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Anonymous Poster
Nov 9, 2008, 11:22 AM
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mass air flow sensor
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2003 chevy 3500 express van
6.0 vortec engine
125,000 miles
would I get a code for a bad air flow sensor or would I just get the symptoms of having a bad one.
and could one of the symtoms be running lean. I am trying to troubleshoot this problem and this was just a lead I
got. My main problem is truck will start and run fine then check engine light comes on truck will then run rough
(misfires), then the truck will correct itself and run fine again. this will happen through out the day. The truck is running or idling for 5-8 hours a day
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Loren Champlain Sr
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/ Moderator
Nov 9, 2008, 11:32 AM
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Re: mass air flow sensor
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Computers are great, but we can't rely on them 100%. They don't always catch every hiccup. We've fixed many
MAF sensors by just cleaning them. I'm not sure if yours is accessable or not. Are you losing injector pulse when the problem occurs? Yes, a lean or a rich condition can cause your symptoms. It also can get very expensive throwing parts at it, as you probably already know. Sometimes, no most always, it is cheaper in the long run to have a tech diagnose it for you. You can still do the repairs, but...
Loren
SW Washington
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Guest
Anonymous Poster
Nov 9, 2008, 1:54 PM
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Re: mass air flow sensor
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loren,
the problem is my highly paid mechanic seems to be guessing too. Costing me not only parts but labor. Just wanted to know if my map was bad would I get a code for it or just symptom codes?
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Loren Champlain Sr
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Nov 9, 2008, 2:14 PM
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Re: mass air flow sensor
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Generally speaking, you would get a code. If your tech can catch it while it is acting up, he should be able to watch live data on his scanner. Sometimes (and I stress, sometimes) you can tap on the MAF with the plastic handle of a screwdriver and get them to act up (if faulty), but not always. There are so many things that could be causing a problem. Can the tech take it for a drive, maybe with you driving, so he can watch the scan data?
Intermittent problems can be a real nightmare to find. Good luck.
Loren
SW Washington
(This post was edited by landdchamploren on Nov 9, 2008, 2:16 PM)
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Guest
Anonymous Poster
Nov 9, 2008, 2:29 PM
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Re: mass air flow sensor
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Intermitten, I'll say. This is a work truck and is used for a route, It must run everyday. Let it idle for 2 hours trying to get the check engine light on, of course would not come on. Go to work next day 15 minutes in the light pops on. I am loosing my mind.
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Loren Champlain Sr
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Nov 9, 2008, 3:16 PM
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Re: mass air flow sensor
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Ah, don't feel bad. At least you have some brain cells left to lose. Mine's been gone for years. LOL. Have a great Sunday.
Loren
SW Washington
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Jeff Norfolk
Enthusiast
Nov 9, 2008, 4:57 PM
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Re: mass air flow sensor
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There should be some miss fire data in the scan tool if the light is coming on and running bad. I wounder if there is any miss fire codes present when the MAF code is there. MAF code could be a secondary code to the miss fire. At the same time the miss could be a secondary symptom due to the MAF With the miss fire data in the scan tool, you mechanic should be able to see if the miss is cylinder specific or just random. If it is cylinder specific then that really leaves three things that are causing it. Either way the MAF may be tripping a code due to the miss. It may be metering to compensate for the miss and going out of the desired range. Just a side note I have replaced injector #6 a handful of times for this very described problem. Obviously there was a diagnosis involved in these repairs, but #6 none the less each time. 
Jeff
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Guest
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Nov 9, 2008, 11:46 PM
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Re: mass air flow sensor
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You can get a specific failure code for a MAF if it fails out of range but it can also fail within parameters & not set MAF specific codes but other related codes.
I didn't notice any codes in this thread so I'm not sure what you are getting... Some usually within parameter codes you can get are P0171 & P0174 lean bank 1, lean bank 2, but there are alot, alot of things that can set those codes...
Intermittens can be tricky to find. You got some good advise... along with the codes is the freeze frame data that stores when a code sets.... that will tell you the driving conditions when the codes sets & help duplicate the conditions.
sounds like you've already replaced some parts & so hopefully your tech has already check the TSBs & your calibration code of the PCM to make sure it has the most current flash...
I've seen some drivability probs solved with just a simple updated reflash....
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