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what causes the engine to pulse

Customer Question
what causes the engine to pulse
Submitted: 5 years ago.Category: Chevy
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Answered in 1 minute by:
12/30/2011
Chevy Mechanic: Pete, Auto Service Technician replied 5 years ago
Pete
Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 29,516
Experience: 14 years GM dealer Technician.
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Hello,I will be glad to try and assist you with this,Welcome to Just Answer.

Hi.

I just need a little more info to assist better.

Is the idle going up and down or does it feel like it has a misfire at idle or when driving?

Let me know so we can continue,Thanks Pete!
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Customer reply replied 5 years ago
idle up and down pulses when going up a hill or under power when taking off
Chevy Mechanic: Pete, Auto Service Technician replied 5 years ago
O.k.

This can usually be caused by a vacuum leak on the engine which can cause the idle to fluctuate like this here.

I would check over the engine to see if any vacuum leaks are found visibly and repair any that are found.If none are found then a shop or dealer can inject smoke into the intake and where the smoke leaks out is the location of the vacuum leak that needs repaired.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Happy Holidays!
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Customer reply replied 5 years ago
when looking for a leak there are very few vacuum lines nothing look wrong when the eng light was on and read one of the codes said possible manifold sensor no thought about clogged cat conv ? possible
Chevy Mechanic: Pete, Auto Service Technician replied 5 years ago
It can be a plugged catalytic converter but usually if this is the case the engine would have a lack of power and very slow to accelerate.

Even though you have a few vacuum lines there may be a leak around where the upper intake seals on the lower intake or around the electrical connection for the injector unit or the leak can be where the lower intake seals around the cylinder heads and engine block.This is where a smoke test helps to aid in locating the area of the leak so it can be repaired.

An exhaust back pressure test would show a plugged converter,this can be done by most shops and or dealers or an exhaust shop.The exhaust back pressure shouldn't exceed 1.5 psi through any rpm range.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Happy Holidays!
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Customer reply replied 5 years ago
the engine does have a lack of power and is slow to accelerate then normal before
Chevy Mechanic: Pete, Auto Service Technician replied 5 years ago
O.k,

This can be caused by a plugged catalytic converter,The exhaust back pressure needs checked to see if it is the cause as well as fuel pressure to see if it is low or if you have a restricted fuel filter as the fuel filter needs replaced once a year or every 15,000 miles.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Happy Holidays!
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Customer reply replied 5 years ago
fuel pump in tank as replace about 2 yrs ago the fuel filter has not been replaced sence i bought it had 69,000 now it has 164+,000
Chevy Mechanic: Pete, Auto Service Technician replied 5 years ago
Your fuel filter definitely needs replaced and this could be the cause as usually these start to restrict after 1 year and if it has this many miles on it since it was replaced last it is a definite possibility.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Happy Holidays!
Pete
Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 29,516
Experience: 14 years GM dealer Technician.
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Pete and 87 other Chevy Specialists are ready to help you
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Customer reply replied 5 years ago
At least it confirms my thoughts and i am no expert but gives me good place to start, then back presure checked as well as smoke check

thank you
Chevy Mechanic: Pete, Auto Service Technician replied 5 years ago
Your welcome.

Thanks Pete!
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Pete
Pete
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