Weird LTFT issue and maybe misfires? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

SQUEEGIO · 11-25-2018, 06:07 PM

So I just installed an ls9 cam in the car, other mods are catless LTs & CAI and 3.91s on an ls3. Car is tuned with an SCT x4 for everything but the ls9 cam. I have HPTuners on the way because I really want to get back I to doing my own tuning. I have basic experience with TunerCats in an LT1.

Anyways, I'm chasing my tail on an idle/slightly off idle stumble or misfire. Even when completely stock, my car always had the occasional stumble at idle but that seems to be normal from my experience with other ls3s. No CEL, new ACdelco plugs @.040 and Taylor 409 wires...misfire counters on scanner are all over the place on all cylinders but I guess not enough to set a code yet, they show up more at idle or if I hold the rpms steady around 1200 or so and you can definitely feel them as they show up on the scanner. Sprayed brake clean to check for vacuum leak on a cold engine but no obvious changes in rpm were noticed.

Now for the strange part... My LTFT at idle with the SCT x4 show 1.0 on both banks which is optimal.. STFT move around .96 to1.04 which is a 4% swing both ways from what I understand. Now with the car still running, I'll switch to my scanner and the LTFT are +6% both banks at idle. Why would the scanner and SCT show different values for LTFT? 2 different scanners show +%6 LTFT and the SCT shows no correction at all.

Also my mpg went down from about 16mpg city/some spirited driving, to now I have to try to get 13mpg with the cam and gears. I don't really care about mpgs just figured I'd throw that in here if it means anything.

I do have aftermarket header gaskets but don't seem to be leaking. I have gm ones on order just in case.
I really don't want to start tuning with fuel trims if there's a vacuum leak or these little misfires are going to skew my results.

Any suggestions? Thanks in advance!

Edit: wow sorry for the long post lol

Pro-tuned · 11-26-2018, 03:27 PM

Check grounds and 02 sensors.

SQUEEGIO · 11-26-2018, 09:25 PM

Is there some sort of diagram of all the grounds and where they are? I know from when I did the cam and lifters, there's one on the back of each head and one bigger one on the front of the pass. side head. I believe that's all the grounds I had to remove. I'll have to double check those when I get some time.

I remember the ones on the back of the heads we're tiny little ground wires..is there any way to install some beefier gauge wire or are those enough?

O2 sensor voltage swings up and down like it should. No CEL or codes at all.

Pro-tuned · 11-27-2018, 08:41 AM

Do a search someone posted pics of all the Ground locations (including battery connections), they should be clean and tight. Wiring can be internally corroded even with good ends. Put a multimeter on those wires check the resistance. LTFT steps in to help STFT when their limits are exceeded. Are your 02 sensors reading the same? If not change them from right to left and see if measurements go with them. I have seen misfires as a result of improper fuel adjustments. Vacume, exhaust, and timing. Just because your check engine light doesn’t come on means o2 sensors are ok... do you have a wideband?

SQUEEGIO · 11-27-2018, 09:34 AM

Found a schematic for the grounds so I'll check all of those. O2 sensors are oscillating about the same on both sides. I don't have a wideband yet but will in a couple months.

Also why is the SCT x4 reading different LTFT than the scanners?

I wouldn't doubt that my fueling/timing may be off because of the ls9 cam and not being tuned for it. But really don't think that's what's causing my misfires. If the cam is causing the + LTFT then I'm ok with it til receive my hptuners. If I'm remembering this correctly, even if the fuel trims are + or -, the whole point of having trims is to adjust back to stoich right?

Pro-tuned · 11-28-2018, 02:20 AM

LTFT inbalance can be the indicator of other issues. SCTX4 check to ensure you downloads are up to date, for the device and software’s. I have had issues with PIDs not working correctly before, I’m not surprised. You really need to run a log from HP tuners and get the wideband (lambda) and a FireWire and tap into the MVPI.

SQUEEGIO · 11-28-2018, 09:47 AM

Ok, hptuners will be delivered tomorrow. Only thing is it's the MPVI2 and as far as I know the only wideband that works with it right now is the AEM with obd2. Unless there's another way to get one to work.

I appreciate the help.

JANNETTYRACING · 11-28-2018, 11:42 AM

Quote:

Originally Posted by SQUEEGIO

So I just installed an ls9 cam in the car, other mods are catless LTs & CAI and 3.91s on an ls3. Car is tuned with an SCT x4 for everything but the ls9 cam. I have HPTuners on the way because I really want to get back I to doing my own tuning. I have basic experience with TunerCats in an LT1.

Anyways, I'm chasing my tail on an idle/slightly off idle stumble or misfire. Even when completely stock, my car always had the occasional stumble at idle but that seems to be normal from my experience with other ls3s. No CEL, new ACdelco plugs @.040 and Taylor 409 wires...misfire counters on scanner are all over the place on all cylinders but I guess not enough to set a code yet, they show up more at idle or if I hold the rpms steady around 1200 or so and you can definitely feel them as they show up on the scanner. Sprayed brake clean to check for vacuum leak on a cold engine but no obvious changes in rpm were noticed.

Now for the strange part... My LTFT at idle with the SCT x4 show 1.0 on both banks which is optimal.. STFT move around .96 to1.04 which is a 4% swing both ways from what I understand. Now with the car still running, I'll switch to my scanner and the LTFT are +6% both banks at idle. Why would the scanner and SCT show different values for LTFT? 2 different scanners show +%6 LTFT and the SCT shows no correction at all.

Also my mpg went down from about 16mpg city/some spirited driving, to now I have to try to get 13mpg with the cam and gears. I don't really care about mpgs just figured I'd throw that in here if it means anything.

I do have aftermarket header gaskets but don't seem to be leaking. I have gm ones on order just in case.
I really don't want to start tuning with fuel trims if there's a vacuum leak or these little misfires are going to skew my results.

Any suggestions? Thanks in advance!

Edit: wow sorry for the long post lol

It is unlikely you will see a perfect 1.0 so I suspect the PIDs you have selected are not working you could try selecting other LTFT PIDs and test.

The cam will cause your misfire counters to be more active.

+6 although is not Ideal is not far enough off to have a vacuum leak.

Obviously a change as big as a cam needs to be retuned.

You did have the option to purchase the SCT Protuner software for around 299.00 so you could still use your current SCT X4 tuner.

Ted.

Pro-tuned · 11-28-2018, 04:28 PM

Tuning with HP and understanding the complexity’s take time, experiences, a solid math background, creativity, and a lot of expertise. You could solve the issue rather quickly by logging and sending this to Ted. He is the primary tuner support for the club providing build packages and tuning. Ted is trustworthy and retains a very high international reputation.

With that said you will enjoy the depth of HP which allows you to be creative. Good luck!

SQUEEGIO · 11-28-2018, 05:56 PM

I did consider just paying for another email tune and I know that would be easy. Nothing against the tuners on here, I bought my SCT through Steve and have had an amazing experience with his customer service and his tune. I really do enjoy learning and don't mind if I don't have the best of the best tune in my car... The whole process of tuning it my self is rewarding enough.

Thanks for the pointers. I'll check all of my grounds this weekend, replace my header gaskets with GM ones and tripple check for vacuum leaks. Thanks again.

SQUEEGIO · 12-10-2018, 03:45 PM

Just a quick update for anyone who cares or comes across this in the future: No vacuum leaks found, I did find the ground on the front of the pass. head was not directly on the head.. it was in between two nuts in that bolt if that makes any sense. Fixed that but misfires didn't stop. Got to playing around with HPTuners and after learning about and adjusting my O2 sensor proportional and Integrator delay, misfires are almost completely gone. From what I've read lately, apparently these adjustments are sometimes necessary when installing long tubes due to the O2s being further away than stock. I've had the long tubes for a while but maybe adding the cam exaggerated the problem with the O2 location.

Also did a bunch of part throttle tuning and got my VVE and then MAF tables dialed in and car is running awesome! LTFT are in check now. Waiting to install my wideband to get working on WOT.

Thanks for the suggestions.

11-25-2018, 06:07 PM	#1
SQUEEGIO Drives: 2011 LS3 Camaro 2SS/RS Join Date: Aug 2015 Location: Colorado Posts: 32	Weird LTFT issue and maybe misfires? So I just installed an ls9 cam in the car, other mods are catless LTs & CAI and 3.91s on an ls3. Car is tuned with an SCT x4 for everything but the ls9 cam. I have HPTuners on the way because I really want to get back I to doing my own tuning. I have basic experience with TunerCats in an LT1. Anyways, I'm chasing my tail on an idle/slightly off idle stumble or misfire. Even when completely stock, my car always had the occasional stumble at idle but that seems to be normal from my experience with other ls3s. No CEL, new ACdelco plugs @.040 and Taylor 409 wires...misfire counters on scanner are all over the place on all cylinders but I guess not enough to set a code yet, they show up more at idle or if I hold the rpms steady around 1200 or so and you can definitely feel them as they show up on the scanner. Sprayed brake clean to check for vacuum leak on a cold engine but no obvious changes in rpm were noticed. Now for the strange part... My LTFT at idle with the SCT x4 show 1.0 on both banks which is optimal.. STFT move around .96 to1.04 which is a 4% swing both ways from what I understand. Now with the car still running, I'll switch to my scanner and the LTFT are +6% both banks at idle. Why would the scanner and SCT show different values for LTFT? 2 different scanners show +%6 LTFT and the SCT shows no correction at all. Also my mpg went down from about 16mpg city/some spirited driving, to now I have to try to get 13mpg with the cam and gears. I don't really care about mpgs just figured I'd throw that in here if it means anything. I do have aftermarket header gaskets but don't seem to be leaking. I have gm ones on order just in case. I really don't want to start tuning with fuel trims if there's a vacuum leak or these little misfires are going to skew my results. Any suggestions? Thanks in advance! Edit: wow sorry for the long post lol

11-26-2018, 03:27 PM	#2
Pro-tuned Angewendet Ingenieur Drives: 14 Camaro ZL1 Join Date: Apr 2015 Location: USA Posts: 401	Check grounds and 02 sensors. __________________ ———— LQ9, Iron Block, Forged internals, 408CI, Jannetty custom cam, TS short block, Whipple, Hardened Jackshaft, PRC 260, 2X3 Dynatech Full Competition, HF Cats, CAI, NW 103, Chee, ID 1300, COPO Breather, MSD, Fore Dual Pump, ultratorque, E85, dual Meth, True Trac, 3:45, 1500hp axle-shafts, DSS CF, BMR, custom Pearl/Candy paint by Jaidah.

11-27-2018, 08:41 AM	#4
Pro-tuned Angewendet Ingenieur Drives: 14 Camaro ZL1 Join Date: Apr 2015 Location: USA Posts: 401	Do a search someone posted pics of all the Ground locations (including battery connections), they should be clean and tight. Wiring can be internally corroded even with good ends. Put a multimeter on those wires check the resistance. LTFT steps in to help STFT when their limits are exceeded. Are your 02 sensors reading the same? If not change them from right to left and see if measurements go with them. I have seen misfires as a result of improper fuel adjustments. Vacume, exhaust, and timing. Just because your check engine light doesn’t come on means o2 sensors are ok... do you have a wideband? __________________ ———— LQ9, Iron Block, Forged internals, 408CI, Jannetty custom cam, TS short block, Whipple, Hardened Jackshaft, PRC 260, 2X3 Dynatech Full Competition, HF Cats, CAI, NW 103, Chee, ID 1300, COPO Breather, MSD, Fore Dual Pump, ultratorque, E85, dual Meth, True Trac, 3:45, 1500hp axle-shafts, DSS CF, BMR, custom Pearl/Candy paint by Jaidah. Last edited by Pro-tuned; 11-27-2018 at 08:55 AM.

11-27-2018, 09:34 AM	#5
SQUEEGIO Drives: 2011 LS3 Camaro 2SS/RS Join Date: Aug 2015 Location: Colorado Posts: 32	Found a schematic for the grounds so I'll check all of those. O2 sensors are oscillating about the same on both sides. I don't have a wideband yet but will in a couple months. Also why is the SCT x4 reading different LTFT than the scanners? I wouldn't doubt that my fueling/timing may be off because of the ls9 cam and not being tuned for it. But really don't think that's what's causing my misfires. If the cam is causing the + LTFT then I'm ok with it til receive my hptuners. If I'm remembering this correctly, even if the fuel trims are + or -, the whole point of having trims is to adjust back to stoich right? Last edited by SQUEEGIO; 11-27-2018 at 01:21 PM.

11-28-2018, 02:20 AM	#6
Pro-tuned Angewendet Ingenieur Drives: 14 Camaro ZL1 Join Date: Apr 2015 Location: USA Posts: 401	LTFT inbalance can be the indicator of other issues. SCTX4 check to ensure you downloads are up to date, for the device and software’s. I have had issues with PIDs not working correctly before, I’m not surprised. You really need to run a log from HP tuners and get the wideband (lambda) and a FireWire and tap into the MVPI. __________________ ———— LQ9, Iron Block, Forged internals, 408CI, Jannetty custom cam, TS short block, Whipple, Hardened Jackshaft, PRC 260, 2X3 Dynatech Full Competition, HF Cats, CAI, NW 103, Chee, ID 1300, COPO Breather, MSD, Fore Dual Pump, ultratorque, E85, dual Meth, True Trac, 3:45, 1500hp axle-shafts, DSS CF, BMR, custom Pearl/Candy paint by Jaidah.

11-26-2018, 09:25 PM	#3
SQUEEGIO Drives: 2011 LS3 Camaro 2SS/RS Join Date: Aug 2015 Location: Colorado Posts: 32	Is there some sort of diagram of all the grounds and where they are? I know from when I did the cam and lifters, there's one on the back of each head and one bigger one on the front of the pass. side head. I believe that's all the grounds I had to remove. I'll have to double check those when I get some time. I remember the ones on the back of the heads we're tiny little ground wires..is there any way to install some beefier gauge wire or are those enough? O2 sensor voltage swings up and down like it should. No CEL or codes at all.

11-28-2018, 09:47 AM	#7
SQUEEGIO Drives: 2011 LS3 Camaro 2SS/RS Join Date: Aug 2015 Location: Colorado Posts: 32	Ok, hptuners will be delivered tomorrow. Only thing is it's the MPVI2 and as far as I know the only wideband that works with it right now is the AEM with obd2. Unless there's another way to get one to work. I appreciate the help.

11-28-2018, 04:28 PM	#9
Pro-tuned Angewendet Ingenieur Drives: 14 Camaro ZL1 Join Date: Apr 2015 Location: USA Posts: 401	Tuning with HP and understanding the complexity’s take time, experiences, a solid math background, creativity, and a lot of expertise. You could solve the issue rather quickly by logging and sending this to Ted. He is the primary tuner support for the club providing build packages and tuning. Ted is trustworthy and retains a very high international reputation. With that said you will enjoy the depth of HP which allows you to be creative. Good luck!

11-28-2018, 05:56 PM	#10
SQUEEGIO Drives: 2011 LS3 Camaro 2SS/RS Join Date: Aug 2015 Location: Colorado Posts: 32	I did consider just paying for another email tune and I know that would be easy. Nothing against the tuners on here, I bought my SCT through Steve and have had an amazing experience with his customer service and his tune. I really do enjoy learning and don't mind if I don't have the best of the best tune in my car... The whole process of tuning it my self is rewarding enough. Thanks for the pointers. I'll check all of my grounds this weekend, replace my header gaskets with GM ones and tripple check for vacuum leaks. Thanks again.

12-10-2018, 03:45 PM	#11
SQUEEGIO Drives: 2011 LS3 Camaro 2SS/RS Join Date: Aug 2015 Location: Colorado Posts: 32	Just a quick update for anyone who cares or comes across this in the future: No vacuum leaks found, I did find the ground on the front of the pass. head was not directly on the head.. it was in between two nuts in that bolt if that makes any sense. Fixed that but misfires didn't stop. Got to playing around with HPTuners and after learning about and adjusting my O2 sensor proportional and Integrator delay, misfires are almost completely gone. From what I've read lately, apparently these adjustments are sometimes necessary when installing long tubes due to the O2s being further away than stock. I've had the long tubes for a while but maybe adding the cam exaggerated the problem with the O2 location. Also did a bunch of part throttle tuning and got my VVE and then MAF tables dialed in and car is running awesome! LTFT are in check now. Waiting to install my wideband to get working on WOT. Thanks for the suggestions.