can high ltfts cause knock durring wot ?

**shady milkman** · 09-13-2010, 11:53 AM

can high ltfts cause knock durring wot ? logging my car i notice my bank 1 ltft and stft read higher and more active than my bank 2...and when i got wot i record up to 4 degrees of knock retardation ..could the possible exhaust leak be causing my ltfts to get scewed and retard timing durring wot ?

also my ltft sit at 25 quite a bit ...reason for concern ?

**Frost** · 09-13-2010, 11:58 AM

YES large cause for concern!!

the exhaust leak (frash air that makes it's way to your O2 sensor) makes the PCM 'think' the car is lean and it will DROWN one side of the engine in fuel.

**shady milkman** · 09-13-2010, 12:23 PM

Originally Posted by Frost

YES large cause for concern!!

the exhaust leak (frash air that makes it's way to your O2 sensor) makes the PCM 'think' the car is lean and it will DROWN one side of the engine in fuel.

ok that is what i thought...but since both ltft go 25 during light throttle or medium throttle but drops to like 15 during wot ..do i assume that there is a intake leak..since both banks are maxed..or just go after the one side that constantly reads higher when both arent maxed ?

sorry..i am still green with this...i understanding the logging and such..just not where to go with the info the logs give me

**Mr. Luos** · 09-13-2010, 01:03 PM

With what little I know about the LTFT's.....
You want them at zero.
25% adjustment is HUGE and as Frost mentioned....cause for concern.

**shady milkman** · 09-13-2010, 01:07 PM

so basically it is safe to say i have a vacuum leak somewhere ...i am sure my tune isn't way off as it is frost's tune..oh well start with what i kinda know...more than likely i have a exhaust leak at the collector on the driver side..fix that and clear the ltft and re-log and go from there...am i right ?

**Mr. Luos** · 09-13-2010, 01:13 PM

Pretty much.
Easy enough to check for vacuum leaks....carb cleaner around the base of the intake and whatnot.

**shady milkman** · 09-13-2010, 01:15 PM

Originally Posted by Mr. Luos

Pretty much.
Easy enough to check for vacuum leaks....carb cleaner around the base of the intake and whatnot.

think maf cleaner will work ?

**Mr. Luos** · 09-13-2010, 01:17 PM

Sure it would be fine....
Just make sure it can combust easily.

**Frost** · 09-13-2010, 01:40 PM

Misfires 'look' lean to the PCM as well (unburned cylinder charge) and will cause the fueling to wander off positive.

**shady milkman** · 09-13-2010, 02:46 PM

Originally Posted by Frost

Misfires 'look' lean to the PCM as well (unburned cylinder charge) and will cause the fueling to wander off positive.

i thought about that at first and logged it....i logged misfires for each cylinder and none showed up for either....

all i need to log misfires is to add under the engine diagnostics for "misfire current cylinder #X" correct ?

**Cutlass** · 09-13-2010, 06:50 PM

this sounds familiar. Haven't you been plagued with running lean/ vacuum leaks in the past? I seem to remember you had some problems with your LS6 intake or something. Wasn't it cracked or what?

**shady milkman** · 09-13-2010, 07:02 PM

Originally Posted by Cutlass

this sounds familiar. Haven't you been plagued with running lean/ vacuum leaks in the past? I seem to remember you had some problems with your LS6 intake or something. Wasn't it cracked or what?

yeah...used to idle and throw a bunch of codes...like system lean bank 1 and 2 and such...havent had those in a long time...if my ltfts and stft are so high...shouldn't i be throwing some type of code ?

**pajeff02** · 09-13-2010, 07:03 PM

Stock or aftermarket MAF?

**shady milkman** · 09-13-2010, 07:04 PM

even tho i have cleaned my maf and such..i wonder if my maf is not reading quite right ..or if my map is reading correct

**shady milkman** · 09-13-2010, 07:06 PM

Originally Posted by pajeff02

Stock or aftermarket MAF?

stocker...but it has over 100k on it and used to run a k&n filter...

**Cutlass** · 09-13-2010, 07:34 PM

Originally Posted by shady milkman

yeah...used to idle and throw a bunch of codes...like system lean bank 1 and 2 and such...havent had those in a long time...if my ltfts and stft are so high...shouldn't i be throwing some type of code ?

I would certainly think so

**0rion** · 09-13-2010, 08:02 PM

where is your exhaust leaking at? If it's before the front O2's I would get that fixed before going any further.

**Frost** · 09-13-2010, 08:56 PM

Shady, email me a log. Include some WOT as well. I can tell you if the MAF is reporting low.

**shady milkman** · 09-14-2010, 05:36 PM

log 2

log 3

**shady milkman** · 10-04-2010, 02:11 PM

ok a update... i took off my driver side header...saw no leak..and the gasket looked good..so bolted it back up and then took my intake manifold off. There was a small leak in the back of the intake. so i JB welded that shit up ..but what concerned me was when i took my fuel rail off..my #7 injector was dripping fuel..i assume this is not normal..so now i need to address this issue to (maybe)