GM Vortec 4.2L inline 6?

JTK

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13,432
Location
Buffalo, NY
What’s the word on this engine? http://media.gm.com/us/powertrain/en/product_services/Photo%20Library/Line%20Engines%204,5,6/06%204.2L%20I6%20LL8%20TB1%20LoR.jpg Any weak spots? Anything specific to look out for? Just picked up a second-hand 2005 trailblazer LS 4x4 & haven’t had a chance to dive into it much yet. The little bit I’ve driven it, she feels incredibly smooth and quiet. Pretty quick too for a ~4500lb truck. Some of the cool things about it: No EGR system, chain driven DOHC, coil-overs, fairly simple single cat exhaust, ~7qt oil sump & (large) oil filter mounts open side up. I know about the fuel efficiency thing. You cant talk to 3 people about a 2002+ trailblazer w/ out 2 of them complaining about MPG’s. So far as I can tell, it’s no worse on gasoline than the 2002 isuzu rodeo 3.2L we traded for the TB. Mid to high teen MPG’s, maybe 20mpg on a good day. Typical for a full framed 4x4 SUV. Thanks fellas! Joel
 

blupupher

Site Donor 2021
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6,938
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Katy, Republic of Texas
Well, I enjoyed it in my 2002 Trailblazer. 18mpg around town and 26 on the highway. Nice strong motor. I know the first year or so of production many complained of piston slap, but I never noticed it.
 
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1,079
Location
Senoia, GA
I have nothing good to say about our former 2003 TB EXT with the 4200 I-6. Poor MPG, NO Torque, no power. Sorry, but I drove a Silverado with a 5300 in it for 5-1/2 years and KNOW what power and fuel mileage is with regards to a GM product. And I wouldn't call the Trailblazer a "Full Size" anything. When a Suburban has more power, more torque and gets better MPG than the Trailblazer EXT, something is wrong. We averaged 13.2 MPG around town and got a measley 19.0 on a nice, flat, easy trip of 600 miles down I-20 to Texas. Seriously disappointed. But it's not ours to worry with anymore.
 

JTK

Thread starter
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13,432
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Buffalo, NY
quote:
Originally posted by thooks: And I wouldn't call the Trailblazer a "Full Size" anything.
Who said anything about full sized? [Roll Eyes] Joel
 
Messages
166
Location
Columbus, OH
I think it's a great fit for the TrailBlazer and its sister vehicles. I pulled a decent sized trailer across Ohio a few times and the thing never broke a sweat. Also, the 4.3L was a great motor, but the one in our old 97 Blazer to this day eats belts. Other than that, great motor, no oil usage despite my brother's neglect.
 
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2,513
Location
Richmond, VA
I had a 4.3 in a 1994 Chevy van and it got good gas mileage and had more power than my Dodge 3.9 six. I had the problem with eating belts too and it was a bad tensioner.
 
Messages
118
Location
DFW area, TX
The new GM inline 6 cylinder engines have been highly reliable and dependable for a completely new motor. The power is close to 300 horsepower now, BUT the key thing is less torque than the 5.3L V-8--not much, but less. Similarly, when the 4.3L Vortec V-6 came out in the light duty pickups, with a 4bbl, it was not much weaker than the similar year 305 4bbl V-8. Only thing that might I've seen, about 70K miles, is the cam phaser starting to leak oil. A simple fix. Probably not an issue in later model years, though. The inline orientation, rather than another V-type motor, was supposedly driven by "only needing one" item for an inline motor versus "needing two" of certain components on a V-type motor. Variable exhaust cam timing results in it not needing an EGR valve, in this case. The smaller 4 cylinder member of that engine family was rated at 30mph EPA highway in a base Colorado/Canyon. Just wish they'd put the 4.2L in those trucks! But then Chrysler would have to put the 5.L Hemi in their larger Dakotas to keep up. Ford? Not in that game right now. Not sure about mpg on the 4.2L Trailblazer, though. As sensitive as newer fuel injection/engine management systems are, the only way to get max fuel economy is to set the cruise and let it do its thing. An incredibly small difference in throttle pedal input (at one given cruise speed) can make the difference in an Instant Fuel Eco readout (on the onboard trip computer) of 17mpg or 25mpg. Punching up the "Instand Fuel Economy" readout on a factory trip computer (that has that function, many have just "Average" readings in some vehicles) can be highly informative on real world fuel use rather than the prior miles/gallons used averages--not to mention how driving style can greatly impact fuel used. The newer Trailblazer SS looks pretty neat too. Enjoy! CBODY67
 

JTK

Thread starter
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13,432
Location
Buffalo, NY
quote:
Originally posted by CBODY67: ..Not sure about mpg on the 4.2L Trailblazer, though. As sensitive as newer fuel injection/engine management systems are, the only way to get max fuel economy is to set the cruise and let it do its thing...
I see that GM added a MAF sensor to the 2006 4.2L. I'm not sure what system is used on the MAF-less 2002-2005, if it goes by MAP or not?!? Too cold out to dig into my 2005 yet [Frown] . My thinking is GM is trying to do some MPG tinkering with it. Thanks Joel
 
Messages
1,043
Location
Central IN
quote:
Originally posted by thooks: I have nothing good to say about our former 2003 TB EXT with the 4200 I-6. Poor MPG, NO Torque, no power. Sorry, but I drove a Silverado with a 5300 in it for 5-1/2 years and KNOW what power and fuel mileage is with regards to a GM product. And I wouldn't call the Trailblazer a "Full Size" anything. When a Suburban has more power, more torque and gets better MPG than the Trailblazer EXT, something is wrong. We averaged 13.2 MPG around town and got a measley 19.0 on a nice, flat, easy trip of 600 miles down I-20 to Texas. Seriously disappointed. But it's not ours to worry with anymore.
Maybe you should have upgraded to the 5.3L V8 since you had the EXT model. I'm not surprised that you were disappointed in the power of the I-6 since you have the EXT model. That EXT model probably adds a decent amount of weight to the vehicle....why do you think they offered the 5.3L V8 in the EXT only? My friend has an '02 TB with the I-6. It's a great engine. Very quiet and his gets decent MPG. He has absolutely zero complaints about his I-6.
 
Messages
1,079
Location
Senoia, GA
quote:
Originally posted by mshu7:
Maybe you should have upgraded to the 5.3L V8 since you had the EXT model. I'm not surprised that you were disappointed in the power of the I-6 since you have the EXT model. That EXT model probably adds a decent amount of weight to the vehicle....why do you think they offered the 5.3L V8 in the EXT only? [/QUOTE] Well, for one, the 5300's without DOD are scarce. Were scare in 2003. Only thing you can have now is the Displacement on Demand. I beleive GM has tried this before and it tanked. Sorry, but I'm not the only one that has owned a vehicle like this (including non-extended Envoys and TB's) that have pretty much the SAME comments. The things are also LOUD. L-O-U-D. Loud. HVAC fan is LOUD. Wind noise at highway speeds- LOUD. The EXT's handling is awful. Your comment concerning the 5300 does have merit, as all of the people I have talked to about the lack of power/torque/fuel economy say the same thing (as I do)- "If it had the 5300, it would probably be tolerable." Then you would expect the poor fuel economy (but surprisingly, the 5300 is GREAT on fuel), but you'd also have power and torque. Sorry, but the sucker has to DOWNSHIFT at 72 MPH on a FLAT interstate highway after the cruise "accel" button is pushed TWICE, it is a complete piece of junk to me. That engine downshifted so many times, and spent so much of it's life at 3,200 RPM's during the 24,000 mile duration we had it. I will be watching carefully at these as they age to 100k and 150k miles. It's a good thing they have a 7 qt sump, as they need a larger collection of oil to protect them. Oh, and I guess someone is going to post and say how an engine spending a considerable amount of it's time above 3,000 rpm's is good for it. Maybe so, but not from one that has "GM Vortec" on it.
 

JTK

Thread starter
Messages
13,432
Location
Buffalo, NY
quote:
Originally posted by thooks: Sorry, but the sucker has to DOWNSHIFT at 72 MPH on a FLAT interstate highway after the cruise "accel" button is pushed TWICE, it is a complete piece of junk to me. That engine downshifted so many times, and spent so much of it's life at 3,200 RPM's during the 24,000 mile duration we had it.
What gears did you have? 3.42, 3.73 or 4.10's? Was it (G80) limited slip? Our 2005 has the open 3.42 rear and it's got enough grunt that the torque converter often doesn't even come out of lockup on an incline. RPM's are under 2K at hywy speed with more than enough power, of course that depends on what you are used to. Changes have been made to the clutch fan and for wind noise improvement as well. G/luck Joel
 
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