need more power

[corky]

for some reason my 03 trailblazer runs great at of 60 mph but when i hit hills it wants to slow down and then keep downshifting untill it hits first which really winds up the engine and cant be good. do any of you others have this same problem, is there something i can delete, or add to gain better performance or more power granted i have almost 300,000 miles on it but i did just install a new transmision as the original final gave up. when i see performace modules they dont ever seem to include the trailblazer unless someone knows something I dont which is entirely possible. Thanks for any ideas or advice.

 

[mrrsm]

300,000 Miles in the Rear View Mirror...?

Hmmm... First Impression?

Clogged Catalytic Converter

How to Diagnose the Issue?

(1) CAREFULLY Unwind the Upstream Oxygen Sensor from the Exhaust Manifold ... AFTER first unplugging it from the O2 Harness Connector and being very careful NOT to Nick or Kink or Twist that Short Black Sensor Wire while it is coming OUT and likewise, later on when it is going back IN.

(2) Take it for a SHORT Test Drive under the same observation speeds & conditions and see if your Throttle Response, Engine Power and Torque and Better Shifting returns.

(3) If it does... You'll need a Brand New, OEM Quality CAT R&Rd in there.

(4) Put some Anti-Seize in the Lead Threads on the Upstream O2 Sensor B4 replacing it... using due care not to get any inside of the Cubic Zircon innards.

Mind that you use the Proper Tools to get that "Thing" out of there and Right Back In... because if you accidentally 'BOOGER UP THE FLATS'... You'll be wishing that your Mom... Never Met Your Dad... and besides that, THIS O2 Sensor R&R Tool Kit is a BARGAIN at 37% Off (Less than $20.00) over on Amazon...using THIS GMT Nation Link:

https://www.amazon.com/dp/B0725J3LGC/?tag=gmtnation-20

 

[TollKeeper]

I would also suggest a Fuel Filter.. Engine may be starving for fuel, especially if its the OEM.

Mind you, it could not be the problem. A fuel filter is often the most over replaced part on any car. But its a easy, and cheap part... Usually!

My trucks, Envoy with 212k, and Saab with 168k, are still on the factory fuel filter.

 

[corky]

I would also suggest a Fuel Filter.. Engine may be starving for fuel, especially if its the OEM.

Mind you, it could not be the problem. A fuel filter is often the most over replaced part on any car. But its a easy, and cheap part... Usually!

My trucks, Envoy with 212k, and Saab with 168k, are still on the factory fuel filter.

Just replaced the fuel filter last week

 

[Mooseman]

when i see performace modules they dont ever seem to include the trailblazer

Those eBay performance modules are compldte BS. The only thing that can enhance power and transmission shifting is a tune. But even a tune is not a fix for age or an actual issue.

Air filter I imagine was checked and is good?

How are the fuel trims and how well is the O2 sensor working? Although it may not be throwing a code, it may be getting lazy or your trims are a little out but not enough to trigger a code.

And again, I would investigate the possibility of a clogged cat. Either try the O2 sensor removal test or perform an exhaust backpressure test.

 

[corky]

Those eBay performance modules are compldte BS. The only thing that can enhance power and transmission shifting is a tune. But even a tune is not a fix for age or an actual issue.

Air filter I imagine was checked and is good?

How are the fuel trims and how well is the O2 sensor working? Although it may not be throwing a code, it may be getting lazy or your trims are a little out but not enough to trigger a code.

And again, I would investigate the possibility of a clogged cat. Either try the O2 sensor removal test or perform an exhaust backpressure test.

The problem seems to be mostly around 50 miles an hour, when i want to speed up it just doesn't want to and wants to kick down to far to start really accelerating, ill try the 02 sensor and back pressure test next, but on the back pressure test how do you tell if ots the cat or muffler thats bad.

 

[mrrsm]

Older Engines can suffer from a reduction in power from the Loss of Compression across all of the Cylinders. This comes from the accumulation of Carbon and Gas Gum Lacquer Build Up that can Trap or Pin the "Low Tension" Upper Compression Rings deep inside of the Lands and Grooves of the Pistons.

If you Pull The Engine Oil Dipstick and can detect the Heavy Odor of Gasoline... this would add to the confirming symptoms of this as a Cause & Origin for having Low Power and Pep. Having a Noisy, "Slappy" sounding Engine at start up is also a strong indication for the presence of this problem.

Your Very High Mileage Engine Performance might generally benefit from having an ACDelco TEC (Top Engine Cleaner) Solvent Treatment as outlined in THESE linked Threads:



However, this additional Diagnostic - Maintenance Step deserves consideration only AFTER the R&R of the Upstream O2 Sensor is conducted to eliminate the possible problem of having a Clogged CAT.

And while being a bit tedious... the ACDelco TEC Treatment does NOT involve the need for any invasive manual engine component disassembly... just keeping the appropriate attention to the safety issues and procedural details from Start to Finish:

Carbon cleaning the 4.2L LL8. Experiment

I have recently performed carbon cleaning on the pistons and valves using a method recommended by @MRRSM and I figured to document the experience for those who would like to pursue this in the future. The method involves pouring AcDelco Top engine cleaner in the spark plug holes. This is NOT a...

gmtnation.com

A.C. Delco Foaming Top End Cleaner....

Good Evening All, I've read about this procedure here on the forum. I'm wondering if it would be OK to do, regardless of if I have carbon build up or oil consumption. I have noticed a small amount of oil accumulated in the intake plenum. I do have a little piston "slap" that goes away upon...

gmtnation.com

 

[Mooseman]

but on the back pressure test how do you tell if ots the cat or muffler thats bad.

First test at the upstream sensor bung and then at the downstream. If the downstream backpressure is lower than the upstream, it's the cat. If higher, it's the muffler.

Older Engines can suffer from a reduction in power from the Loss of Compression across all of the Cylinders.

That brings up a good point to do a compression test. This would give an idea of the overall health of the engine mechanically.

The problem seems to be mostly around 50 miles an hour, when i want to speed up it just doesn't want to and wants to kick down to far to start really accelerating

That brings up the possibility of a problem with the transmission? What's the maintenance of it like? Fluid level and condition? May be worth it to do a fluid and filter change. Maybe the Torque Converter Clutch isn't releasing properly. While cruising at 50, try tapping the brake with your left foot while holding the speed steady to disengage the TCC and see if the RPM increases slightly indicating the clutch is releasing.

 

[mrrsm]

Without Beating The Living Hell out of the Topic of "Why Not Use an Oscilloscope ?"...TOO Much, I would like to add to @Mooseman 's suggestion on performing a Dry-Wet Compression Test on ALL Six Cylinders.

If you have an inexpensive PICO or Hantek Scope and a High Amperage Clamp tucked in around the B+ Red Battery Postive Cable...you can very easily and quickly perform a "Relative Compression Test" ...which comes with some distinct and ready advantages:

(1) It is COMPLETELY Non-Invasive.
(2) The "O" Scope Set Up is Very Straightforward and QUICK.
(3) The Results can be revealing about the need to continue to the Dry-Wet Testing.
(4) The Starter Health and In-Cylinder Balance or Imbalance Issues will become Obvious.
(5) It should be Part and Parcel to EVERY Mechanic's Diagnostic Approach.

THIS is what a Nominal Relative (Healthy) Compression Test SHOULD Look Like:



Adam will explain what all of the "Squiggles" mean in THIS Video covering the Step By Steps (He will place the High Amp Clamp on the NEGATIVE Battery Cable...which also works just as well) that WILL Apply in ALL Cases, regardless of the Brand-Make-Model of the "O" Scope...or Brand-Make-Model of ANY Vehicle being so Tested:

 

[corky]

First test at the upstream sensor bung and then at the downstream. If the downstream backpressure is lower than the upstream, it's the cat. If higher, it's the muffler.


That brings up a good point to do a compression test. This would give an idea of the overall health of the engine mechanically.


That brings up the possibility of a problem with the transmission? What's the maintenance of it like? Fluid level and condition? May be worth it to do a fluid and filter change. Maybe the Torque Converter Clutch isn't releasing properly. While cruising at 50, try tapping the brake with your left foot while holding the speed steady to disengage the TCC and see if the RPM increases slightly indicating the clutch is releasing.

Trans and torque cot are brand new but i did notice today that of im sitting in park and floor the accelerator it wont go over 2000 rpms shouldn't it redline

 

[mrrsm]

There is another Simple Diagnostic that can be performed on the Catalytic Converter that involves sliding a Large Cardboard Section underneath the passenger side of the SUV and after laying down upon it... Take a 'Dead Blow Hammer' and VERY GENTLY ...TAP-TAP-TAP underneath the Stainless Steel CAT Can while listening for THESE Chunks of Ceramic Honeycomb to sound like "Coins Being Dropped inside of a Large Ceramic Bowl". Once shattered... these Broken Pieces can obstruct the through flow of the Exhaust Gas Stream:



Source: Broken Catalyst:

https://www.2carpros.com/articles/engine-has-low-power-output

Also... Here are some Close Up Un-Boxing Images of that inexpensive In-Cylinder Compression Test Kit that is the one worth getting via this GMT Nation Amazon Link:

https://www.amazon.com/dp/B00SKSAB8U/?tag=gmtnation-20

 

[corky]

There is another Simple Diagnostic that can be performed on the Catalytic Converter that involves sliding a Large Cardboard Section underneath the passenger side of the SUV and after laying down on it... Take a Dead Blow Hammer and VERY GENTLY ...TAP-TAP-TAP underneath the Stainless Steel CAT Can while listening for THESE Chunks of Ceramic Honeycomb to sound like "Coins Dropped inside a Large Ceramic Bowl". Once shattered... these Broken Pieces can obstruct the through flow of the Exhaust Gas Stream:

View attachment 108033

Source: Broken Catalyst:

https://www.2carpros.com/articles/engine-has-low-power-output

Also... Here are some Close Up Un-Boxing Images of that inexpensive In-Cylinder Compression Test Kit that is the one worth getting via this GMT Nation Amazon Link:

https://www.amazon.com/dp/B00SKSAB8U/?tag=gmtnation-20

View attachment 108034View attachment 108035View attachment 108036View attachment 108037View attachment 108038

I did notice today that if im sitting in park and rev up the engine it will barely go over 2000 rpms is that normal or should it redline.

 

[mrrsm]

Ordinarily, I would think there was something going on here akin to a "Reduced Power Mode"... but the conditions which set that RPM event to occur usually results in having a HUGE reduction in the Vehicle Speed (for the sake of Safety) due to the PCM being confused about the ACTUAL positions of the ACC Pedal #1 & #2 Signals and the ACTUAL position of the Throttle Body Butterfly Plate... or perhaps from having a Damaged, Dirty or Compromised MAF-IAT Circuit (...which the 2003 Trailblazer does NOT have incorporated into its design).

So that just leaves something "Mechanical-Physical" to get in the way. So... You really owe it to yourself to Investigate the Prior Suggestions to Pull the Two O2 Sensors ...and then Take it for a Test Drive.

"Well Done... Is Better than... Well Said..." Benjamin Franklin

 

[Mooseman]

I did notice today that if im sitting in park and rev up the engine it will barely go over 2000 rpms is that normal or should it redline.

It has a park/neutral rev limiter. Only way to defeat it is to be rolling and put it in neutral.

 

[budwich]

for some reason my 03 trailblazer runs great at of 60 mph but when i hit hills it wants to slow down and then keep downshifting untill it hits first which really winds up the engine and cant be good. do any of you others have this same problem, is there something i can delete, or add to gain better performance or more power granted i have almost 300,000 miles on it but i did just install a new transmision as the original final gave up. when i see performace modules they dont ever seem to include the trailblazer unless someone knows something I dont which is entirely possible. Thanks for any ideas or advice.

So this condition has existed since replacing the tranny.... Ie. your "new tranny" has never "functioned correctly".

Another check that you can do, is run with the gear selector set to 3rd (ie. not Drive). Does the truck then function OK...ie. you can speed up to 50-60 and go up a hill without it kicking down to 1st? You wouldn't happen to be trying to use wide open throttle going up the hill...

 

[corky]

Update on my truck, so back pressure gauge confirmed bad catalytic but also the pvc hose on the left side of the engine was clogged so now the truck runs freakin great again, thanks everyone for their input.

 

[corky]

this is the cut away view of the cat.

 

[mrrsm]

Astonishing ... and in part is Emblematic of what can happen if P0300 or an accumulation of Engine Mis-Fires happens or the use of very Low Grade Fuel occurs again and again over time. One other artifact present and worth noticing is the result of having Bad Gel-Filled Bulb Style Motor Mounts.

The Engine can shake violently enough to release Flakes of Rust breaking off of the inner Cast Iron Exhaust Manifold segments and collecting as a durable blockage to the passing exhaust stream. In these images... you can see the external artifacts of this... but the same problem happens internally as well, remembering that a substantial portion of the by-products of combustion... is Water:

You may well ask, "But... Bad Motor Mounts...?" Yes... If you look closely at the attached images below... Observe where the Cast Iron Metal is freshly exposed...Gray and Un-Rusted at the Junction where the Small Down Pipes meet at the collection point. You can see that the majority of the Rust Flaking happens in concentration.

This is because the Engine is being allowed too great a realm of motion as the Engine RPM Rises and Falls and the Engine Block moves Left and Right... from Engine Torque causing the motion of the Exhaust Manifold to fight against the Exhaust Flange and pipe leading down to the Catalytic Converter.

This constant bending motion along with changes in Temperature encourages the Rust Flakes to dislodge and move head long from Exhaust Gas Pressure up against the face of the Ceramic Honeycomb in the opening of the CAT S/S Can. What you can see happening on the Outside also happens ...On the Inside:



There IS a way to Test this Theory... Rust as FE2O3 is *Mildly Magnetic"... so if you can pick up pieces of that dislodged detritus scraped off the facing of the Honeycomb with a Neodymium Magnet... All will be Revealed.

Hmmm... I wonder if this could also be accomplished by going through the Upstream O2 Port using THIS to first Inspect for the issue...and then Cleaning Off all of that Rusty Crap...Using Compressed Air through a Narrow Plastic Pipe ... Perhaps?



One Last Suggestion...

You might request a Title Change from the present one that is a bit vague and perhaps confusing...to something like, [SOLVED] A Clogged CAT Can Caused My Power Loss

 

[corky]

Astonishing ... and in part is Emblematic of what can happen if P0300 or an accumulation of Engine Mis-Fires happens or the use of very Low Grade Fuel occurs again and again over time. One other artifact present and worth noticing is the result of having Bad Gel-Filled Bulb Style Motor Mounts.

The Engine can shake violently enough to release Flakes of Rust breaking off of the inner Cast Iron Exhaust Manifold segments and collecting as a durable blockage to the passing exhaust stream. In these images... you can see the external artifacts of this... but the same problem happens internally as well, remembering that a substantial portion of the by-products of combustion... is Water:

You may well ask, "But... Bad Motor Mounts...?" Yes... If you look closely at the attached images below... Observe where the Cast Iron Metal is freshly exposed...Gray and Un-Rusted at the Junction where the Small Down Pipes meet at the collection point. You can see that the majority of the Rust Flaking happens in concentration.

This is because the Engine is being allowed too great a realm of motion as the Engine RPM Rises and Falls and the Engine Block moves Left and Right... from Engine Torque causing the motion of the Exhaust Manifold to fight against the Exhaust Flange and pipe leading down to the Catalytic Converter.

This constant bending motion along with changes in Temperature encourages the Rust Flakes to dislodge and move head long from Exhaust Gas Pressure up against the face of the Ceramic Honeycomb in the opening of the CAT S/S Can. What you can see happening on the Outside also happens ...On the Inside:

View attachment 108812View attachment 108813View attachment 108814

There IS a way to Test this Theory... Rust as FE2O3 is *Mildly Magnetic"... so if you can pick up pieces of that dislodged detritus scraped off the facing of the Honeycomb with a Neodymium Magnet... All will be Revealed.

Hmmm... I wonder if this could also be accomplished by going through the Upstream O2 Port using THIS to first Inspect for the issue...and then Cleaning Off all of that Rusty Crap...Using Compressed Air through a Narrow Plastic Pipe ... Perhaps?

View attachment 108815View attachment 108816

One Last Suggestion...

You might request a Title Change from the present one that is a bit vague and perhaps confusing...to something like, [SOLVED] A Clogged CAT Can Caused My Power Loss

I ordered a new dorman exhaust manifold wich i will probably port match to the gasket and since i dont have to worry about emission testing im thinking about cleaning out the old cat and reinstalling it, the replacement i ordered said exact fit but failed to mention it was a smaller diameter pipe and the cat was about a third diameter of the original, i guess you get what you pay for.