Lterms at 25% at idle
Lterms at 25% at idle Alright i give up, my Lterms are at 25% at idle on both sides. I've taken the intake off, check the injector seals, and all the vacuum hoses. What's next, what do i need to look for. What kinda vacuum do LS1's pull? I've got a 230/288 .609/.566 112lsa cam. With stock heads and a LS6 intake. Stock MAF, and ported TB, idle is about 850 to 800 RPM's. This is in a M6 car. I've tryed carb cleaner can't find any vacuum leaks. What's the best way to find a leaks and am i over looking something? I avg. my Lterms at part gas and there around 0%. But when i let off the gas and go back to idle they go back to 25%. If you any of you have any idea's that would be great.
TECH Junkie
Joined: Nov 2001
Posts: 3,029
Likes: 0
From: Chi-Town
Re: Lterms at 25% at idle light a cigarette or something else smokey and move it around areas that might have a leak...obviously before the fans turn on. i found my leak was on the driveside vavle cover- on the pcv tube thingie.
On The Tree
Joined: Jan 2003
Posts: 172
Likes: 0
From: Central MD
Re: Lterms at 25% at idle idle=lean
EVAP system leak
Manifold vacuum leak
lack of fuel supply (low fuel pressure)
Exhaust leak before or within 18 inches after O2's (open headers)
Have you set any DTC's?
Log some data, like MAP, fuel pressure, MAF, TPS (TB stuck open?), KR and misfire(cam and LT's?). Evap should self test.
Just some ideas.
EVAP system leak
Manifold vacuum leak
lack of fuel supply (low fuel pressure)
Exhaust leak before or within 18 inches after O2's (open headers)
Have you set any DTC's?
Log some data, like MAP, fuel pressure, MAF, TPS (TB stuck open?), KR and misfire(cam and LT's?). Evap should self test.
Just some ideas.
On The Tree
Joined: Jan 2003
Posts: 172
Likes: 0
From: Central MD
Re: Lterms at 25% at idle Have you driven this car around since the install? Have you done anything to make it idle at higher rpm's?
Interesting cam numbers, where did you get it?
<small>[ February 17, 2003, 11:49 AM: Message edited by: 2000WhiteZ28 ]</small>
Interesting cam numbers, where did you get it?
<small>[ February 17, 2003, 11:49 AM: Message edited by: 2000WhiteZ28 ]</small>
Teching In
Joined: Apr 2002
Posts: 33
Likes: 0
From: Blue Springs, MO (KC suburb)
Re: Lterms at 25% at idle I have a blower and I was concerned about the crankcase being pressurized.
If the PCV is still stock there might be an obstruction or something causing it not to work correctly. Unplug the PCV connection into the manifold (just behind the throttle body on the passenger side) and let it suck air. Watch the fuel trims and if they start dropping you have located the problem.
If the PCV is still stock there might be an obstruction or something causing it not to work correctly. Unplug the PCV connection into the manifold (just behind the throttle body on the passenger side) and let it suck air. Watch the fuel trims and if they start dropping you have located the problem.
Trending Topics
Re: Lterms at 25% at idle Ok thanks for the help guys. I'll give some of that stuff a try. I do have a none stock PCV system. I've got the LS6 valley cover with a catch can. I looked around the headers where the O2's go in didn't see any leaking. Also put my rear O2's up front, didn't do anything. I'll keep you guys updated.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Re: Lterms at 25% at idle You might check you EGR too if you have one as a source of a Vacc leak. I've never heard of the STFTs being that high. Their limit is supposed to be +/-5% which sends the LTFTs moving to try to get the STFT back closer to 0. You MUST have a DTC set if your STFTs are at 25% because that's OFF THE SCALE. You should check your DTC to see if you can get some help on diagnosing your problem.
Re: Lterms at 25% at idle Well tryed the smoke deal didn't find anything. Tryed bypassing my catch can and using a stock LS6 pcv system and that didn't work. Also tryed to run it with the oil fill cap off, didn't do anything. I know the computer is just dumping fuel in you can smell it at idle. Map is at about 15.4 to 15.5. No KR, TPS at zero at idle.
TECH Resident
Joined: Jan 2002
Posts: 754
Likes: 0
From: USA
Re: Lterms at 25% at idle </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by QuickSilverTA:
<strong> Stock MAF, and ported TB, idle is about 850 to 800 RPM's. This is in a M6 car. I've tryed carb cleaner can't find any vacuum leaks. If you any of you have any idea's that would be great. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Go back to stock TB and restest.
Most times then not ported TB is the cause and is not needed anyways for a NA engine for stock TB and MAF was designed to handle up to 550 RWHP.
<strong> Stock MAF, and ported TB, idle is about 850 to 800 RPM's. This is in a M6 car. I've tryed carb cleaner can't find any vacuum leaks. If you any of you have any idea's that would be great. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Go back to stock TB and restest.
Most times then not ported TB is the cause and is not needed anyways for a NA engine for stock TB and MAF was designed to handle up to 550 RWHP.
Teching In
Joined: Apr 2002
Posts: 33
Likes: 0
From: Blue Springs, MO (KC suburb)
Re: Lterms at 25% at idle I know this is going to sound weird and illogical but I had the exact same problem. I had installed a Krank Vent PCV valve which gives a very positive shut off. At idle it was closed and my STFT was anywhere from +30 to +35 on both sides. My LTFT maxed out at +25. When I reinstalled the stock PCV valve the fuel trims dropped back to -1 to -3. For experimental purposes I reinstalled the Krank Vent PCV and trims jumped up again. I removed it without installing the stock PCV and they dropped.
The only explanation I have is the stock PCV is designed to leak through at idle and it wasn't. I know that doens't make sense because numbers on the plus side are lean and when I remove the PCV I am letting more "unmetered" air into the system. What I do know is that it worked.
The only explanation I have is the stock PCV is designed to leak through at idle and it wasn't. I know that doens't make sense because numbers on the plus side are lean and when I remove the PCV I am letting more "unmetered" air into the system. What I do know is that it worked.
