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Old February 8th, 2018, 13:05   #1
Shonky
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Default Maf or something else

Hi, I've just bought a 2005 golf plus 1.9tdi, all was well until it started running rough and smoking.I pulled the plug from the maf sensor and it started running fine again.I fitted a new sensor, plugged it in and it's running rough again. I was thinking maybe it's the wiring but I don't know what the voltage etc should be, or could it be something else, if anyone has any ideas id be grateful.
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Old February 8th, 2018, 13:18   #2
UhOh
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Guessing will eventually get tiresome.

Have it scanned.

BTW - Anything other than a quality MAF (Bosch) is going to be questionable. Because MAFs play a pretty important part in how things operate they're not something to cheap out on.
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Old February 8th, 2018, 13:21   #3
Mongler98
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what part brand did you get? OEM? ebay? autocrap stores? amazon?
if you unplug it and it runs fine, thats your issue. you probably have a bad unit, RMA that suker and get a quality one and or try and repair/clean the old one? MAF's are simple circuit and when they get dirty they dont work. not sure why you would have much smoke increase with a bad maf? it usually sends into limp mode or just rough ride. you have a tune on it or larger injection? stock?
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Old February 8th, 2018, 13:36   #4
Shonky
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Scanned it, no codes(except a glow plug earth). Doesn't go into limp mode. Obviously get check light when the sensor is disconnected. Doesn't smoke all the time, just random clouds. Admittedly the new sensor was from Gsf but is behaving exactly the same as the Bosch. Wasn't sure what to do next, thought I'd get some advice before I start throwing money at it. Cheers

Last edited by Shonky; February 8th, 2018 at 13:38.
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Old February 8th, 2018, 13:39   #5
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Quote:
Originally Posted by Mongler98 View Post
not sure why you would have much smoke increase with a bad maf? it usually sends into limp mode or just rough ride. you have a tune on it or larger injection? stock?
There's different ways in which a MAF can be "bad." 1) Outright failure (I've experienced this- turned the car into a bucking bronco- don't recall there being a code popping up [I run UltraGauges in all my cars]); 2) Degraded- FE and performance will drop (over time; very subtle); 3) Improper readings from a cheap MAF (readings within spec, but output isn't correct for actual conditions).

Could be that the MAF is reporting more air flow than is happening, in which case the ECU is happy about commanding more fuel. More fuel and not enough air = black smoke.

I'd unplug the new MAF and drive for a while. If it behaves (no black smoke) then it's for sure the MAF and or MAF circuit. If it's a cheap MAF then replace it with a quality one, regardless.
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Old February 8th, 2018, 14:52   #6
Shonky
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Cheers uhoh, when it's unplugged it drives fine, maybe a little thirsty.

Last edited by Shonky; February 9th, 2018 at 07:46.
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