Loss of power....

[JK171]

So recently I've noticed after I start my 02 Trailblazer up once it's been sitting for a few hours it seems so lose some power when climbing hills for a couple seconds. For example I live on a hill when I go out in the morning after it runs for a couple mins I'll throw her in drive and accelerate it seems to bog for about 5-6 seconds then kicks into gear and drives normally. I'm not getting any lights or codes and nothing I've read on here really pertains to my situation. I just bought this truck about a month ago still getting used to it maybe it's the age? Has this happened to anyone else?

 

[JK171]

I should also add that it's shifting from 1st to 2nd then 2nd to 3rd somewhere around 3500 rpms when driving is this normal on TB's?

 

[djthumper]

How many miles? Maintenance history? Have you cleaned the throttle body recently?

 

[JK171]

150,000 miles, only had 1 owner before me I have receipts from all the oil changes no serious mechanical issues. I just cleaned the tb last week actually.

 

[djthumper]

Did you reset the PCM? Have you changed the fluids in the transmission, transfer case and the others below? Do you have any CEL and codes showing?

 

[forrestnummy]

I have been chasing the lack of acceleration and sluggish I6 for way too long. The issue is a vacuum leak, that no one has seem to of found. I have seriously replaced everything on my TB '04. Never could find the secret vacuum leak. Well I found it and yall will not believe it, but I think your gonna love me. I tested the entire side of the engine. NO vacuum leaks. I tested the brake booster. it held at 20-21 psi (I think that's right, from memory) Never did I test the brake booster check valve. Why would I? We its a very cheap part, so I changed it. My TB runs like a champ. For over 2 weeks now, I have not had any power issues or stumble. All power and acceleration has come back and she runs like she is new. Even brakes and stops like it was new. The reason for the brake booster check valve causing the vacuum leak is this. It is supposed to be a one way valve. It holds the pressure for your brake booster but the valve can get weak or fail. So it either wont seal or stays sealed or open. I don't know what mine was doing, but it sure was not doing its job. I LOVE my TB again. I really hope that I help someone. I could not keep this to myself. I know how many people are out there that have lost their mind over this loss of acceleration and sluggish, junk. I know that a brake booster check valve sounds crazy, but its @ $11-$20 on amazon. Its insanely easy to swap out. No reason not to give it a shot. I seriously was about to take my TB into the transmission shop because it wasn't shifting right or stopping right. I also already have a new brake booster and master cylinder, ready to go, but this little valve solved SO SO many issues.

 

[Sparky]

Dang, makes me wonder if that was partially my problem on mine too.

Lately I've come across a few things that sound like what I had been noticing for some time without ever figuring out what it was while the truck was still on the road

 

[Capote]

Seems like a transmission issue to me. I've gone through two rebuilds so far...

 

[Zachary Costilla]

If you dont mind me asking, whats the part number or where did you get that check valve? I'm thinking this might be the cure to my envoys ailment as well!

 

[mrrsm]

FWIW... This also sounds like it might be symptomatic of having a Clogged Up Catalytic Converter. On very high mileage vehicles or those over a decade old...in may cases...Huge Flakes of Rusted Metal coming from the interior walls of the Cast Iron Exhaust Manifold can break off from the inside as the engine vibrates more and more from bad motor mounts. As they drop free and get moved along in the exhaust stream... they get pushed up inside the CAT and tend to flatten out on top of the Rare Earth Metal Impregnated Ceramic Honeycombs inside and either obstruct the exhaust flow and increase Back Pressure....or in some case...impact directly into the Honeycombs and fracture them into collapsing and blocking the flow of the exhaust as well.

 

[forrestnummy]

Im on my 4th cat. Mine was not a cat issue. But when you run rich too long you will destroy them. Just FYI. I have a new super50 muffler and magnaflow cat. Resonator is GONE!!! 3 inch in and out. Don't let people lie and say you will lose power on the back pressure. Its an all in you head myth. The check valve was a leak, and I have put a new one on a few friends GM and chevy and they have noticed a performance boost. Im not saying that this is everyones problem. I have almost rebuilt my entire TB. Almost everything inside of it is new. I did replace the throttle body harness and the camshaft variable timing solenoid, power plug too. I had issues where I would get all my power, then after a turn or a bump, it would lose that "pep". So I changed out the throttle body harness, due to the recalls I saw on them. Chevy never actually admitted the flaw in our throttle body harness, but they did on the tahoes. They didn't run enough cable and the last 3-4 inches of cable, to the plug, were put under so much stress and heat, that the cables fail. GM states that the stress on the cables, 3-4 in before the plug, made them fail. My cables were all worn and brittle, and GM was right. It was about 4 inches back. I cut about 5 inches back and connected the new plug. Do one line at a time, because the new plugs wires are all white! Yeah, fun! Actually not bad if you do them one at a time. I did do my Camshaft variable timing solenoid plug too at the same time. That is the solenoid that you have to take out the power steering pump, to get it all the way out. Behind the front knock sensor. I am still looking for the plug for the EGR or secondary air injection valve. It is almost identical to the camshaft variable timing solenoid, but the plastic housing has a little specific notch on one side. Not important yet, but would like to have it for the future.

**Edit- Here is the part number for my brake booster check valve.
ACDelco 179-1266
I looked it up on rockauto first.

Would anyone happen to have a guide that tells the part numbers for all the plugs?

 

[AzTruckGuy]

I have been chasing the lack of acceleration and sluggish I6 for way too long. The issue is a vacuum leak, that no one has seem to of found. I have seriously replaced everything on my TB '04. Never could find the secret vacuum leak. Well I found it and yall will not believe it, but I think your gonna love me. I tested the entire side of the engine. NO vacuum leaks. I tested the brake booster. it held at 20-21 psi (I think that's right, from memory) Never did I test the brake booster check valve. Why would I? We its a very cheap part, so I changed it. My TB runs like a champ. For over 2 weeks now, I have not had any power issues or stumble. All power and acceleration has come back and she runs like she is new. Even brakes and stops like it was new. The reason for the brake booster check valve causing the vacuum leak is this. It is supposed to be a one way valve. It holds the pressure for your brake booster but the valve can get weak or fail. So it either wont seal or stays sealed or open. I don't know what mine was doing, but it sure was not doing its job. I LOVE my TB again. I really hope that I help someone. I could not keep this to myself. I know how many people are out there that have lost their mind over this loss of acceleration and sluggish, junk. I know that a brake booster check valve sounds crazy, but its @ $11-$20 on amazon. Its insanely easy to swap out. No reason not to give it a shot. I seriously was about to take my TB into the transmission shop because it wasn't shifting right or stopping right. I also already have a new brake booster and master cylinder, ready to go, but this little valve solved SO SO many issues.

So if its meant for the brakes, how does this affect the acceleration on the Trailblazer?

Im on my 4th cat. Mine was not a cat issue. But when you run rich too long you will destroy them. Just FYI. I have a new super50 muffler and magnaflow cat. Resonator is GONE!!! 3 inch in and out. Don't let people lie and say you will lose power on the back pressure. Its an all in you head myth. The check valve was a leak, and I have put a new one on a few friends GM and chevy and they have noticed a performance boost. Im not saying that this is everyones problem. I have almost rebuilt my entire TB. Almost everything inside of it is new. I did replace the throttle body harness and the camshaft variable timing solenoid, power plug too. I had issues where I would get all my power, then after a turn or a bump, it would lose that "pep". So I changed out the throttle body harness, due to the recalls I saw on them. Chevy never actually admitted the flaw in our throttle body harness, but they did on the tahoes. They didn't run enough cable and the last 3-4 inches of cable, to the plug, were put under so much stress and heat, that the cables fail. GM states that the stress on the cables, 3-4 in before the plug, made them fail. My cables were all worn and brittle, and GM was right. It was about 4 inches back. I cut about 5 inches back and connected the new plug. Do one line at a time, because the new plugs wires are all white! Yeah, fun! Actually not bad if you do them one at a time. I did do my Camshaft variable timing solenoid plug too at the same time. That is the solenoid that you have to take out the power steering pump, to get it all the way out. Behind the front knock sensor. I am still looking for the plug for the EGR or secondary air injection valve. It is almost identical to the camshaft variable timing solenoid, but the plastic housing has a little specific notch on one side. Not important yet, but would like to have it for the future.

**Edit- Here is the part number for my brake booster check valve.
ACDelco 179-1266
I looked it up on rockauto first.

Would anyone happen to have a guide that tells the part numbers for all the plugs?

Maybe Camshaft variable timing solenoid plug is the reason the Trailblazer runs better now?

 

[forrestnummy]

Brake booster check valve, ties into the intake man. Ever seafoamed your car? The plug on the VST, was changed out about a months difference, between the brake booster check valve. I still had power to the VST, I just wanted to change the plug. Ive changed out the VST, 2x, since Ive owned the TB. I knew the plug had oil leak into it before, from the failed VSTs. I had cleaned it, but wanted to replace with new.

 

[AzTruckGuy]

Brake booster check valve, ties into the intake man. Ever seafoamed your car? The plug on the VST, was changed out about a months difference, between the brake booster check valve. I still had power to the VST, I just wanted to change the plug. Ive changed out the VST, 2x, since Ive owned the TB. I knew the plug had oil leak into it before, from the failed VSTs. I had cleaned it, but wanted to replace with new.

I sea-foamed a 2009 Maxima I use to own, to be honest it didn't do anything that improved the Maxima

 

[AzTruckGuy]

Does anyone know the PSI for the Brake Booster check valve? Seems I made the mistake of not having a hand-held vacuum pump, should ressure should be between 15 to 20 hg?

 

[forrestnummy]

In theory it should hold the same if not more than the brake booster. I think. So @ 20. Is correct. It's a one way valve. One way, going into the intake manifold.

 

[JarrettK]

I had some similar issues with my 07 TB, 70K miles on it. I hadn't noticed but my thermostat was out, not sure for how long because I don't drive it that much. Short trips to work and back, or long trips with the camper behind it where the temp gauge looked about right. If your temp gauge isn't pegged straight up and staying there after it is warmed up, change out the thermostat. This isn't saying this is the OP's issue, but others that find their way here for the vague loss of power issues. Also clean out the throttle body. Those two things brought me back to what it used to be. I'm going to check my brake booster check valve next though if this doesn't stick.
Here's a good step by step on the thermostat change.
https://gmtnation.com/forums/threads/alternator-and-thermostat-replacement-how-to.12720/