Bad air/fuel mixture
10-09-2011, 09:51 PM
#1
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Join Date: Mar 2011
Location: Brantford
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Bad air/fuel mixture
A couple of weeks ago my 1998 A4 all of a sudden started to run super rich. It ran similar to when my DV valve blew off, rich, black smoke, wont idle, stalls but this time it is drivable (very short distances).
I have replaced my DV Valve with a stock one, the MAF sensor, a hand full of vacuum lines PCV valve and replaced that J tube and T connections.
I took it to Brantford VW to have a throttle body alignment done but at that point the shop foreman said not to bother as he didn't think that was the problem.
The car idles super rough, stalls and pisses gas out the exhaust along with throwing a MAF code...
I am in need of a suggestion
I have replaced my DV Valve with a stock one, the MAF sensor, a hand full of vacuum lines PCV valve and replaced that J tube and T connections.
I took it to Brantford VW to have a throttle body alignment done but at that point the shop foreman said not to bother as he didn't think that was the problem.
The car idles super rough, stalls and pisses gas out the exhaust along with throwing a MAF code...
I am in need of a suggestion
10-11-2011, 05:54 PM
#2
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Location: toronto
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Re: Bad air/fuel mixture
you have to check the maf sensor reading using a scan tool. im not sure what the g/s spec is on your engine, but lets just say around 3g/s at idle and much much higher at wide open throttle. airl flow should increase proportionate to throttle position, if its showing no response or seems 'inconsistant' when you open the throttle, most likely the sensor is contaminated or gone bad. try unpluging it and see if the engine runs different.
10-11-2011, 10:26 PM
#3
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Re: Bad air/fuel mixture
Unplugging the MAF allows the the engine to stabilize, although under load it will choke out as soon as the motor reaches operating temp. I changed the MAF with a used one I picked up from a friend, and it ran like most cars do when that sensor faults (revs up to 1500 rpm or so, then drops, idles up and drops).
I am still under the assumption that I need to have a TBA, but the tech at VW disagrees.
lets just say, I parked my clean white Impreza behind the a4 and when I was done the front end
of the Subi was Black.
I am still under the assumption that I need to have a TBA, but the tech at VW disagrees.
lets just say, I parked my clean white Impreza behind the a4 and when I was done the front end
of the Subi was Black.
10-11-2011, 10:32 PM
#4
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Re: Bad air/fuel mixture
the only other thing I can think up is my ECU which has an UpSolute chip in it has malfunctioned.
But I checked their forums and things like this only really during or directly after the car is tuned.
But I checked their forums and things like this only really during or directly after the car is tuned.
10-12-2011, 12:17 AM
#5
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Re: Bad air/fuel mixture
its running super rich... i dont know if you have acsess to a scan tool , if you do verrify that the maf and tps are working. tps 0.5v closed throttle and 5.0v wide open and maf 3-4g/s roughly (idle) then increases with more air. check the fuel trim too. if the long term is reading -10% or more its trying to slow down the fuel, explains the sooty rich mixture. maf sensor is likely , but things like an engine coolant temp sensor (ect) , bad fuel regulator (fpr) or a clogged air filter can cause this too.
10-12-2011, 02:36 PM
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Re: Bad air/fuel mixture
You really need to scan the vehicle to check the codes. After that I'd start by looking at the 02 sensors and vacuum system. Leave the MAF unplugged to eliminate it as an issue - the ECU will use default maps that allow the car to still run fine if the other sensors are working properly.
10-12-2011, 02:57 PM
#7
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Re: Bad air/fuel mixture
I was fuddling with it today, no progress
I do have a scanner at the shop and I checked everything and things look to be running as they should and then something triggers to the to stall out...
so I talked to another mechanic today. He is a VW specialist in the plaza next to mine.
I got it going in there tomorrow for an hour or two....
right now I've narrowed the problem down to either Witchcraft or Voodoo...
Ive looked at this damn car too long, you really need to feel they way the car is running to be confused by it.
I do have a scanner at the shop and I checked everything and things look to be running as they should and then something triggers to the to stall out...
so I talked to another mechanic today. He is a VW specialist in the plaza next to mine.
I got it going in there tomorrow for an hour or two....
right now I've narrowed the problem down to either Witchcraft or Voodoo...
Ive looked at this damn car too long, you really need to feel they way the car is running to be confused by it.
10-13-2011, 12:02 AM
#8
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Re: Bad air/fuel mixture
A word of caution: be sure that all this rich running is not diluting the fuel too much - you can damage the bearings/cam journals due to low lubricity.
By any chance is the car running fine until it warms up a bit (not fully), then it starts running improperly? If so, it's almost surely one of your sensors (02 in particular).
10-13-2011, 07:19 PM
#9
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Re: Bad air/fuel mixture
my BMWs never gave me any unknown problems, the floors just rotted out of them.
it doesn't run fine, just better.... anyways the car has was at a trusted mechanic today... he couldnt find the problem, told me to talk to call another guy who has better equipment, long story short, it's back at Volkswagen again.
I'm just lucky that nobody has charged me yet.
it doesn't run fine, just better.... anyways the car has was at a trusted mechanic today... he couldnt find the problem, told me to talk to call another guy who has better equipment, long story short, it's back at Volkswagen again.
I'm just lucky that nobody has charged me yet.
