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2002 chevy trailblazer_ltz
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Discussion Starter #1
Over the past month I have had an issue with my 2002 Trailblazer stalling.

2002 Trailblazer (teenage daughter vehicle) Owned by me (dad) since 2003.

Stalling when cold, seems like isn't getting enough gas. Takes a few minutes , then it runs better but still feels like its not running smooth.
Since I have owned it I noticed it goes into a " Low Power" mode until it reaches a certain temperature then it kicks into regular power running mode.

Here is what I did and what I have tried (So Far)
2018 Replaced Fuel Filter.
Replaced Camshaft Cam Shaft Position Sensor

This must of worked on what ever was happening at that time , but do not remember what the issue was.

2019 (few days ago)
Oil Change.
Throttle body clean
Camshaft Actuator Solenoid Valve Change

Its running better but still feels sluggish. When driving today it had low power then regular power, then back to low power. Never was close to stalling.

Future replacements.
Engine Coolant Temperature Sensor
Possible Replaced Camshaft Cam Shaft Position Sensor

If anyone else has suggestions on what is going on with vehicle, that would be great. And hopefully I can prevent my daughter from hitting another Tree
 

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2004 chevy trailblazer_lt
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I would check your fuel pressure and test the operation of the fuel pressure regulator to see if perhaps your fuel pump is weak or if the fuel pressure regulator is leaking.
 

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Discussion Starter #3
I would check your fuel pressure and test the operation of the fuel pressure regulator to see if perhaps your fuel pump is weak or if the fuel pressure regulator is leaking.
I have considered that , and making fuel pump my last resort.

Is there an easy way to test fuel pump?

I hate to take the entire tank down to test.

Also looking at cost of a fuel pump. see they range 50 or more.
Would an aftermarket be ok ?

Thank you,
 

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The first thing you need to do is get a fuel pressure tester. You can either buy one or rent one from Advance Auto Parts, AutoZone or O'Reilly Auto Parts.

If you do not have one, a Haynes repair manual for the TrailBlazer/Envoy is a good investment. It will walk you through various diagnostic tests like pressure testing a fuel pump.

For your TrailBlazer, the fuel pressure test port is located next to the fuel filter. Remove the protective cap, screw the fuel pressure tester onto the port, turn the ignition key to the run position and see what the fuel pressure is WITHOUT the engine running and note the pressure. Then start the engine and see what the fuel pressure is WITH the engine running and note that pressure. Finally, while the engine is running, remove the vacuum line from the fuel pressure regulator and see and note if the fuel pressure increases, decreases or stays the same. If the pressure goes up, your fuel pressure regulator is functioning properly.

Compare the fuel pressure values you measured to what is specified in a Haynes manual, a factory service manual or to an online source like Alldatadiy. If the pressures are normal, then you are likely not having an issue with the fuel pump and fuel pressure regulator. If the fuel pressure values are lower than spec, you are likely looking at a fuel pump problem.

Regarding replacement fuel pumps, do not cheap out on them if you only want to replace it once. Get either an ACDelco or a Delphi fuel pump. They can be ordered from either RockAuto or Amazon.com and cost significantly less than a local parts store. I would stay away from the no-name, white box, low cost fuel pumps because of all the work involved in replacing the fuel pump.

Good Luck!
 

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Discussion Starter #5
I tried 3 testers from a parts store, and brought 2 different testers from another store.
Cannot get any of them to work right.
Some had the wrong adapters and some were just broken.

If I buy a tester is there a good suggestion on one?
 

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Discussion Starter #7
Thanks that helps.

Replaced cam shaft possition sensor and even though it is running better, its throwing a code.

Have to check the code , but is this normal when replacing sensor?
 

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You are welcome.

I do not know if throwing a code after replacing the cam position sensor is normal (I would assume it is not). When I replaced my cam position sensor (due to my breaking it when doing some other work) on my TrailBlazer, it did not throw a code.

What is the code you are getting now?
 

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Discussion Starter #9
It is Error P0340.
Didn't happen until I changed the sensor, I did not put the old one back in yet.
Cleared the code today , going to drive tomorrow and see if it comes back.

I also ordered a fuel pump, cost wise it was 1/4 the cost of actually checking the fuel pump.

At times it runs good at times it runs like its dying.
So pointing more and more towards fuel pump

Plus I am running out of things to replace.
 

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The P0340 code is for a camshaft position sensor circuit malfunction. Since you just replaced the sensor, I would check the plug to make sure it is seated properly and that there are no wires that came undone from the connector before assuming that the new sensor is bad.

Don't forget to check the fuel pressure regulator - it could have a bad diaphram.

Forgive me, but I don' see how a fuel pump assembly, even a no-name white box cheapie, can cost 1/4 the price of an under $50 fuel pump pressure tester.

Considering this is for your daughter's TrailBlazer, don't cheap put on a vital and difficult to replace part like a fuel pump. Go with either and ACDelco OEM pump or a Delphi pump (which could very well be an OEM part). I am all for using quality aftermarket parts in order to save a few $$ from companies with good reputations, but when it comes to fuel pumps that reside in the fuel tank, an OEM or OEM-equivalent is the only way to go.
 

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Discussion Starter #11
The AC delco MU1837 is 170$
Fuel pressure tester that you showed for an example is 40$
That is where I am getting 1/4 cost.

I will check the connection and go from there.

Thanks for the continuing help.
 

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Discussion Starter #12
I have ordered a fuel pressure testing kit, that should work to test out pressure.
If not I will look at others.
Reseated camshaft position sensor. Driving it tommorow and will test.
I have developed a leak of some kind that may be from oil filter. Going to scope it tommorow. (Frustration).
When I test pressure will post results.
 

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Cam Shaft position sensor

I have been battling the P0340 code for several months. Had stalling when going from highway speed to low speed. Changed cam shaft positioning sensor. Problem went away but still got the code. I cleaned the connectors. I reseated the sensor. I check the voltage in the wires. I bought a new OEM sensor. Still got P0340 code. Did a lot of research. I was also experiencing an intermittent loss of all display gauges. The suggestion was to change the ignition switch to fix the dash problem. My research also found that many computer signals go through the ignition switch. Well, today I changed the ignition switch. Took a total of 5 minutes. Eureka! The P0340 code is fixed.
 

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Discussion Starter #14
It was fixed after replacing it back with the old one,
Was a troubleshooting step of the real problem with the stalling and poor performance.

Thanks for the advice with the code. I will definitely use that advice if I run into the issue again.

The oil leak was from a filter that was not tight (I hope) still testing.

Currently I have all parts to replace everything, just waiting on testing the fuel pressure and then I will post results.
 

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Discussion Starter #15
Recieved fuel pressure tester, worked on some body rust, dropped oil again, here is what I have..

Oil filter had a small indentation in the o-ring that didn't provide a proper seal.
So replaced oil filter and oil re-used. It was all good

Fuel Pressure test,

When starting it went to 54 (normal) then dropped to 47 when running.

I have a few pressure regulator, thinking that may be it, unless someone else has a suggestion.
 

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Discussion Starter #16
Final update
After driving it around for 3 days I concluded that it was the Fuel Pressure Regulator and not the fuel pump.
Now its back to " normal".
Thank you for the help getting me on track and the advice.
 

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Discussion Starter #18
Revisited!
After a week of running Trailblazer , its started stalling again. And had issues starting one of the days.
I replaced the fuel filter to make sure that was at least troubleshooted. And it did not make a difference.

Now I am stuck with unknown stalling issues again...
Rechecked the fuel pressure, It shows 53 when initializing ignition then drops to around ~43 when running.

I did not try the battery disconnect again. ( this is the only thing I can think of atm)

Any more suggestions would be great.!
 
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