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Author Topic: Symptoms of a knackered MAF sensor  (Read 16319 times)

northyracing

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Symptoms of a knackered MAF sensor
« on: February 25, 2013, 05:58:39 pm »
As title says really anyone know the tell tell signs if it is knackered as I am getting a judder when car is idleing but don't know if its the PCV

Saintsteve

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Re: Symptoms of a knackered MAF sensor
« Reply #1 on: February 25, 2013, 06:01:55 pm »
Can you hear a hissing sound when you shut the engine down from the PCV valve itself?

There is a small drilling in the PCV housing and if the valve is knackered then the air from inside hisses out.

I would just disconnect the MAF, and see if the engine runs smooth.
If it runs smooth the MAF is generally ok.

northyracing

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Re: Symptoms of a knackered MAF sensor
« Reply #2 on: February 25, 2013, 06:38:41 pm »
I have not really hear a hissing noise just I gets a lumpy idle and then once movin the car is fine so basically start the car up and unplug sensor and if it still runs smooth then it's ok

northyracing

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Re: Symptoms of a knackered MAF sensor
« Reply #3 on: February 25, 2013, 07:23:33 pm »
Just unplugged maf and runs smooth

Offline bacillus

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Re: Symptoms of a knackered MAF sensor
« Reply #4 on: February 25, 2013, 07:56:12 pm »
Just unplugged maf and runs smooth

Sounds like you need another maf.
Without traction power is nothing!

northyracing

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Re: Symptoms of a knackered MAF sensor
« Reply #5 on: February 25, 2013, 11:00:51 pm »
i drove the car for a while got it nice and warm and it started running lumpy on idle unplugged maf and for a second engine revs dropped then back to normal and it still ran slightly lumpy at idle but noticed when driving at low speeds it felt very juddery i have replaced the dv valve but noticed one of the allen bolts but have vibrated loose would this cause a problem

Offline ROH ECHT

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Re: Symptoms of a knackered MAF sensor
« Reply #6 on: February 26, 2013, 06:52:54 am »
The only real way I know of to test the maf is to log data for the intake air mass, group 002 w/vcds, and check that with your known hp. Other than that, you can temporarily swap in a buddy's to see if it solves your issue. Your intake air mass in g/s divided by 0.80 should equal your wheel hp. For example: my air mass is 280 g/s....280/0.8=350 hp


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Re: Symptoms of a knackered MAF sensor
« Reply #7 on: February 26, 2013, 07:03:39 am »
i drove the car for a while got it nice and warm and it started running lumpy on idle unplugged maf and for a second engine revs dropped then back to normal and it still ran slightly lumpy at idle but noticed when driving at low speeds it felt very juddery i have replaced the dv valve but noticed one of the allen bolts but have vibrated loose would this cause a problem
Yes. It will run rough if the loose bolt creates a break in the seal.
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northyracing

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Re: Symptoms of a knackered MAF sensor
« Reply #8 on: February 26, 2013, 06:02:58 pm »
Been havin idle problems and juddery feeling so checked my pcv today I done the blow down the pipe test. I took it off inlet manifold side and blew down the pipe and took oil cap off and you could hear that I was blowing straight through the pcv into the engine also noticed the pipe had quite abit of engine oil in it would this suggest the pcv is naffed

Saintsteve

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Re: Symptoms of a knackered MAF sensor
« Reply #9 on: February 26, 2013, 07:26:09 pm »
If You Can blow and Suck down that Value then it is Faulty. :happy2:

northyracing

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Re: Symptoms of a knackered MAF sensor
« Reply #10 on: February 26, 2013, 07:29:33 pm »
I had abit of oil in the pipes and also when I changed dv it was full of oil surely this ain't right either

Saintsteve

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Re: Symptoms of a knackered MAF sensor
« Reply #11 on: February 26, 2013, 07:32:54 pm »
I had abit of oil in the pipes and also when I changed dv it was full of oil surely this ain't right either

Being full or having signs of oil in it doesnt mean its faulty.As I said if you can blow and suck, the valve inside the pcv is faulty.It has a ball valve inside.

northyracing

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Re: Symptoms of a knackered MAF sensor
« Reply #12 on: February 26, 2013, 07:45:59 pm »
Well put it this way I had a mate blow down the pipe and I had my ear to the oil filler cap and you could hear it inside the engine so he was basically blowing straight through the pcv

Offline DarkSideJohn

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Re: Symptoms of a knackered MAF sensor
« Reply #13 on: February 26, 2013, 07:51:31 pm »
Not to go off topic or steal ;)
Can this effect dirty diesels too ? I have a rough idle of my 2.0 TDI, its not constant or regular , just every now and then
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northyracing

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Re: Symptoms of a knackered MAF sensor
« Reply #14 on: February 27, 2013, 06:41:09 pm »
If You Can blow and Suck down that Value then it is Faulty. :happy2:
I just tried my pcv again and can blow and suck down the pipe with ease