Off idle stumble
Off idle stumble I'm helping a friend of mine tune his car. It's a 408, with a fairly large cam, and a th400. Long story short, if it's idling and you get into the gas at all, it will just stumble, or die, the rpm's won't raise at all. If you get into it 5-6% it's fine, but anymore than 10-20% it dies, or stumbles horribly. I have a log and the tune attached. The tune is very rough, we're just working on idle, and right off idle stuff. We're working with open headers, so we haven't had a chance to do any driving what so ever. Also does anyone know how to get the pcm to realize if it's in gear/not in gear with a TH400?
http://e-junky.net/Logandtune.zip
Any advice is appreciated.
Thanks guys,
Mike
http://e-junky.net/Logandtune.zip
Any advice is appreciated.
Thanks guys,
Mike
TECH Fanatic
Joined: Aug 2005
Posts: 1,691
Likes: 1
From: Sunny London, UK
Not sure about the TH400, maybe a manual tune rather than auto would help though.
As for idle, it sounds like a classic case of needing to tune in your running/desired airflow plus maybe follower
As for idle, it sounds like a classic case of needing to tune in your running/desired airflow plus maybe follower
On The Tree
Joined: Feb 2006
Posts: 156
Likes: 0
Originally Posted by Michael55123
I tried adding a few degrees of timing, but we got knock. Any other ideas?
Also what kind of plugs and what heat range/gap are you using?
Are you running in closed loop?
if so, do u notice it runs better while in open loop? (cold startup)
Trending Topics
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
Not if your EGR is disabled.
PM me with your email addy, I've got a change in your tune for you...
And with a T400 you'll have to run it as a manual tranny tune, or just change all your in-gear/neutral tables to be identical.
PM me with your email addy, I've got a change in your tune for you...
And with a T400 you'll have to run it as a manual tranny tune, or just change all your in-gear/neutral tables to be identical.
10 Second Club
Joined: Apr 2006
Posts: 62
Likes: 0
From: OFallon IL.
I understand my VE Tables aren't perfect yet my LTFT's and STFT's were not terrible. At least not enough to give me that kind of stumble. Also when the RPM's are brought up to avoid stumble it still acts lazy/unresponsive. Any thoughts?
first step is to get it running. It needs a little drive in order to calm down the LT's after a fresh flash. And you shouldn't even worry about ST's until you're LT's are between 5 to -5.
It's still no good how ya'll have less VE as MAP increases.
It's still no good how ya'll have less VE as MAP increases.
10 Second Club
Joined: Apr 2006
Posts: 62
Likes: 0
From: OFallon IL.
Cameron, I agree with you. I did use your spreedsheet to correct the VE curve and a difference was made. It still has a stumble but like you said maybe I just need more drive time to justify the changes and letthe fuel trims settle. As far as AFR the narrowbands were picking up low to mid 100's. LEAN.
I need to install my wideband I purchased a month ago and get some use out of it. As far as the stumble I've just been going off the narrowband as I know I'm lean. In fact I was watching a recent log and noticed a direct relationship between lean narrowband and knock. I guess I'll drive it more with Camerons VE and post up any change. Thanks again for all of your guys advise.
I need to install my wideband I purchased a month ago and get some use out of it. As far as the stumble I've just been going off the narrowband as I know I'm lean. In fact I was watching a recent log and noticed a direct relationship between lean narrowband and knock. I guess I'll drive it more with Camerons VE and post up any change. Thanks again for all of your guys advise.
