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Engine sputters when going down the road like it's running…

Customer Question
Engine sputters when going...

Engine sputters when going down the road like it's running out of gas, then clears up and runs fine for days.

Mechanic's Assistant: Has the vehicle turned into a gas hog? And how does it start -- same as usual?

Stars good, have not noticed a difference is gas hog. seems to act up more when I drive at high altitude. In Florida it runs fine, in Montana it runs awful.

Mechanic's Assistant: What year is your Montana?

Its a Trailblazer, I drove it in Montana, 2003

Mechanic's Assistant: Are you fixing your Montana yourself? What have you tried so far?

Fuel filter, map sensor, yes myself.

Submitted: 9 months ago.Category: Chevy
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Answered in 1 minute by:
9/20/2017
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago
AMEDEE
AMEDEE, CHEVY TECHNICIAN
Category: Chevy
Satisfied Customers: 28,000
Experience: ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
Verified

Hello and welcome!

My name isCustomerand I can assist you with your question.

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

I am very sorry your having this issue with your vehicle.

I will try my best to answer all of your questions.

However, before we get started, please let me mention a few things.

1. If at any point you would like to speak on the phone, please feel free to request a phone call on your end and I can call you right away.

2. If you dont understand any technical terms or anything that I mention (component tests or theory or operation), please let me know and I will provide you with a more in debt explanation or answer.

3. Please understand that I am here to help.

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Is the check engine light on?

Are there any codes in the computer?

Would you be willing to speak on the phone?

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Customer reply replied 9 months ago
engine light is on, but it is always on, yes I can speak on the phone.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Hello!

Just so you're aware, phone calls are extra. If you would still like to speak on the phone, please request a phone call on your end and I will call you right away.

Otherwise, we can continue on this page.

Please let me know which direction you would like to go in so we can continue.

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Customer reply replied 9 months ago
I would like to just email.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Ok, no problem.

May I start by getting your VIN, any stored codes in the computer and a list of everything that has been replaced for this issue?

Thank you!

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Customer reply replied 9 months ago
1gndt13sx32113465 I am not able to read the codes now.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Thank you for that information.

So would you like me to list some possible causes for you?

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Customer reply replied 9 months ago
p0420 po172 o0420
Customer reply replied 9 months ago
I dont know how old the codes are, it seems no one can clear them once the issue is fixed.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Thank you for that information.

The P0172 is a rich code. This tells you the engine is running rich.

The P0420 code is a converter code. This is telling you the computer has detected that the converter is not working properly.

The only thing you need to be concerned about now is the rich code. I would not worry about the P0420 converter code at this point causing this sputtering condition unless of course the converter is plugged.. and if thats the case, it needs to be replaced.

The P0172 rich code is a fuel trim code which can be triggered by several things. First, check the fuel pressure and ensure that the fuel pressure is within specs and it does not leak down. If so, check the fuel pump and fuel pressure regulator for leaks.

Also, check for air/vacuum leaks as well as the engine vacuum.

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Customer reply replied 9 months ago
The puzzle her is that the problem does not occur on a regular basis. I have replaced the fuel filter and map sensor. it seems to be worse at high altitude 4000 or higher. I live in Florida and it seems fine ther but when I travel it acts up. This has been happining for over a year now.
Customer reply replied 9 months ago
is there a way I can clear the old codes myself?
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

YES, you certainly can clear the codes. You have a few options.

Either use a hand-held scanner or you can disconnect the battery cables from the battery

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

I am glad I can help!

Please don't forget to honor your good faith deposit by rating my answer as "5 STARS or SMILEY FACES" for assisting you today.

Keep in mind, we can still continue this conversation at no further cost to you even after you rate my answer. Just reply back to me using this page and I will get it and get back to you ASAP!

I just ask that you allow time in between replies as I may be helping other customers or off line spending time with the family.

Also, if you are a member or if you have a subscription to the site, you still need to rate my answer in order for me to get credit for assisting you with your question.

You should see the rating system towards the top of the page.

Please let me know if you have any further questions.

Thanks and have a great day!!

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Do you have any further questions?

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Customer reply replied 9 months ago
I will disconect the battery and respond with the next engine code.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago
Sounds good sir
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Customer reply replied 9 months ago
I disconected the battery and the vehicle is still acting like it's out of gas, but it will not set a code.
Customer reply replied 9 months ago
I think the old code of running rich may be due to it sputtering and then getting fuel again? What do you think about the fuel pressure regulator?
Customer reply replied 9 months ago
I do not think it is a restriction of fuel, when I step on the pedal and it shifts down it runs better, which should be demanding more fuel since the r.p.m. went up when it shifted down.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Hello and sorry for the delay sir.

YES, that is correct. Again, it could be a faulty fuel pressure regulator.

YES the old code is likely due to it sputtering. This indicates a fuel issue. Too much or too little fuel.

I would agree. I dont think it is TOO LITTLE fuel. The P0172 code indicates RICH which means TOO MUCH FUEL.

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Customer reply replied 9 months ago
Also at times the idle runs high around 900, even after the engine is warm.
Customer reply replied 9 months ago
When I unplug the vacum to the fuel pressure regulator there is no vacum noticed, should there be?
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

That could very well be related.

Faulty, dirty throttle body or an air/vacuum leak.

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Customer reply replied 9 months ago
I'll take a look thanks.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Your welcome!

I am glad I can help!

Please don't forget to honor your good faith deposit by rating my answer as "5 STARS or SMILEY FACES" for assisting you today.

Keep in mind, we can still continue this conversation at no further cost to you even after you rate my answer. Just reply back to me using this page and I will get it and get back to you ASAP!

I just ask that you allow time in between replies as I may be helping other customers or off line spending time with the family.

Also, if you are a member or if you have a subscription to the site, you still need to rate my answer in order for me to get credit for assisting you with your question.

You should see the rating system towards the top of the page.

Please let me know if you have any further questions.

Thanks and have a great day!!

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Do you have any further questions, sir?

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Customer reply replied 9 months ago
When I unplug the vacum line from the fuel pressure regulator there is no vacum from the line, shouldn't there be?
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

YES, there should be engine vacuum there only with the engine at idle though..

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Customer reply replied 9 months ago
What would cause a lack of vacum then?
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Plugged or loose vacuum line

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Customer reply replied 9 months ago
OK I'll take a look at that then
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Sounds good!

I am glad I can help!Please don't forget to honor your good faith deposit by rating my answer as "5 STARS or SMILEY FACES" for assisting you today.Keep in mind, we can still continue this conversation at no further cost to you even after you rate my answer. Just reply back to me using this page and I will get it and get back to you ASAP!I just ask that you allow time in between replies as I may be helping other customers or off line spending time with the family.Also, if you are a member or if you have a subscription to the site, you still need to rate my answer in order for me to get credit for assisting you with your question.You should see the rating system towards the top of the page.Please let me know if you have any further questions.Thanks and have a great day!!
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Customer reply replied 9 months ago
The hose has no restrictions and there is no vacum at the resonator?
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

It should come from the intake manifold.

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Customer reply replied 9 months ago
I can find no vacum where the hose connects to the plastic box on top of the engine, I thought it was called a resonator?
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

NO sir. It is not.

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Customer reply replied 9 months ago
I pushed a plastic brush tip into the hose conection and found no blockage there.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Does it have vacuum coming out of the intake?

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Customer reply replied 9 months ago
this is a 4.2 the box the hose goes to has no vacum there.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Can you send me a few pics and or a video along with your VIN?

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Customer reply replied 9 months ago
My Chilton manual refers it as the air intake resonator that the vacum line connects to the fuel pressure regulator.
Customer reply replied 9 months ago
That is it, but I can feel no suction where the hose connects.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Then maybe there is a leak on the air intake/chamber or "resonator" If so, it may need to be replaced.

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Customer reply replied 9 months ago
OK I will take a look at that.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Sounds good! Your welcome!

Please dont forget to rate!

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Do you have any further questions, sir?

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Customer reply replied 9 months ago
I will look at the intake tomorrow and see what I can find out.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 9 months ago

Sounds good!

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 8 months ago

Hello there!

I am just checking in to see how things are going and to see if you need any further assistance?

If so, please let me know as I will be happy to help.

Best Regards,

Customer/p>

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Customer reply replied 8 months ago
I have visitation with my daughters the next few days and will resume working on my issue after that.
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 8 months ago

Sounds good thanks for the heads up!

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