
on
0 Posts
I'd guess it's a vacum leak also. Remember that vacuum leaks can be found anywhere and not just in the hoses. Either that or you have left a sensor unplugged somewhere but the computer can usually compensate for that.
04-27-2010, 07:04 PM
#13
TECH Resident
iTrader: (9)
Join Date: Oct 2005
Location: TEXAS
Posts: 989
Likes: 0
Received 0 Likes
on
0 Posts
I checked all the vacuum lines and such asie from the one on the back just ow because its still kinda hot... i will check that one tomorrow though, i am fairly certain the gaskets are fine due to the fact that i checked them to be seated before i installed the intake... i torqued them in order first at 44 lbs then at 89 lbs i believe...
For the Relearn process I personally do this:
Unplug TPS and IAC valve connectors, take the idle set screw out of the TB and install it on top if you havn't already, start engine and see if you need more air to keep it running or vice versa, adjust idle set screw. Now you may have to start and restart your engine sevreal times to get it to idle right. Once the idle is good or better than before, its time to do the TPS relearn process. With the key in the off position, plug in your TPS and IAC connectors back in and turn the key to the run position and leave it there for 5-10 sec, turn it back to the off position. Now start the car and you should have a better idle quality for the time bieng, untill you can get a tune. Also there is a certian amount of adjustment that you can take too far(open the TB too much) I forget the TPS voltage maybe some one will chime in and help. It might be in the stickeys. Hope that helps.
Last edited by mcamarols1; 04-27-2010 at 07:12 PM.
04-27-2010, 07:36 PM
#14
Launching!
Thread Starter
iTrader: (1)
Join Date: Jul 2009
Posts: 270
Likes: 0
Received 0 Likes
on
0 Posts
I checked the lines before you posted... I'm sorry if it sounded different...
I called my tuner today after some ticking noise started to be heard quite loudly and he said to trailer it to the dyno tomorrow and he'd take care of it... So it's sitting in my shop over night til my dyno tomorrow... Wish me luck!
I called my tuner today after some ticking noise started to be heard quite loudly and he said to trailer it to the dyno tomorrow and he'd take care of it... So it's sitting in my shop over night til my dyno tomorrow... Wish me luck!
04-29-2010, 09:15 PM
#19
