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03 Trailblazer 4.2 Sluggish Acceleration

5594 Views 106 Replies 15 Participants Last post by  Trailnut
Hello! New here... Just got an 03 Trailblazer 4.2 with 212k miles on it with some sluggish acceleration. I need to replace the VVT solenoid (have it being delivered tomorrow) but I am not sure if that will still fix the issue. If I do replace the solenoid and its still sluggish, what are other issues that can cause this issue? Ive seen reports of like a clogged Cat Conv but I think it may be transmission related (such as the torque converter) because it has a hard time with hills and then also it has an issue changing gears... Any suggestions would be appreciated!!!
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Did you get this thing on the cheap? That's a lot of crap to have to run down on what I perceived to be a recent purchase. On the plus side, it's not a rotbox being an AZ rig, so worth sinking some coin into if it's going to stay around for a while.
Lots of great things here for me to check! I just did an oil change (though my oil filler cap said to use 5W-30/7qt)
The cap looked fine, wasnt cracked or disgusting... I did throw some Restore in the engine with the oil change to help with any compression issues
The trans fluid I havent checked yet but I will do that, I was thinking of taking it and having the fluid flushed and refilled since it does have 212k miles
Ill check the air filter now and get back to you and as for the fuel filter I have no idea cause I just got the vehicle on the 1st for a previous owner who beat the hell out of it...

I replaced the serpentine belt tensioner and the radiator fan clutch yesterday (was advised to do so by AAMCO) which definitely helped with performance but still sluggish. Ill get these things done and let you all know what I find out!
Not a good idea to have the transmission flushed on any older transmission…unless u bought the vehicle new and have it done at every recommended maintenance schedule in the owners manual, having it flushed could actually cause it to completely malfunction and need rebuilt ….however, I’ve made it common practice to change the transmission filter and gasket and fresh fluid when I buy a vehicle…my trailblazer was a bit sluggish and shifted hard when I first got it..the previous owners never changed the oil it seemed or did any maintaining in it…it helped a lot…

also, with this engine and vvt set up, the owners manual even states to use full synthetic 5w/30 oil …u will want to keep it changed and clean as possible cuz it will damage the screens in the vvt and u will lose power that way as well…they’re very fine screens that oil is pushed through to engage the second cam to get the speed andhorse power…that’s how they get both hp and higher torque out of these suvs…kind of interesting really …one of the two things I love about my trailblazer that’s kept me from junking it lol…the other thing being the turning radius…compare the front steering knuckle of a trailblazer to any other type of pickup or suv…it’s really interesting to see ….
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Not a good idea to have the transmission flushed on any older transmission…unless u bought the vehicle new and have it done at every recommended maintenance schedule in the owners manual, having it flushed could actually cause it to completely malfunction and need rebuilt ….however, I’ve made it common practice to change the transmission filter and gasket and fresh fluid when I buy a vehicle…my trailblazer was a bit sluggish and shifted hard when I first got it..the previous owners never changed the oil it seemed or did any maintaining in it…it helped a lot…

also, with this engine and vvt set up, the owners manual even states to use full synthetic 5w/30 oil …u will want to keep it changed and clean as possible cuz it will damage the screens in the vvt and u will lose power that way as well…they’re very fine screens that oil is pushed through to engage the second cam to get the speed andhorse power…that’s how they get both hp and higher torque out of these suvs…kind of interesting really …one of the two things I love about my trailblazer that’s kept me from junking it lol…the other thing being the turning radius…compare the front steering knuckle of a trailblazer to any other type of pickup or suv…it’s really interesting to see ….
Turning radius is fine in 2wd. 4wd it has a terrible bind when turned sharply.
4wd it has a terrible bind when turned sharply.
Of course. The transfer case isn't allowing for the difference in turning radius between front and rear wheels.

TOTALLY normal.

Some "AWD" transfer cases have a viscous coupling that allows it to act as a front/rear differential...but that limits how much torque can be directed to the front unless there's some method to lock it up like a 4WD.
Of course. The transfer case isn't allowing for the difference in turning radius between front and rear wheels.

TOTALLY normal.

Some "AWD" transfer cases have a viscous coupling that allows it to act as a front/rear differential...but that limits how much torque can be directed to the front unless there's some method to lock it up like a 4WD.
I guess this is what I get for trying to shorten up my comments. I understand it. I was just making a remark to the turning circle reference.😊
Curious how'd everything go? New VVT solenoid make a noticeable difference? Did you check the compression? Was the cat clogged? Did new plugs and coil fix the #3 cyl issue? What'd ya decide to do in regards to transmission? And I just wanted to add keep an eye on your water pump, I was told if fan clutch is bad the water pump will soon follow and vise versa. I needed a new water pump and bought them as a set and just did them together.. There is a weep hole on the water pump that will slowly leak coolant out to indicate the pump is failing. Be aware of your coolant level and pay attention to any new fluid stains where you park and you'll catch it before it completely fails and you overheat, not a bad idea to toss a piece of cardboard underneath when you park for the night especially if it's unpaved. And check oil level often Ive noticed these 4.2L tend to burn oil.
Dirty engine oil can cause sluggishness as well.
Is the check engine light on? Does it work?
Simple items you can do yourself.

Do the simple stuff first:
Engine oil change. Use the correct oil - 10W30. 7quarts on the 4.2 inline 6 cylinder.
What does the inside of the oil filler cap look like?
Is transmission fluid up to the full line? Uses Dexron VI. Top it off. What does it look like?
Is the air filter totally plugged up or can you see sunshine through it? You'll need a screwdriver to get it out.
When was last time fuel filter was replaced? Google how to change it - no jack needed.

Then, like Ravalli says, have a muffler shop check for plugged cat. At 212K, that's a good bet, but what I've listed above are maintenance items which will need to be done regardless since we have no maintenance history on the vehicle.

DO NOT shoot the parts cannon willy-nilly or you may see lots of hubby's money go bye-bye.

Welcome to the Forum!
Don't be afraid to ask questions as none of us are mind readers!
I would use 5w30
Dirty engine oil can cause sluggishness as well.
Is the check engine light on? Does it work?
Simple items you can do yourself.

Do the simple stuff first:
Engine oil change. Use the correct oil - 10W30. 7quarts on the 4.2 inline 6 cylinder.
What does the inside of the oil filler cap look like?
Is transmission fluid up to the full line? Uses Dexron VI. Top it off. What does it look like?
Is the air filter totally plugged up or can you see sunshine through it? You'll need a screwdriver to get it out.
When was last time fuel filter was replaced? Google how to change it - no jack needed.

Then, like Ravalli says, have a muffler shop check for plugged cat. At 212K, that's a good bet, but what I've listed above are maintenance items which will need to be done regardless since we have no maintenance history on the vehicle.

DO NOT shoot the parts cannon willy-nilly or you may see lots of hubby's money go bye-bye.

Welcome to the Forum!
Don't be afraid to ask questions as none of us are mind readers!
I wouldn't use 10w30 only 5w30, and I doubt dirty engine oil would cause sluggish acceleration either...it could be a dirty fuel filter, how long has it been since you changed plugs and air filter ?
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