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03 Trailblazer 4.2 Sluggish Acceleration

5622 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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Pressure test for a plugged cat first --- it's cheap and a slam-dunk easy test at almost any muffler shop.
When you say cheap, how much are we talking? Im working with my hubbys money rn while he's over seas so I need to know how much to ask him for the money
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!
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!
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Don't flush the transmission ... service it correctly by dropping the pan and then you can see inside to get a decent appraisal of it.

Tear the old filter apart to see what it's caught and clean the magnet to see how much ferrous material it caught too.

Those things won't be done by flushing. You dont need to replace all the fluid every time ... besides, I would never allow my customers to risk crippling their vehicle by flushing.

I've had overhauls created by other shops that did flushing. It's just risky on an older unit.

PS ... the reason why I recommend the drill-and-screw pressure test is because not many people have the special socket to remove an oxygen sensor without damaging it.

PPS ... don't take any advice from AAMCO. That's like going to a witch doctor for orthopedic surgery. Belts, hoses and a wax job won't fix performance issues.
I mean I did do my own check at home once AAMCO gave me the advise to see how the parts were and they definitely needed to be replaced. The shaft for the fan clutch was cracked and splitting and the tensioner was weak (not horrible but definitely showed signs of low tension and risked belt slipping)... The VVT solenoid they said was completely dead and I had my brother confirm this hence why im replacing that as well... As for the transmission, Im not really comfortable doing any of that work myself because I know if I mess that up then thats gonna be an expensive screw up
I couldn't disagree more on not flushing the transmission. I flush everything I own no matter the miles and have yet to kill one. Granted I don't do it to try and fix something, rather old, nasty, varnished fluid simply cannot perform as well as fresh fluid. I drop the pan, put a new filter in, and refill. Next I pop off the return line, shove a hose over it, and put that in a milk jug. Fire up the car and let the tranny do the pumping. Fill 3 gallon jugs and you're good and clean.

Also OP, was this thing ever not gutless? I'm wondering if when it's all 100% it won't be up to what you're expecting? They're not rocketships.
Im honestly just trying to make it so the trailblazer can tow a small trailer from AZ to New Hampshire when my hubby gets out of the Marines... I replaced the VVT solenoid just now and im waiting for the codes to clear so I can drive it around the next couple days but some codes that did pop up were P0420 (Catalyst System Efficiency Below Threshold Bank 1) and P1345 (Electrical Short: Ignition Coil Output Stage 3) not including the P0014 ('B' Camshaft Position Timing Over-Advanced Or System Performance Bank 1) I am NOT getting any codes regarding the transmission which I am glad for, I just want to change the fluid because it has 212k miles on it
If the trans is healthy absolutely flush it the way I described, it will buy you life in the long run. How big of a trailer do you want to tow? My sister had a 06ish 4.2 TB and I used it to tow Uhaul's biggest trailer from MI to CO. I kept it in 3rd gear the whole time and it was a champ the whole way, zero mods. The catalyst code may be a second order effect of the other stuff. If I were you, I'd swap #3's coil with another and see if the code stays or follows. If it follows, you know it's a junk coil.
Good to know, ill give that a try... As it was I was thinking of replacing all the plugs and coils anyway cause no one replaces t hose until theyre bad... As for trailer size, we were wanting to get a 14x6 cargo to convert into a camper after the move and stuff... Nothing crazy
Look, all I know is the transmission fluid is black and smells burnt... it needs to go period... As of right now, I cleared the codes and I will see what pops back up (if anything) in a couple days after driving it around and what not... Ill post again on saturday with what ever codes popped up and go from there
Regardless of your stance on the transmission fluid flush, cylinder 3 has something up so expect that to return.
Yeah I already priced the ignition coil from Rock Auto... will order it tomorrow after work... Also Ravalli, Its kind of hard to trust the advise from someone who suggested to drill a hole in my muffler/cat converter...
So tried driving the trailblazer to work and its still bogging really bad on hills and stuff, not even steep ones, im talkin like... 15 degree at the most...
Do you have a listing of the current OBDII codes? Also, is the Reduced Power light illuminated on the instrument panel?
I cleared the codes yesterday so I am waiting for the computer to catch up and stuff... It did give a P0420 and a P0014 but thats it... I am not seeing a diminished power light on my dash, just the ABS light and that my ebreak is engaged (even though its not, I need to adjust/replace the parking break pads)
Thanks. Did you see my earlier post to you about the ignition coil?
Yes, I just need to get it ordered so I can replace it
OK, but your coil may not be bad. Did you get either a P0300 or a P0303?????
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I do not know what OBD II code reader you are using, but the definition shown for P1345 is incorrect.

Here is a link to a website that explains what P1345 means :

If you want just google this - 2003 Trailblazer P1345 for yourself and see that the code reader you are using is wrong.
So I know I had to replace the VVT solenoid but I was told that I wouldnt have to re-adjust the camshaft position with the broken solenoid...
So what is my solution to the problem then? x.x
I already replaced the VVT and its connector is completely fine... I will look at the camshaft position sensor once I figure out where its and and check its condition
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Nothing cracked or damaged and the connector wasnt oily or anything, just a little dusty on the outside...
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So I tried to get my dad to help me do that test and he just said no and took me to go buy a new sensor so... yeah... guess we'll see how that goes lol
K so swapped that out and took it for a test drive... seemed to do better until I tried to take it onto the highway to test its climbing to see if it was any different ant it wasnt... It still bogs hard on shallow inclines and the transmission is still s hifting hard (after 3k+ RPMs)
No need to use a pressure Guage just remove the upstream o2 sensor and then drive to see if the power is better. Will be loud but won't hurt anything
Ill try this once I can get my hands on an O2 sensor socket...
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