4.2L Vortec V6 in Chevy Trailblazer

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So my friend has this engine in his TB, almost 200k and the thing runs like a top. However, I havent known what problems he's had with it and only rode in it once or twice. Are there any known problems with this motor? His is year 2003. Thanks guys!
 
That's actually an inline six, not a V6. One plus is that it *doesn't* have EGR. Always good.

AFAIK it's a good motor, albeit a rare one.
 
It's an interesting engine. Smooth and tons of HP on tap, but you gotta rev it to get the power. I don't think there is any real major issues with the engine itself, mostly Emissions stuff afaik.
 
It’s a great modern I6. It was on the Wards 10 Best list for several years of its production. I often wish GM had put it in the pick-ups. I’m sure that was a cost saving decision… A lot of folks nowadays aren’t used to how smooth an inherently balanced engine is. I6 is probably one of the best production engine configurations it just is not as space efficient as a V configuration.
 
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I have the '04 Trailblazer with the I-6. It's a great engine. I'm using Mobil 1 5w-30 and the oil level is still at the full mark after 6k oil changes.

The city mileage is not good at all but I'm impressed that I can get slightly over 21mpg with my 4X4 EXT version for highway road trips.
 
Originally Posted By: 94MaxGXE
The 2003 4.3 Vortec in the TB is an inline 6.

the i6 was a 4.2. the v6 was a 4.3
 
The only major issue to look out for in the 4.2L I6 is a situation where the intake valve seats are "soft" and cause low compression and a miss at idle. It won't come up straight away on a search, but if you look hard enough, you'll find it.

Ultimately, GM made a lot of these engines and the valve seat issue isn't really a big one. Pretty much, if you've made it to 75,000 miles, you're in the clear as the valve seat issue should have made itself known by then.

That said, I own a 2006 Trailblazer with just over 100K. It's been perfect. The only thing that could make it better would be coupling it to a 6L80 trans. I think the extra two gears would really help with keeping the engine in the upper revs when necessary and, just maybe, add a couple MPG to the fuel economy numbers.

Unfortunately, a long and tall I6 doesn't make packaging easy. While the 4.2L did spawn I5 and I4 variants, ultimately, the platform must be designed around the engine. Unless you're committed to the I6, like BMW and Volvo, this is difficult and costly. GM gave a good effort and came out with a good engine, but I'd imagine that adapting it to other platforms was just too costly and with customer favor trending away from truck-based SUVs and more toward crossovers, the decision to scrap any further development on Trailblazer platform, and it's I6 engine, wasn't a hard one.
 
Originally Posted By: MrHorspwer
GM gave a good effort and came out with a good engine



Did't Isuzu actually build these engines?
 
Originally Posted By: rat
Originally Posted By: MrHorspwer
GM gave a good effort and came out with a good engine



Did't Isuzu actually build these engines?


Nope. The Atlas series of engines was designed by GM Powertrain and the 4.2L was built at Flint Engine South.
 
Agree with addguy, I had a 2004 Trailblazer, loved the SUV, but could not get more than 20mpg highway. Then had a 2005 Colorado I-5, about the same. Seemed to be decent engines, but poor mileage was a downer........
 
Originally Posted By: MrHorspwer
Originally Posted By: rat
Originally Posted By: MrHorspwer
GM gave a good effort and came out with a good engine



Did't Isuzu actually build these engines?


Nope. The Atlas series of engines was designed by GM Powertrain and the 4.2L was built at Flint Engine South.


Yep, that's been a common misconception. It's a complete GM engine.

I also owned one. A 2005 Trailblazer. They are large, very comfortable, versatile and as a result are basically V8 fuel thirsty.

Like said, common issues on the earlier models are ignition coil failure (they use 6 coil-on-plugs), air injection system issues; These models inject air into the head, right into the exhaust manifold stream if I remember correctly. There's an electric air blower under the vehicle. Condensation in that system causes problems. I've heard of maybe 2-3 instances over the years of valve seat issues. Given these engines are chain driven DOHC, it's a major ordeal to remove the head.

The 4.2's hold a boat-load of oil. 7qts IIRC? So you can go a long time between OCIs.

Basic maintenance is real easy on these engines. Pretty much everything easily accessible.

They're coupled to the 4L60E which is a good trans that's been around a long time.

You don't hear of many problems with the 4x4 drivetrain, which is easy to service as well.

Joel
 
We received a Notice from GM that the cylinder liners had a potential problem that could cause catastrophic engine failure suddenly and without warning. No offer to inspect//fix. I don't think they had a way of determining if the problem was there until failure occurred.

Since the 03TB was the wife's ride, and since it was falling apart by 50k miles, we dumped it after receiving the notice.

The engine however was stout, and it responded nicely to higher octane fuel. GM said with better exhaust it could easily produce 300hp. The drivetrain was fine but the rest was junk. The engine was great, powerful.
 
Yes! Good point Ed. I forgot about the cylinder liner deal. I think I've read of one incidence of that on an earlier model, when I owned mine in from 2006-2007.

The bodies are horribly flimsy and the fit/finish is terrible. I agree that drivetrain-wise they're great.

I unloaded mine for a new Cobalt in 2007 because my work commute was killing me at the gas pump with the Trailblazer.

Joel
 
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