Modifications to 2007 Chevy Trailblazer

Hey all. Wanting to get more HP or better performance out of the 4.2L I6 in this 2007 Chevy Trailblazer. Any ideas that might be worth pursuing? I saw where people have mention the pcm4less, or something like that, but I’m not sure how exactly it works or what it can do. Even if I could go the other way, towards better gas milage, that would be fine as well. Kinda wondering about the range of modifications in terms of difficulty, efficiency, and of course cost. Thank you all.

My Traiblazer 6 cyl was just fine, never felt the need to worry about performance increases. Are things going south?

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I’d bet a dozen donuts that the pcm place is worthless. I’d be surprised if there was any inexpensive way to get hp, you typically need to add a turbo or a supercharger, at great expense. Money would be better spent getting it in top mechanical condition.


PCM4Less is a tuning company. You either go to their facility in Ohio or you send your engine control computer to them and they change the parameter file in the computer to boost whatever you ask them to try and boost, horsepower or mileage.

Since your 6 has no turbo or supercharger from the factory, there is little you can gain in HP. Turbo cars can command higher boost and therefore higher HP. Tunes can work very well for those engines. To boost HP on your 6, timing is increased and will require premium fuel all the time… for 10-15 hp added to your 270 hp.

As for other modifications… the follow-up question to “how much HP can I get” is is always “how much can you spend?”

This is not a popular engine, there are not too many parts available. To make more power, you’d need new cams, valvesprings, upgraded intake system and exhaust including headers. That, I’d estimate, is at least $3500 in parts alone and you’d need some dynomometer time to tune the engine computer to match the new parts. Labor you run another $1000 or so. Figure $500 for the dyno time and $500 for the guy that does the tune. That $5500 buys you maybe another 70 hp.

And this ALL depends on the condition of this 13 year old xxx,xxx mile (you don’t say) engine and transmission. Reality is not the same as TV, where cost is no object.


I have a 2008 it is not lacking for power at 285 hp out of that great straight six they use in the platform . If it has been any time at all since a tuneup then go get 6 AC/Delco 41-103 iridium plugs and install them . It is never going to be thrifty , get at best 22-23 highway on the 4.2 liter 6 . Also clean the throttle body then reset the PCM this will smooth out the idle .

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Those also came with 5.3L and 6.0L v8, right? If you want more power, get one of those, if you want mpgs, keep yours and make sure it’s in top tune.

And, it should be noted that increasing the power output of a 13 year old engine is likely to make its remaining lifespan even shorter.

Additionally, there is the question of whether the 13 year old transmission would take kindly to efforts at stronger acceleration.

How often has the transmission been serviced over the years?
If it hasn’t been serviced at least 3 (preferably 4… ) times, the transmission is likely not long for this world, and forcing it to endure stronger acceleration runs will only shorten its life.


If you want a noticeable boost in power, sell this one and fine a Trailblazer with the 6L LS2 engine. It has
390+ HP and 400 lb-ft torque.

Also, do you live someplace that does not have emissions testing. At more than one hp per cubic inchthat engine is already pretty efficient. The factory has already done all the cheap and easy stuff. Getting more will be expensive. In the realm of 'If you have to ask, you can’t afford it."


The engine itself is at about 125,000. I think there may be a vaccum leak, and that’s a strong maybe, but other than that possibility, the engine is in great shape, with no problem or codes. I am the second owner of the vehicle and the previous owners actually kept record of having it serviced every step of the way. They had the money to do so. That’s partially why I was interested in doing a few things to it within reason. Thank you though for all the very much valued input

Yes. I live in Florida. No emissions testing here.

Nope. Things are actually great. The vehicle has no codes or problems. Anything wrong with it is just cosmetic, minus a potential vacuum leak.

Is it getting close to its original mileage and performance or is something degraded? Ensure that everything is operating correctly - good plugs and ignition system, clean and not worn injectors, are inlet air controls, vacuum lines, EGR and oxygen sensor still good? That’s the easy stuff. As for modifications, its design was optimized for some combination of emissions, fuel economy, and performance - these interact, change one and something else is likely to go out of balance and you might not pass smog testing, or you might have premature cat. failure, etc.

Low risk mods that can add up:

  • Remove unnecessary weight - last winter’s chains, tools, rear seat, etc.
  • Mount quality, low rolling resistance tires, consider inflating a few pounds over the nominal pressure (but nothing stupid).
  • Look for synthetic oil and gear lubes with published viscosities at the lower end of the allowed ranges, same for transmission fluid provided you can find a compatible type. Change before worn out.
  • You might be able to reduce breathing losses at intake and exhaust, but be careful not to compromise filtering.
  • Changing driving habits can offer the biggest gain - drive smoothly and watch traffic and signals a quarter of a mile ahead to minimize unnecessary acceleration and braking. In steady traffic, use the highest gear you can without lugging. If you like gauges, mounting a manifold vacuum gauge and an instantaneous fuel consumption meter will tell you most of what you need to know.
  • Just small things like allowing the car to gradually slow ~ 5-8mph going up hills (traffic permitting) followed by running over by that much down hill (don’t get a ticket) can inprove mileage by ~ 10-15%, absolutely free and likely more than you’d realize from a tune.

Botard ( another screen name for the list of strange ones ) did not ask about increasing Miles per Gallon , he wants more power out of a vehicle that very few people modify.


“… Even if I could go the other way, towards better gas milage, that would be fine as well.”

Correct. It was mostly to see about increasing horsepower but I was curious to see what could be done in terms of more horsepower/less gas milage or the opposite. Thank you.

The screen name, lol, was given to me by a friend back in middle school before I had my first email, haha. Obviously, I just decided to keep it. I think it has been used other places though.