GM 2.7L L3B Engine Problems – But Wait, It’s Actually A Great Engine?

There are not a lot of 4-cylinder engines fitted to a full-size truck, or, at least there used to be none. However, times are changing and so are the engines. Things tend to get small and more advanced. V8 purists will cringe at the thought of having a relatively small 4-cylinder, turbo and direct injection engine fitted to a full-size pick-up truck like the Chevrolet Silverado or GMC Sierra. But here we are, GM introduced the 2.7 L 4-cylinder engine in 2019 and although it does have some issues (which we would call minor), GM did not have problems with selling them, they had problems keeping up with the demand. Today, we are focused on the GM 2.7L L3B Engine Problems.

The GM L3B engine, as it is known, features GM’s active fuel management (even in the 2022 model year), a start-stop system, variable valve timing and GM’s very own intake valve lift control. When you couple all of these features with a nice BorgWarner turbo, the horsepower is there, all 310-325 of them (depending on the model year).

Despite the fact that this engine was a laughing stock of the truck community, it actually proved itself to be a fairly reliable workhorse. Like all engines, it had some problems in its infancy but with each model year it did and it will get better. Here are the most common GM 2.7L L3B Engine Problems.

Known And Common GM 2.7L L3B Engine Problems And Complaints

We talk about direct-injection engine problems quite a lot here on LifeOnFour. And generally speaking, a large percentage of them suffer from the same issues; carbon buildup on the intake valves, fuel injector problems and fuel dilution. The GM 2.7L L3B Engine does suffer from some of those typical petrol direct injection problems. Here are all the known ​​GM 2.7L L3B Engine problems.

Engine Carbon Buildup

This is a typical problem of direct-injection engines that are not combined with a port injection fuel delivery system. The GM L3B’s fuel injectors disperse the fuel directly into the combustion chamber which in return produces more power, uses less fuel and emits less environmentally harmful emissions. All great things right? The downside to this is that as opposed to the port-injected engines, where fuel is sprayed into the intake manifold there is no natural cleaning effect of the intake manifold. This leads to an accumulation of carbon deposits which starts to cause serious problems down the road. The most common problems include a rough idle, poor acceleration and misfiring.

This problem started appearing as the first vehicles with this engine started reaching higher mileages. To learn what are the symptoms of engine carbon deposits, make sure you read our article on that exact problem.

Fuel injector problems

The GM 2.7L L3B engine has now spent enough time in the hands of first buyers in early 2019 that we can get a good feeling of long-term high-mileage problems. Due to the direct injection system, the fuel injectors on the L3B are prone to coking.

What is fuel injector coking you ask? It is essentially just a term for carbon deposits on the tips of fuel injectors. As the fuel injectors spray the fuel directly into the combustion chamber, they are exposed to extreme heat and the “leftovers” of the combustion process. Slowly but surely these leftovers (which is essentially just carbon) stick to the fuel injector causing it to first become partially clogged and eventually clog completely. Clogging of the fuel injectors leads to the misfiring of the engine, less engine power, stalling, rough engine idle, and performance. 

Make sure you read all about this in our fuel injector problems article.

High-pressure fuel pump problems (are there really?)

Although some websites out there will claim that there are problems with the HPFP (high-pressure fuel pump) on the GM L3B, we have yet to hear real-life witnesses of such problems. While it is expected that the HPFP will die sometime in the lifespan of a car, there are no reports of common premature failures.

Being a direct-injected engine, yes the 2.7 L L3B engine does use two fuel pumps. A low-pressure fuel pump sits at the fuel tank and makes sure it transports the fuel to the engine. Once the fuel is there, the high-pressure fuel pump makes sure that the fuel gets pushed through the fuel injectors and into the combustion chamber at insanely high pressure (we are talking about 3000 psi). A malfunctioning high-pressure fuel pump will be immediately recognizable as the engine starts stalling, delaying ignition and even not starting at all.

Read all about the high-pressure fuel pump here.

GM 2.7L L3B Fuel economy and horsepower complaints

Before we start, we want to point out that this is merely a complaint and not a reliability problem. A lot of owners have been reporting that achieving GMs promised fuel efficiency of 23 miles per gallon seems to be downright impossible. The realistic figures floating around the internet are more in the vicinity of 19 miles per gallon. It is only normal that a number of owners were outraged by the almost 20% higher fuel consumption compared to the official figures.

The reality here is that the 2.7 L3B engine is just a bit small for the full-size truck form factor. If you want to get the desired power output and feeling, the small L3B engine is just going to have to work much harder compared to a V8 petrol engine. There is just no getting around that fact. If you are interested in saving fuel, buying a full-size truck might not be the best idea to start with. 

While we are on the topic of complaints, another group of owners also finds something else appalling. The 2..7l L3B is just not strong enough! Even though it makes 310 horsepowers at 5600 RPM, it just feels like it is not enough for the big truck. Make sure you test drive this engine before signing the lease, trust us.

Potential Active Fuel Management system problems

The active fuel management system or AFM is an advanced system that engages and disengages certain cylinders based on the driver’s needs. Whenever you are lightly cruising around the town, the system uses a set of special lifters that engage or disengage certain cylinders depending on the engine’s needs. The problem with this system is these lifters. In the 6.2 GM V8 engine, failing lifters can cause catastrophic engine damage. As of recently GM has been replacing the AFM system with a more advanced Dynamic Fuel Management system but the 2.7L L3B engine is keeping the AFM system as for now, it is not causing any trouble. We hope it stays that way.

Major engine problems, not really.

Automotive news sites love reporting on major engine problems. Until we hear actual cases on users’ forums or in real life, we do not like trusting ConsumerReports as a reliable source of reliability stats. According to ConsumerReports a whopping 4% of people have been experiencing major engine problems with the GMC Sierra and the Chevy Silverado. Major engine problems include things such as cylinder head problems, engine rebuilds, etc. But that does not tell us anything that could be linked specifically to the L3B engine. Nor do we know what the background of that issue is. 

We are sure there are isolated engine failures, of any engine, heck even the legendary Mercedes OM616 diesel engines were known to have an occasional breakdown, despite being known as one of the greatest engines in the world.

This is reason enough why we do not accept that news as a reliable source for common problems with a certain car or engine.

No crank, no start, rough idle recall

Soon after the release of this engine, GM issued a recall due to a faulty engine harness that could cause a short circuit to the ground. What that means is there was a potential for an electric circuit flowing into the body of the vehicle. This caused a rough idle, it reduced the engine’s power and it caused the engine not to crank or start.

So is the GM L3B 2.7 L a reliable engine?

I mean when it comes to engines, I really do not understand why and what certain people are complaining about. Yes, it might be a little underpowered, but hey it’s an entry-level engine, what did you expect. Other than that, it is a fantastic engine. Especially when comparing it to my OM642 3.0 Mercedes diesel and even that is considered to be a reliable engine and it has 3X the problems. 

Yes, the GM 2.7 L is most definitely a reliable engine with very little to no major engine problems. The biggest problem in my eyes is the engine carbon buildup which can cause problems if you do a lot of short trips. Keep an eye on the state of the intake manifold and you should be alright. I would definitely recommend this engine and buy it myself as well.

Conclusion

The L3B is one of those engines that gets a bad reputation based on the fact that people have more issues with the fact that there is a 4-cylinder engine in a full-size pick-up truck than based on actual problems and facts. A few voices on the internet can make it seem like there is a lot more going on than it really is. The truth is that 95% or more of the owners have nothing bad to say about this engine and that GM is having more trouble keeping up with the demand than they have repairing all the existing units.