MIL light on? Do you have a scanner? Thats going to be the best way to see what your engine is doing. You can get a bluetooth OBD2 scanner for cheap and get the torque app or some other scanner app on your phone. I would start trouble shooting there.

 

MIL light on? Do you have a scanner? Thats going to be the best way to see what your engine is doing. You can get a bluetooth OBD2 scanner for cheap and get the torque app or some other scanner app on your phone. I would start trouble shooting there.

 

If you figure this out, please let me know. Mine has never even gotten 14mpg and I can't find anything wrong with a scantool or OBD bluetooth scanner. 12-13mpg is about what I get on average and I'm not aggressive on the throttle. I was trying to diagnose this for a while but after several "fixes" I've kinda given up and surrendered to the thought of "I just have to pay to play". I've changed O2 sensors, MAF sensor, and put the air intake right behind headlight to get the coolest air temps possible.

I have thought about going to a dyno but it just seems silly to me to dyno tune a stock engine on a stock ECU in hopes of getting a few extra mpg. I figured that even if I managed to gain 50% more mpg, it would take me 2-3 years to recoop the dyno cost in fuel at the rate I drive my jeep.

 

If you figure this out, please let me know. Mine has never even gotten 14mpg and I can't find anything wrong with a scantool or OBD bluetooth scanner. 12-13mpg is about what I get on average and I'm not aggressive on the throttle. I was trying to diagnose this for a while but after several "fixes" I've kinda given up and surrendered to the thought of "I just have to pay to play". I've changed O2 sensors, MAF sensor, and put the air intake right behind headlight to get the coolest air temps possible.

I have thought about going to a dyno but it just seems silly to me to dyno tune a stock engine on a stock ECU in hopes of getting a few extra mpg. I figured that even if I managed to gain 50% more mpg, it would take me 2-3 years to recoop the dyno cost in fuel at the rate I drive my jeep.

Dyno isn't cheap, $500 but my fuel / air was way off, (stock tune) and since having it done, jeep runs alot better and now watching the MPGs . was able to fine tune the trans shifting too... was worth it...

23mpgs? i'm skeptical...

 

I have used my scan tool it never shows any problems. i put a diablo tuner on it didnt notice much of a difference. i have tried a a few things almost wondering if my Torque convert is not working properly, i did notice going in and out of 4L weather park or neutral it grinds like the trani is still in gear.

 

The transfer case doesn't have synchros so that's not that uncommon. As for gearing... Look at http://www.grimmjeeper.com/gears.html and figure out what your rpms should be at your given tire size and gear ratio. Don't be lazy... go measure your rear tires from the ground to the center of your axle. My 35" tires measure 17.75" from ground to axle center so when they're loaded, they are rotating as if it's a 33.5" tire. For the sake of diagnosis, you need that kind of accuracy. The difference between your 4L60E in a locked converter and unlocked converter is about 100-150rpms depending on speed and gear.

I just made this form so you can see and you really need a nice straight section of road and a bluetooth OBD readout or maybe your scan tool can give you that info so you can get a nice clean digital signal. This is the 4L60E and the charts on the left are a fully locked torque converter and the one on the left is a non-functioning or non-locked torque coverter. You may be able to use your scan tool to get information on the torque converter lock up signal as well but it depends on the capability. My scan tool doesn't directly tell me that the torque converter is locked but it will tell me the relative rpm difference between the input shaft and output shaft. If those two numbers are more than 0-2 rpms, I know my torque converter isn't locked.

 

according to the rpm site my tack is way off so either engine is running to fast or stock tach signal is different, I am guessing it is the latter.

 

LS engines run off a typical 4 cylinder tach signal. 2 pulses per revolution.

 

If you have a catalytic converter, it could be failing and restricting exhaust. Have you checked the air filter lately? Fuel blend can make a difference although 9 mpg is high. Have you confirmed that the odometer is measuring mileage accurately? Changed tire size or gears since last summer? Is the transmission still shifting into OD? Is the torque converter clutch locking?

Assuming you don't find any actual problems, a good next step might be to look at the data from the engine computer. There are a number of free apps that you can use with either a bluetooth OBDII reader or an OBDII cable. You can't adjust timing externally on an LS so after checking for codes you could watch the O2 sensor for proper activity, check for lean or rich operation, and check to see if the ecm is in Power Enrichment mode during regular driving. Depending on your ecm number there may be free software available that will allow you change the programming yourself. If you're not comfortable making the changes there are a number of tuners that can view data recorded while you drive to make changes to your calibration. Then you can use the free software and the OBDII connection to write the changes into the ecm. This process will take more time than driving to a tuner's shop and driving away with a completed vehicle, but it is likely to be cheaper.

 

So i have not tracked down the full problem yet but fuel injectors helped quite a bit next is coil packs. Apparently in the gen 3 ls motors the injectors are supose to be changed every 40k and mine are probably over 150k to 200k coil packs are supose to be done every 100k i had a tuner go threw it which brought me up to 16 city and 18 highway. Still waiting for a couple tanks of gas for computer to settle for the injectors. I will keep you informed.

 

I've never heard of that either but might not be a bad idea to refresh mine. My 5.3 likely has over 200k miles and I doubt any of that stuff was ever changed. Considering I was getting about 10 mpg last I looked, even getting 15 mpg would likely pay for itself in a year.

PS - I haven't verified my fuel economy since I got 38" tires because my speedometer won't go low enough to register the number of pulses given off by my sender.

 

That's interesting. I hadn't heard that the injectors were supposed to be changed that often. My motor has about 120k and the coil packs and injectors are stock.

Did you notice any power differences yet?

What size tires are you running?

 

Injectors every 40 K? seems excessive.... thats not a cheap replacement...

Edit: checked with my mechanic buddy, and he has a good friend who is a LS Tech and he is never heard of that

 

first question was about power and that is a hard one to answer i feel like is has more power after doing injectors but not much so i dont know if it is mostly wishfull thinking or not but i have noticed is shakes under load now which i believe is axle warp that i wasnt getting before. ladder bars or 4link here i come.



As for the injector swapping time line i have seen it several places an many different answers "We recommend cleaning fuel injectors at least every 36 months or 45,000 miles. Consider it a tune up for your fuel system- it's really amazing the difference people experience after having a fuel injection and throttle body cleaning on a car that has gone more than 60,000 miles without those services." So i figure mine has around 200k on it and i doubt they have ever been done it is probably time.


Waternut, I upgraded to a autometer programmable speedometer it would work with those tires.

 

first question was about power and that is a hard one to answer i feel like is has more power after doing injectors but not much so i dont know if it is mostly wishfull thinking or not but i have noticed is shakes under load now which i believe is axle warp that i wasnt getting before. ladder bars or 4link here i come.

As for the injector swapping time line i have seen it several places an many different answers "We recommend cleaning fuel injectors at least every 36 months or 45,000 miles. Consider it a tune up for your fuel system- it's really amazing the difference people experience after having a fuel injection and throttle body cleaning on a car that has gone more than 60,000 miles without those services." So i figure mine has around 200k on it and i doubt they have ever been done it is probably time.

Waternut, I upgraded to a autometer programmable speedometer it would work with those tires.

I'm still calling BS.... all the LS trucks / engines out there and I have never heard , nor seen them going in for injector "cleaning" . Just saying... If it was a thing, the dealers would be sending emails and letters like crazy for the service work... And I have owned multiple 5.3 -6.0 GMs

 

A fuel injector is the epitome of engineering and service-life testing. They are amazing!! or can be...

The only reason “service life” has gone down in recent years (or claims that it has gone have become more frequent) is to sell products and services. Imho

I don’t know the nozzle specs for an ls but I suppose that if the spray ports are smaller (potential for better atomization) on an ls more frequent service may be needed. But they can engineer in whatever they want to; fuel injectors are a matured product.

 

My FI's are 25 years old!!

 

I'm less concerned with injectors. I would think if 1-2 injectors were spraying funny, the fuel trims would be inconsistent. That and new injectors are stupid expensive. There are bucket loads of aftermarket injectors but reviews are 50% positive at best which doesn't inspire confidence in the quality.

I'm actually more concerned with coils. There seems to be a lot more debate as to when coils fail and how they fail. Some claim they go bad and you can feel them if you know what it's supposed to be but won't throw a code. Others claim that a single misfire will throw a code even when the coilpack is still good. I've also read a lot of things saying coils should be replaced between 100k-200k miles while some claim to fail at 50k and others claim over 300k on the originals. My LS engine does have a stutter at certain speeds that won't throw codes or anything useful but it definitely feels like a misfire. Feels like someone is tapping the brakes for a split second while driving some days. I have a scan tool that does live information but it doesn't log it and I will definitely get in a accident if I try to run 45-55mph in my Jeep while staring at multiple inputs on a screen.

 

I'm less concerned with injectors. I would think if 1-2 injectors were spraying funny, the fuel trims would be inconsistent. That and new injectors are stupid expensive. There are bucket loads of aftermarket injectors but reviews are 50% positive at best which doesn't inspire confidence in the quality.

I'm actually more concerned with coils. There seems to be a lot more debate as to when coils fail and how they fail. Some claim they go bad and you can feel them if you know what it's supposed to be but won't throw a code. Others claim that a single misfire will throw a code even when the coilpack is still good. I've also read a lot of things saying coils should be replaced between 100k-200k miles while some claim to fail at 50k and others claim over 300k on the originals. My LS engine does have a stutter at certain speeds that won't throw codes or anything useful but it definitely feels like a misfire. Feels like someone is tapping the brakes for a split second while driving some days. I have a scan tool that does live information but it doesn't log it and I will definitely get in a accident if I try to run 45-55mph in my Jeep while staring at multiple inputs on a screen.

I also get a misfire when i am sitting at a stop light and it is occasionally i dont have a fancy reader that can get into much detail just an obd2 code reader and it never logs it. what kind of reader/programmer would you recommend?

 

There is free LS tuning software available. LSDroid allows uploading and downloading of the vehicle calibration while Tunerpro allows one to log OBDII data and make changes to the calibration using a pc.


Injectors generally do not fail or wear out. It is possible for deposits to accumulate in and around the ports causing issues with atomization although most fuel today has sufficient detergent to prevent serious issues. I believe this is the source of recommendations to replace injectors at regular intervals.


The "half-assed misfire at idle" is a GM thing and it tends to be worse on engines with bore size 4" or larger. I believe it is due to cylinders not completely emptying of exhaust on the exhaust stroke. As the closed loop system drives fuel from rich to lean the combination of leaner mixture plus inert exhaust in the cylinder causes a misfire. In this condition you might feel a stumble or shake very briefly but it will quiclkly disappear as the ecm drives the mixture from lean back to rich. It can often be reduced with tuning by adjusting the lean limit richer and by setting stoich or the O2 crossing point to a slightly rich value.


When you are getting steady and regular misfire you should expect to check the ignition system, injector operation, and valve and cylinder head integrity. Our fleet vans tend to have a problem with valves even though we do not abuse them.

 

There is free LS tuning software available. LSDroid allows uploading and downloading of the vehicle calibration while Tunerpro allows one to log OBDII data and make changes to the calibration using a pc.

I can't find either of those apps in the google play store...

 

I'm actually more concerned with coils. There seems to be a lot more debate as to when coils fail and how they fail. Some claim they go bad and you can feel them if you know what it's supposed to be but won't throw a code. Others claim that a single misfire will throw a code even when the coilpack is still good. I've also read a lot of things saying coils should be replaced between 100k-200k miles while some claim to fail at 50k and others claim over 300k on the originals. My LS engine does have a stutter at certain speeds that won't throw codes or anything useful but it definitely feels like a misfire. Feels like someone is tapping the brakes for a split second while driving some days. I have a scan tool that does live information but it doesn't log it and I will definitely get in a accident if I try to run 45-55mph in my Jeep while staring at multiple inputs on a screen.

The computer is programmed to watch for changes in crank speed. It knows the crank should speed up each time the spark plug fires. If the crank does not speed up sufficiently it's counted as a misfire. Each misfire is added to a misfire counter. If the misfire counter increments quickly enough the ecm determines there is a problem. The ecm is programmed not to look for misfires under certain conditions such as a cold engine when the fuel is harder to light, or at idle in some vehicles, or possibly when A/C is active at low engine speeds. Because of these rules it is possible for misfire codes to occur when a coil is good and able to deliver enough spark. Insufficient combustion due to incorrect fuel delivery or low compression can be flagged as a misfire. OTOH it can be hard to make comparisons based on internet data if you don't have the complete story. If the vehicle is operated under conditions where the misfire counter is not incremented the ecm may never set a code. Or if the engine and calibration are from a heavy vehicle it may be programmed not to set individual cylinder misfire codes. It can be hard to know whaich data to filter out. Most GM vehicles will display misfire counter data but if not, there is a way using Mode $06 data if your reader allows it.

As a tech and a shop manager I can tell you from a customer service standpoint that most customers would rather not gamble on changing one coil on a vehicle with high mileage. The thinking is that if one coil failed the rest are close behind. I also know that most DIY guys are willing to save $$ and will replace only the coil they know is bad. I believe this is what leads to the range of recommendations found on the internet. In my experience Ford coils are more likely to fail in rapid succession than GM coils so we usually replace all Ford coils on a high mileage engine but replace a single failed coil on the LS family.

 

I can't find either of those apps in the google play store...

Thanks for letting me know. Next time I will include links. LSDroid is being developed independently. I know there is a dedicated webpage at http://ls-droid.com/ . There is also a facebook page and there are a number of users and a lot of discussion on gearhead-efi.com as well as other sites. You will need to sign up for an account to post or download on gearhead-efi. Tunerpro is a Windows based app. Tunerpro can be downloaded from https://www.tunerpro.net/ . It's technically a pay for app at $35 and it's well worth the $$ but the evaluation period never expires. I honestly don't know if it can be run in an emulator on Android but I do see folks talking about logging data with it on a phone or tablet. Definition files for the LS are also on gearhead-efi but may also be on other sites.

gearhead-efi link: http://www.gearhead-efi.com/Fuel-Injection/showthread.php?7676-Free-LS1-Tuning-Software-(all-you-need-is-TunerPro)

There are some videos about LSDroid on Youtube that might be interesting as well.
https://www.youtube.com/results?search_query=lsdroid

Full disclosure: I use a professional tuning package for my OBDII tuning so I have never used LSDroid. I have used Tunerpro for some OBDI tuning and for logging. It is a great tool.

 

so i was under the jeep last week and noticed some moisture around my high pressure fuel line next to the tank where the rubber hose goes into the steel next to the cross member it had a lot of dry rot and had been seeping fuel, was waiting for the weekend to replace it well the jeep decided it was not going to wait. went for a drive yesterday and was smelling fuel really bad pulled over and it was pouring out so got it back to the house dropped the tank and replace the line. finger crossed that I was loosing a gallon+ each tank.