LTFT's +20 at Idle . Possible Causses ?

[Indyblue98]

REPOST : From v8 Engine Bolt ons

Long Term Fuel Trims are reading +20 to +25 at idle (SCT TUNER )
Both Bank 1 and Bank 2 , But only at low rpm under 900

Driveabilty is good , and the LTFT's look good while driving.

Jannetty is providing tuning and wanted to see if there is a Vacuum leak .
Checked the easy stuff like Throttle Body and Catch Can.

Tried putting smoke around the edges of the intake .

Nothing obvious yet.

If there is a bad seal on one of the intake ports would that make both banks reading bad ?

Any ideas ?

Whipple has been on for a few hundred miles , new mods are the Long tubes/High flow cats.
No Data Logging till now, only 1900 miles now.
Now has CEL .

Mods: Whipple , Long Tubes W High Flow Cats , RotoFab . L99 Engine

[sting808]

Originally Posted by Indyblue98

REPOST : From v8 Engine Bolt ons

Long Term Fuel Trims are reading +20 to +25 at idle (SCT TUNER )
Both Bank 1 and Bank 2 , But only at low rpm under 900

Driveabilty is good , and the LTFT's look good while driving.

Jannetty is providing tuning and wanted to see if there is a Vacuum leak .
Checked the easy stuff like Throttle Body and Catch Can.

Tried putting smoke around the edges of the intake .

Nothing obvious yet.

If there is a bad seal on one of the intake ports would that make both banks reading bad ?

Any ideas ?

Whipple has been on for a few hundred miles , new mods are the Long tubes/High flow cats.
No Data Logging till now, problem may have been there since the car was new only 1900 miles now.

Mods: Whipple , Long Tubes W High Flow Cats , RotoFab . L99 Engine

Do you notice right after you come to a complete stop(0 mph), ltft holds the good trim, then slowly starts to drift and gets leaner as you idle? It does not occur when rolling, with clutch in or out of gear since rpm is above 900?

I just upgraded to Lion and need to reinstall hpt. Also, dl'd lastest 2.23beta. No exhaust leaks, cannot find vacuum leak. I do notice spikes in trim while driving and laying off throttle, but nothing like at idle with constant +20. I test tune has addressed the symptom, but haven't done enough logging since i upgraded failed hard drive and OS.

2010 LS3 w/kb 2.8 and LT.

[formare]

More common cause this difficult to find would be.......... Catch can drain valve open causing a vacuum leak. It's easy to do.

Wouldn't anything above +\- 20 cause a CEL?

[TriGun]

Check your MAF readings and wither you have strong MAF or not, also check if you have any exhaust leaks and check O2 sensors too. Did you installed the oem header gasket or not ?

[Indyblue98]

Actually just went out to do some more checking.. CEL is on.
But has not been the last few times I drove for data logging.

The car has a strong MAF .

Basic's are when the throttle is almost closed . below 6% and rpms under 1000.

When driving-acceleration the numbers are great .98-1.03

Checked the drain plug its ok.

Reused the OEM Gaskets. Don't think there is a leak from those.

Car is really quiet for having headers , still factory pipe past the cats.

[TriGun]

positive ltft value means the mixture is lean and the ecu is adding fuel.

so lean means either the engine getting more air our getting less fuel.

faulty o2 sensors, bad cats, major exhaust leaks, bad fuel injectors, bad fuel delivery all possible causes.

did you upload a tune that correspond to your mods ?

and don't worry, Ted@JRE is the man. He will fix it for you.

[sting808]

Originally Posted by Indyblue98

Actually just went out to do some more checking.. CEL is on.
But has not been the last few times I drove for data logging.

The car has a strong MAF .

Basic's are when the throttle is almost closed . below 6% and rpms under 1000.

When driving-acceleration the numbers are great .98-1.03

Checked the drain plug its ok.

Reused the OEM Gaskets. Don't think there is a leak from those.

Car is really quiet for having headers , still factory pipe past the cats.

Try logging, in a safe way, rolling, then stop, and see when the trims climb past +20 and send it to Ted. I caught mine when CEL triggered. My test tune is working, but have had time to log and drive around.

Have/had the same thing. Easy seal clamps on flanges, checked OE exhaust gasket area at LT flanges. Hi temp RTV around O2 and exhaust connections. Checked for vacuum leak. Good MAF sensor. Checked catch can system. Car runs good. Produces good power per setup. I know your pain...

[Indyblue98]

Originally Posted by TriGun

did you upload a tune that correspond to your mods ?

and don't worry, Ted@JRE is the man. He will fix it for you.

Tunes , yes, we are on the 4th generation

And I know Ted hasn't given up , but since we both work day shift it leaves me with evenings to log data and the next day he anayizes and gives suggestions.

My latest findings are : the Map sensor is a b#tch to get to , again, but at least it was properly installed a few days ago.

More improtant I took the Catch Can out of the circuit and the LTFTs dropped to 1.08 -1.11 range.
Thats just sitting in the garage.
Need to find the proper way to route hoses without the catch can and do a road test / log data again .

[LBV]

Need to get that CEL code first as it'll direct you to a likely source. Then again, the CEL could be because you've gone past the LTFT's limits before a code throws.

Mine at idle are 10 (can't recall if + or -).

[Padre]

Originally Posted by TriGun

positive ltft value means the mixture is lean and the ecu is adding fuel.

so lean means either the engine getting more air our getting less fuel.

It most likely means a leak in the headers, collector or cat seals.

Air is getting in downstream, causing the O2 sensors to read high (lean), so it's adding fuel.

So to IndyBlue: retighten everything.

Had it happen when I installed my cats, easy fix.

Padre

[Indyblue98]

Originally Posted by LBV

Need to get that CEL code first as it'll direct you to a likely source. Then again, the CEL could be because you've gone past the LTFT's limits before a code throws.

Mine at idle are 10 (can't recall if + or -).

I did a code description before clearing them off.
P0171
P0174
LFTT bank 1 and 2

So yeah the ECU is getting tired of the new high errors.