Old time member here, but haven't posted in many years. Currently own two Gen 6 SS models. The 2001 (and) 2003 Jeff Gordon series are both normally aspirated 3.8L. I've had incredible service from both. Their only weakness is the plastic intake manifolds. Three manifolds have been replaced between the two cars. The 03 blue Jeffy has 150,000 and the 01 has 373,000 miles and still runs excellent and has been my daily driver for the past 17 years since I bought it. Both engines are original. I am currently looking to buy another Monte Carlo but have my share of reservations about buying a used 2006/2007 Gen 7 that has the 5.3L V8.

I've done allot of investigating and reading to learn the 5.3L reputation, but it can be rather confusing because some of the issues and problems that articles discuss, don't always do a good job at clarifying exactly what generation 5.3L the specific failures apply. The 5.3L was first introduced in 1999 to current, but has just been dropped from the Silverado after 2022. Throughout this span there have been three distinct generations of this engine (and) a slew of LC/LS variations within each generation. Even repair centers tend to speak too generically when I ask questions about this engine reputation. Keeping up with it all is mind boggling even for the professionals. But for the purpose of this public inquiry, I'm focussing on the LS4 used in our beloved Monte Carlo SS in 06 and 07.

Here's some LS4 stats so we're all clear...
Vortec 5300
Production from 2005-2009
GM's 4th generation small block V8
Used in Monte Carlo SS, Impala SS, Buick LaCrosse Super and Pontiac Gran Prix GPX
First generation of the 5.3L to possess AFM -Active Fuel Management for cylinder deactivation
The only transverse 5300 / with V6 bell housing
Aluminum engine block
Aluminum cylinder heads
Plastic Intake Manifold

In my studies, the five biggest 5.3L flaws that seem to include the LS4 variant are:
1. Excessive oil consumption
2. Excessive spark plug fouling
3. Excessive internal carbon buildup
4. Plastic Intake Manifold / sealing failures
5. Cracked cylinder heads

Items 1 & 2, the excessive oil use and spark plug fouling are related issues - caused by the Active Fuel Management (AFM) design - causing oil to be drawn out of the valve train through the PCV valve, where it gets sucked into the intake. The other AFM problem, causing oil burning, is due to a faulty oil pressure relief valve that sprays oil directly onto the piston skirt causing the rings to become overloaded and oil finding its way into the combustion chamber. Owners have also experienced their oil life monitoring system to not notify properly. GM issued a Service Bulletin for these problems, but it supposedly does not mention Monte Carlo. The TSB outlines the fact that the valve cover design on engines built before February 1st, 2011, has a poorly designed PCV pullover that will draw oil out of the valve train and into the intake manifold and combustion chambers. I have watched YouTube videos of repair centers saying there is an updated valve cover design that relocates the PCV valve further to the front, helping prevent part of this problem. There is supposedly no fix for the oil pressure relief valves spraying oil on the piston skirts - it is an inherent design flaw.

Item 4 is an old issue we've all dealt with on our 3.8L V6's for decades, myself included. I was very disappointed to learn GM still uses this junky plastic design on the 5.3L V8.

Item 5 Cylinder heads. While this issue was not common enough to warrant a recall, GM did issue a technical service bulletin (TSB) about the problem. The issue stems from a manufacturing flaw when the cylinder heads were produced by an outsourced company called Castech. Not all Castech heads have the issue, and not all Vortec 5300 engines have Castech heads, so determining if a vehicle has or may have this issue can be a bit difficult. It is unclear whether this problem was only restricted to the 3rd gen 5.3L (1999-2007), or if it found its way onto our 4th gen LS4 (2005-2009) Monte engines with AFM.

After numerous failed lawsuits, on October 3, 2022 a jury in a new GM class action lawsuit found General Motors liable for breach of warranty and other consumer protection claims in selling certain GM trucks and SUVs with the excessive oil consumption defect directly related to the Active Fuel Management design. They awarded 38,000 customers each $2,700 totalling $106.3 million in damages. But this lawsuit only covers a narrow sliver of AFM engines (and people) because it applies to the the 4th gen LC9 Vortec 5300 from 2011-2014 only - and furthermore only applies to buyers in California, North Carolina and Idaho. Often times, such lawsuits get improperly narrowed down to a far more limited subgroup than what it should, but it happens because of lawyer-eering and technicalities... so just because LS4 Monte Carlo owners weren't included, doesn't mean we're exempt from some of the issues.

So here's my dilemma and quandry folks... I did searches on this website using 5.3L and 5300 and found nothing meaningful on these issues. I would like owners of this 5.3L V8 LS4 Vortec engine to please post your comments and describe your satisfaction, disatisfaction AND service experience with it. If you own a 2006 (or) 2007 Monte Carlo SS, then you have this engine. It also doesn't matter if you have this engine in an Impala SS, Buick LaCrosse Super or the Pontiac Gran Prix GPX either... please provide feedback here. If you have friends, family or coworkers with this engine, take a moment and ask some details. If anyone would please be so kind to post these experiences I'd truly appreciate it. We all know the power and throaty sound of the Montes with these engines, so that's not what I want to know about... I'm looking for hardcare mechanical matters. I need to buy another Monte Carlo, but can't decide if the 5.3L AFM engine is a nightmare to run away from, or not. I'm old enough to remember the 1970's when GM really srewed up with the aluminum Chevy Vega / Pontiac Aster engine... and the disasterous failure of GM's first attempt at cylinder deactivation on their Cadillacs in the mid 70's... then there was the ridiculous junky Quad-4 in the 80's & 90's. Is this gen 4 Vortec 5300 LS4 just another modern example to avoid?

Please advise.

 

You've got a lot of points there to discuss, but I dont have time to talk to each one at the moment. I'll circle back in the next day or two to add more specific discussion.

The bottom line is that the issues you listed dont include the #1 failure point by far - the transmission. IMO the stock transmission was never strong enough, even for a stock LS4. Doesnt matter how much you beat on it or not, it will fail at a far higher rate than behind any other GM engine.

IMO I wouldnt buy a LS4 car unless it had proof of a built trans from triple edge or was so dirt cheap that you could afford to do that without exceeding the low value of the car. Thats really the biggest downside to them - you're either forced to spend 50%+ of the cars value to keep it together or you cross your fingers and never use the power in fear that it'll come apart one day (which is a really crumby spot to be in with supposedly the highest performance trim level of a given car).

 

This is unfortunately common with all DOD/ AFM LS engines, as are failed AFM lifters. Some people run forever with no issues, others end up with issues. You can disable it electronically, or if you're very paranoid about the potential for failure, you can delete the whole system (as anyone going to an aftermarket cam does).

I personally never had any issues, although I will say oil consumption was the highest of any vehicle I've ever owned - but never to the point of being alarmingly high (just under 1 quart per OCI). Not sure if that was the engine itself or related to AFM.


All LS engines get oil into the intake - not just 5.3 / AFM cars. Its a simple fix if you're worried about it though- just add a catch can in line with the pcv system.

I've always put catch cans on my LS cars (and my 3800 monte) to help keep the intake clean. Ive always had at least 4 ounces of oil caught (up to a max of about triple that) in the can at each oil change.

IMO just forget the monitoring system on any car and just go by mileage. I don't rely on that system for any car I own as some cars have reccomended absurdly long OCIs that I'm not comfortable with. I get that modern oils can hold up quite a long time (although there is plenty of evidence of sludging in localized spots despite that - IE older GM 3.6 engines), but I worry more about particles below the filters minimum size. Those particles continue to accumulate and circulate until drained out. I just dont think its worth saving a handful of $30 oil changes over the life of the vehicle trying to stretch them pit as far as possible.

The fix is simple - just add a catch can if it bothers you. Its really not a major issue - huge numbers of LS engines out there drink a bit of oil every day without issue.

Certainly there are people that have played with PCV pickup location, especially on hevaily modified engines, but on a stock LS a simple catch can is the cheapest way to address that.

TBH I've never heard of this before on LS4s, so I can't really comment on it. Maybe another LS4 owner on here has actually experienced it?

There's nothing wrong with plastic at all if used correctly. There are a huge number of LS engines out there, including some with absurd power and crazy high mileage with relatively few intake manifold issues. Sure there are occasionally failures of any part, but I wouldnt worry about LS plastic intakes being a main source of issues.

The 3800 intake problem is specific to 3800s - they pipe the hot EGR gases directly through it. This isn't done on LS engines.

If for some reason you're still worried about the LS4 intake, you can always swap it for something else (including metal if you're dead set on it). Its not as simple as a swap on regular RWD LS cars, but its not that major of a project either. But TBH people that swap to metal intakes tend to end up with more issues (as the ones on the middle/ low end tend to also be very low quality).

IMO, I've never heard of a 243 head cracking. I thought the Castech thing was only 706 and 862 heads? The LS4 never used those head #s.

If you're very worried about AFM issues, just delete it. IMO the fuel economy benefit isn't all that substantial anyways.

Personally, I'd just turn it off in the tune (because the exhaust sound is awful with it engaged) and drive it like that until something fails down the road.

Quote:

I would like owners of this 5.3L V8 LS4 Vortec engine to please post your comments and describe your satisfaction, disatisfaction AND service experience with it.

I owned a GP GXP for about 60k miles (from nearly new until it got rear ended / totalled). I loved the car, liked the engine, but the transmission is absolute garbage.

I had a few minor issues with the engine (failed water pump and rear main seals under warranty), but it was otherwise fine.

I will say I was a bit disappointed in the engine sound personally. I really wanted that V8 sound you hear out of a healthy Camaro / Vette, but its unfortunately nothing like that due to the single exhaust / manifold setup. It also sounds like a helicopter when AFM kicks in and shuts half the cylinders off. No doubt its worlds better than the 3800, just more truck sounding.

However I babied the transmission most of its life, and it was already giving me major issues when it got totalled. I was actually just getting ready to buy an aftermarket built unit (for most of the value of the car) when it got totalled, and was so happy I hadn't placed the order yet. Needless to say, I didn't buy another LS4 car. IMO thats the #1 reason their values are so low. They're the absolute pinnacle of the Wbody line (especially the GP GXP in terms of features), so they should've been the most valuable by far - yet people struggle to sell them because of that stigma that follows the cars around due to glass transmissions.

We actually had a local wbody club member scrap his whole car as a result of the transmission issues. He bought a SS Impala used, but the trans went out a few months into ownership. He assumed the car was abused and figured he'd pay a shop for a complete trans rebuild (which was near 100% of the value of the car pre-covid used car price craziness). Sure enough not even 2 years later and it broke again. Faced with the option of paying for a built trans this time (and being basically double the cars value into transmissions), he ended up parting the whole car out. Some other local Impala owners bought the interior pieces as an upgrade, and some Fiero guy bought the LS4. The rest of the car went to the scrap yard.

 

96 Monte... great points and great input. Deeply appreciate your time and experiences. I'll have a few followups to ask when I have more time too. I hit a deer with my oldest Monte and need to do some bumping & banging and put a used hood on today. What a way to spend New Years Day! In the meantime... everybody go find some LS4 5.3L owners and turn them upside down and shake them like a grizzly bear for some feedback. Let's see what kind of 5.3L service memories fall outta their heads!

 

Are the lifters that fail, tend to be for the cylinders that get deactivated, or are the lifter failures equally prone to the continuous cylinders too? I believe they are two different styles of lifters (correct?). How is the AFM/DoD disabled? Does it require the ECM to be connected to a scope and done through programming, or is there an external switch or method for laymen? If it's disabled, or deleted, does that mode interfere with future diagnostics when a service provider needs to scan the ECM for fault codes during routine service? Also, if disabled or deleted, is that an easily reversible process to reactivate or turn back on?

If that's the typical consumption rate, I don't consider that a real problem. Just a known characteristic to be conscious about. Articles I've read made it sound much worse.

Can you post a link for a typical catch can? I've never used one and would like to learn more.

Agree completely. I don't care about following the notification OCI either for my oil changes, however if the system isn't notifying, that's a deeper problem because the car generates this interval based in multiple pieces of information... ie crank revolutions, average oil temperature and other statistics monitored by the ECM. If the OCI notification isn't happening, then there's something else failing to provide necessary feedback... sensors? Signals? ECM calculations? ... the question would be what other vehicle systems are being adversely affected that also utilize the common inputs?

The articles I read made it sound semi-common. I have a friend with a 2018 Silverado using the 5.3L. His is in the dealership right now because of a related issue. The Oil Pressure relief valve needing replacement... the GM dealer says they've dealt with this numerous times... they claim its actually better to replace the oil pump and relief valve, both at the same time from past customer experiences... my friend is only a very short time out of warranty and now must pay $2,500 out of pocket on a truck with only 60,000 miles. He's furious. I realize his engine is the 3rd generation EcoTech and not our LS4, but it is an example of what the tech articles are talking about. I hope this problem doesn't trace back to the gen 2 LS4's also.

Thank you for this insight. It greatly expands my understanding into the 3800 UIM failure problem.

Again, please expound on this subject... exactly what is involved and how is it done?

 

It's the switchable lifters that can be problematic.

It can be turned off with an aftermarket tune electronically, but of course all of the components stay in place so that doesn't 100% prevent all potential issues.

It can be 100% removed by disabling it in the tune and replacing all of the associated components with non DOD parts. Several sites sell a DOD delete kit, and then you pick what cam to run (a stock grind or aftermarket).

The electronic disabling method is done via an aftermarket tuner.

No - but, if a dealer were working on the car in the future and did a re-flash to stock (say if a new tune was released via a TSB, even for a completely unrelated system), it would undo the aftermarket change. You'd either have to tell the dealer not to reflash it or let them do it and pay to get DOD turned back off by your aftermarket tuner afterwards.


Disabling it electronically is easily reversed. To undo a full delete is a pain as its taking all of the parts replaced in the conversion and putting them back to factory (including the camshaft). Its certainly possible, but its a good bit of labor.


I do want to stress that the whole thought of removing it completely is a bit over the top for someone not wanting to do an aftermarket cam already. If the car is running fine, I'd personally just drive it until an issue surfaces (if one does). GM has a TON of DOD engines out there now and the failure rate is nowhere near 100%. I only pointed it out that if DOD failures were thr biggest concern with buying one of these engines that it can be addressed completely if thats the main holdup.


Some definitely are. IIRC GMs official position was that anything OVER 1 qt in 2k miles was abnormal/ cause for warranty work, and there have been people beyond that. Luckily mine was never near that amount and never seemed to get worse throughout the time I had it.

https://www.eliteengineeringusa.com/...tte-2005-2013/

Typical is a tough term here. Theres a very wide variety of quality levels and designs. Essentially they're all just causing the air to make tight turns so that the oil vapor slings out of it and collects in some kind of reservoir. There are simple ones for $20 and higher end ones up in the hundreds.

Personally I use the type in the link above. Note that Im not saying this brand is the best or most cost effective, I just liked the clean look / quality fabrication (plus they had direct fit brackets for many of the cars I've put it on, unfortunately the LS4 isn't one of those), and it catches a good amount of oil on my LS and 3800 cars. Plenty of other options out there though.

If an error with a sensor key to engine operation occurred, you'd get a fault code. IMO there's nothing to worry about there. There could be tons of cars out there with oil reminder issues and the owners never know as so many people ignore it (either due to having a strict mileage schedule, or from ignoring maintenance in general).

Edit - I see there is TSB for the LS4 cars, #11-06-01-007

The hard part is trying to figure our what common really means (ie what % actually have the issue). If its the most likely issue to occur, but still only impacts a single digit percent of owners, then its probably not something to worry about. The hard part is trying to get a rough feel for what that % really is. Only suggestion I have there is to try keeping the research focused on LS4s specifically and browsing the most popular / common topics on their biggest forum. In the case of the LS4, I'd start in that specific section on the LS1tech board and try searching the different issues you mentioned to see how many hits you really get.



Just in general though, since you seem to drive a ton and appear to be very apprehensive about the LS4 cars), why not just stick with another 3800 car for the next go around? The 4t65 is a better match for that engine (especially the L36 variant) and the 3800 is a very reliable engine that you're already very familiar with. I know its harder to find them with lower mileage these days though.