Chevy

Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP

Ask an Expert,
Get an Answer ASAP!

Chevy
This answer was rated:

2003 Chevy: accelerate..check engine light came..Mass Air Flow

My 2003 Chevy Avalanche with...
My 2003 Chevy Avalanche with 135K miles on it start running rough yesterday. It does ok at low RPM and low speeds, but struggles when you try to accelerate. The check engine light came on and AutoZone said it was the Mass Air Flow sensor. I used a MAF cleaner on the old one, it didn't work. I installed a new MAF, still didn't fix the problem. Still running rough. What do you think it is?
Show More
Show Less
Ask Your Own Chevy Question
Answered in 40 minutes by:
11/14/2010
Bill
Bill, Chevy Technician
Category: Chevy
Satisfied Customers: 1,776
Experience: GM Certified Master Technician
Verified

Welcome to Just Answer.com. I'm here to help you and your 100% satisfaction is my goal. Please Accept if you are satisfied.

Hello,

This is very likely a restricted catalytic converter. What happens is the restriction in the exhaust causes incorrect airflow through the engine. The air can't come in because it can't get out of the exhaust. Therefore the readings the mass airflow "should" see related to engine vacuum, rpm and load are slewed off from where they should be. This often shows up as a mass airflow sensor fault code even though the restriction is in the exhaust. A test with an exhaust backpressure gauge will confirm this. I've seen some techs temporarily remove the oxygen sensor and drive it (albeit very noisy) to see if there is a difference in power. Based on your description I'm as confident as I can be from my chair that a restriction in the cat is your problem. I would suggest however confirming it either way suggested above as they can be a bit expensive and we want to be sure. :)

Cheers

Bill

Ask Your Own Chevy Question
Customer reply replied 7 years ago
Thank you for your help and advice. Why do you think this problem came on so quick? Seems to me a restriction in the Cat would build up over time. Also, I'm not afraid to take on some repairs. Is this a repair that a mechanically inclined homeowner can accomplish, or should I take it to a shop? How many hours does Mitchell or AllData call for it, and does it require any welding?

It often happens that way. There may be a partial restriction for a while but eventually it just gets to the point where it affects engine operation. Generally you're looking at an hour and a half or so plus any diagnostic charges or broken bolt charges. Again... I strongly suspect that's your problem but please do confirm it with the backpressure test or the other way. Replacement of the cat at home is not always the easiest thing to do for two reasons. One is the angle it needs to be moved to in addition to moving the trans crossmember is all but impossible on the ground. Secondly is the nuts/studs that hold the converter onto the manifold quite often are frozen on and may require some creative measures to get them off... sometimes air chisels... torches, etc.

Ask Your Own Chevy Question
Customer reply replied 7 years ago
Understood, I will enlist the help of an expert. I may however try your described testing method of removing the oxygen sensor to confirm the problem. Considering this may not get fixed today, how do I reply when the problem is fixed to confirm your suggestion was correct, and give you positive online feedback?

You merely log in here and click on your questions. I'll be here. :)

Bill

Bill
Bill, Chevy Technician
Category: Chevy
Satisfied Customers: 1,776
Experience: GM Certified Master Technician
Verified
Bill and 87 other Chevy Specialists are ready to help you
Ask your own question now
Ask Bill Your Own Question
Bill
Bill
Bill, Chevy Technician
Category: Chevy
Satisfied Customers: 1,776
1,776 Satisfied Customers
Experience: GM Certified Master Technician

Bill is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money.

Todd LRochester NY

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

< Previous | Next >

Meet the Experts:

GM Tech (Cam)

GM Tech (Cam)

Chevy Technician

15,289 satisfied customers

GM Grand Master Technician 2007. 14 years experience.

Gary

Gary

Chevy Technician

9,357 satisfied customers

15 years GM master tech

Tim&#039;s Auto Repair

Tim's Auto Repair

mechanic

8,866 satisfied customers

Have owned a repair shop for 25 yrs.

Dave Nova

Dave Nova

Chevrolet Technician

7,092 satisfied customers

ASE Master Certification. GM World Class Certification

John

John

Master A.S.E Automotive technician

4,071 satisfied customers

A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician

Don - Mo Lurch

Don - Mo Lurch

Auto Mech / Electronics

2,918 satisfied customers

Chevrolet Cert., Heavy Line Mech, Race Shop Owner, Mobile Electronics.

Ron Z.

Ron Z.

- Chevy Tech -

2,734 satisfied customers

18+yrs experience. State Inspector and Chevy Diagnostics

< Previous | Next >

Related Chevy Questions
Exhaust fluid light 2011 gmc minus 9 degrees this morning
exhaust fluid light 2011 gmc minus 9 degrees this morning does this freeze … read more
Eric
Eric
Retired
N/A
14,436 satisfied customers
Same issue, as on this screen. 2011 duramax, service exhaust
same issue, as on this screen. 2011 duramax, service exhaust system - see owners manual. Have snap on code reader, no error codes present. 162k miles.… read more
Eric
Eric
Retired
N/A
14,436 satisfied customers
Fuel coming out exhaust. Turned into a gas hog. Chevy half
they changed plugs plug wires injectors and the truck runs rough and mileage is down and holding your hand at the exhaust you can feel droplet of unburent fuel … read more
Expert
Expert
15 satisfied customers
My engine light went on yesterday The code is P0013. Exhaust
My engine light went on yesterday The code is P0013 … read more
fordguy4u
fordguy4u
Automotive Tech
Vocational, Technical or Trade Scho
70 satisfied customers
Engine light on" clean exhaust filter continue to dric. Ve
engine light on " clean exhaust filter continue to dric … read more
BOBBYSS
BOBBYSS
TECHNICIAN/ADVISOR
Associate Degree
8,343 satisfied customers
I get a bad odor like rich exhaust from the car. No exhaust
I get a bad odor like rich exhaust from the car. No exhaust leaks, no check engine light all engine data seems normal … read more
rpmdiag
rpmdiag
High school
7,267 satisfied customers
My catalytic converter went on my 2008 Impala I think
My catalytic converter went on my 2008 Impala I think because I had a wiring problem that made the fuse blow that controlled the circuit for the O2 sensors. Also I had a AIR valve that was stuck in th… read more
Chris (aka - Moose)
Chris (aka - Moose)
Vocational, Technical or Trade Scho
108 satisfied customers
My catalytic converter failed a couple of years ago. I think
My catalytic converter failed a couple of years ago. I think it was a combination of a stuck AIR valve and a wiring problem that kept causing the fuse that controls both O2 sensors and the EVAP soleno… read more
fordguy4u
fordguy4u
Automotive Tech
Vocational, Technical or Trade Scho
70 satisfied customers
Where is the Exhaust Cam Position Actuator Solenoid located
Where is the Exhaust Cam Position Actuator Solenoid located on 93 GMC Serra Trunk ? … read more
Joecamel90
Joecamel90
Technician
Associate Degree
24 satisfied customers
P0420 bank 1. 06 malibu maxx 3.5. Checked for exhaust leaks
Checked for exhaust leaks sprayed around intake looking for vaccume leakes … read more
Ron Z.
Ron Z.
- Chevy Tech -
Vocational, Technical or Trade Scho
2,734 satisfied customers
Exhaust smell with a/c on and windows closed. No it has been
we have mechanics at the factory they checked the exhaust mnaifold and a/c intake but could not pinpoint it we can take it to the dealer if needed … read more
Jerry Newton
Jerry Newton
Vocational, Technical or Trade Scho
2,066 satisfied customers
There is some exhaust fumes getting in the car, 1988 Chevy
Hi, there is some exhaust fumes getting in the car, 1988 Chevy Coup, need a mechanic to fix it… read more
eauto
eauto
self employed
High School or GED
74 satisfied customers
Cleaning exhaust fluid message then goes into engine power
Cleaning exhaust fluid message then goes into engine power reduced. Anything I can do we are in the boonies … read more
Eric
Eric
Retired
N/A
14,436 satisfied customers
2008 Silverado 3500 HD 6.6 question can I do a exhaust
2008 Silverado 3500 HD 6.6 question can I do a exhaust filter delete just the filter I don't want to remove my catalytic converter im in California so I don't want any problems please let me know than… read more
Jerry Newton
Jerry Newton
Vocational, Technical or Trade Scho
2,066 satisfied customers
I Want To Take Out The CATALYTIC CONVERTERS on my 2005 chevy
I Want To Take Out The CATALYTIC CONVERTERS on my 2005 chevy malibu can i disconect the stabilyzer ends and tist it to remove the cat … read more
AMEDEE
AMEDEE
AUTOMOTIVE TECHNICIAN
Vocational, Technical or Trade Scho
9,105 satisfied customers
Pete again, lack of power like a catalytic converter is
Hey Pete again, lack of power like a catalytic converter is stopped up or air filter stopped up, no codes, checked back pressure on pre-cat 02 sensors and after cats, doesnt appear to have stopped up … read more
Pete
Pete
Independent Auto Technician
Vocational, Technical or Trade Scho
138 satisfied customers
Knock sensor on bank 2, catalytic converter on bank 2 codes
knock sensor on bank 2, catalytic converter on bank 2 codes on 4.3 liter 2011express van … read more
Ron Z.
Ron Z.
- Chevy Tech -
Vocational, Technical or Trade Scho
2,734 satisfied customers
The catalytic converter. Is it worth the cost to replace it?
the catalytic converter. Is it worth the cost to replace it? … read more
Ron Z.
Ron Z.
- Chevy Tech -
Vocational, Technical or Trade Scho
2,734 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x