Lumpy idle from cold start clears after 30 seconds or so?

[Adam Smee]

Hi all,

I have had my A4 B6 TDI 130 quattro sport avant for a couple of months now and been really happy with it. It pulls well, feels rock solid and looks great Its a nice change from my previous vauxhalls and fords . Anyways, I have a slight problem when the car when I first start it. The intial turn of the key fires it up straight away but after a couple of seconds feels like a slight misfire on one or two pots coupled with a grey sooty look from the exhaust, after half a minute it clears up. Its done 135 k. Had a full service history and just changed the cambelt, filters and oil. When I drive off there isnt any misfire or hesitation. Could it be a fuel pump issue? I have enquired into replacing the injectors and have been met with a scary price tag! The car hasnt been mapped and trying to flush it through with a heavy redex mix. Please help!

Thanks all

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[alyrian]

Could be a faulty injector harness as it sits within the top section in oil... Just diagnosed this on mine, waiting for the new part now (cost around 50 pounds for A3).

One way to check is to remove the connector to the rocker cover, there's 5 pins (3 on left, 2 on the right), bottom left is the ground and check the resistance. I have 0.8 ohm on the good cylinders, 0.3 ohm on cyl 2 (misfire when cold too for 1min, when hot it goes up to 0.5 ohm). I found that on another forum, can give the links later.

 

[nokia_aid]

Could be a faulty injector harness as it sits within the top section in oil... Just diagnosed this on mine, waiting for the new part now (cost around 50 pounds for A3).

One way to check is to remove the connector to the rocker cover, there's 5 pins (3 on left, 2 on the right), bottom left is the ground and check the resistance. I have 0.8 ohm on the good cylinders, 0.3 ohm on cyl 2 (misfire when cold too for 1min, when hot it goes up to 0.5 ohm). I found that on another forum, can give the links later.

hmmm that could be whats wrong with mine,im guessing i unplug it check the resistance when cold then plug it back in and start the car then test again when its all warm.is that right?????

 

[alyrian]

Hi nokia_aid,

I had a look on the one I removed, in fact what I said earlier was wrong, on the plug there's 3 pins on the left and 2 on the right.
3 pins are from top to bottom: Cyl 1, Common, Cyl 4
2 pins are from top to bottom: Cyl 2, Cyl 3
So in fact my measurements earlier were wrong. But VCDS was telling I had Cyl 2 misfiring.

I've changed it and now the car runs great, it costed me 52 pounds for the part.

Try measure both cold and warm if there's any difference

 

[Mackers]

..... faulty glow glug??