Idling problems ��

liamsmith672 · 05-01-14, 06:42 PM

Hey guys... right...... Audi 80 B3 2.0 16v Quattro 4cyl

For quite a while had an idling issue , the car on cold start up revs to just bellow 2000rpm on its own till gets some level of heat into her then settle to just over 1000rpm OR will idle just enough to stay running but 70% will cut out because of such low revs. this pattern happens all the time on long or short journeys.

I have tried an idle control valve that was given to me as a spare (don't no whether any good) but the car behaves the same with my own or spare one fitted, not sure as there no difference in running with either that its the idle valve?
Also tried a new lamda sensor.

im going towards the idea off fuel starvation from somewhere, or timing but problem happened very randomly after a service?

ANYONE with ideas of anything please help !!!! greatly appreciated!!!

msh · 05-01-14, 06:52 PM

Fuel starvation? Please...

ISV is VERY unlikely cause, but let's begin with it. Are both ISV's Bosch, made from alloy? You can test them by applying power from battery using two wires - moving part should move quickly and sharply. If they does, and adjustment bolts haven't been touched - or, at least, you can see that without power there's only small gap and moving further it closes first, we can presume they are fine.

While 2.0 R4 engines have basically the same KE-jetronic like NG/NF/AAR, it has some interesting quirks because of adaptations. Root of your problem most likely is worn out MAF potentiometer, but first you must check throttle etc. Throttle should be fully closed, with idle switch activated, and if there is any idle adjustment screw on throttle body, it should be fully in, and adjusting it shouldn't make any difference in idle speed.

Do you have multimeter and you know how to use it?

liamsmith672 · 05-01-14, 07:07 PM

yeahh I didn't think it was, before hand seemed like then but then thought naaaaa!!!! the outer casing of both are just plastic one has a faded audi sticker on? (spare) other is just black plastic! I shall test them both tomorrow and yep im a technician multimetre is all good! ha.

ok where might the MAF sensor be on the 6A engine? the idle screw is all way in never touched it

msh · 05-01-14, 08:00 PM

First get yourself proper ISV. I experienced something similar on one 3A [which engine management-wise is basically identical to 6A] - it also had plastic ISV - while my 3A had correct ISV and while it had worn out MAF potentiometer, it has noticeably lower cold idle speed, while also too high. Should be alloy one, code 034 133 455 B, it was used on 3A/6A/AAD/ACE/NF/NG/AAR, also 12v VR6 engines and 20vt engines.

In order to test MAF potentimeter, you should make sure that idle switch is working and mixture and ignition timing is correct. I won't comment on timing, as for mixture, easiest way to tell that is by connecting multimeter in series with control pressure regulator in current measurement mode, either by removing one pin in connector, if you know what you're doing or using another similar connector, connecting it to harness connector by sticking wires in it - before engine start, with multimeter on - must be ~ +120 mA before start and between -10 mA and +10 mA and fluctuating at around 5mA at idle - with engine warm, of course.

If that's fine, you can test MAF potentiometer. It is located on the outer side of injection unit, that three pin connector. Pins at both ends are power, one is ground, another is +5v, one in the middle is signal. Must be around 0,67v @ 850 rpm - in order to achieve those 850 rpms, use pliers to squeeze ISV hose.

liamsmith672 · 05-01-14, 10:39 PM

Brilliant I shall try and test this all tomorrow mate, my fingers are crossed I can get to a conclusion and cause.
Its all very annoying!!

liamsmith672 · 06-01-14, 10:24 AM

If it turn put to be the MAF any idea where to get a new one from??

msh · 06-01-14, 07:00 PM

1) used part. Especially knowing that very often these 20-25 years old cars have quite low mileages in UK.
2) there's some new stuff in ebay - both for audi and also some mercedes stuff that can be adapted.

liamsmith672 · 07-01-14, 11:19 AM

Ok mate, i have found unplugging the MAF sensor and driving it its pretty much 1000rpm idle speed?

BIGGYIN · 07-01-14, 11:39 AM

Temperature sensor?

liamsmith672 · 07-01-14, 12:26 PM

Would that cause all of this in a B3 6A engine?

07-01-14, 11:39 AM	#9
BIGGYIN 4 ring whore! Classic Audi Club Member Join Date: Mar 2009 Location: Merseyside Posts: 7,976	Temperature sensor? __________________ q90 B2 Type 85 - q90 B2 Type 85-PROJECT-ABY 20vt KARL. Injection is nice but I'd rather be blown

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05-01-14, 06:52 PM	#2
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	Fuel starvation? Please... ISV is VERY unlikely cause, but let's begin with it. Are both ISV's Bosch, made from alloy? You can test them by applying power from battery using two wires - moving part should move quickly and sharply. If they does, and adjustment bolts haven't been touched - or, at least, you can see that without power there's only small gap and moving further it closes first, we can presume they are fine. While 2.0 R4 engines have basically the same KE-jetronic like NG/NF/AAR, it has some interesting quirks because of adaptations. Root of your problem most likely is worn out MAF potentiometer, but first you must check throttle etc. Throttle should be fully closed, with idle switch activated, and if there is any idle adjustment screw on throttle body, it should be fully in, and adjusting it shouldn't make any difference in idle speed. Do you have multimeter and you know how to use it?

05-01-14, 07:07 PM	#3
liamsmith672 Grown up member Join Date: May 2013 Location: Kent Posts: 115	yeahh I didn't think it was, before hand seemed like then but then thought naaaaa!!!! the outer casing of both are just plastic one has a faded audi sticker on? (spare) other is just black plastic! I shall test them both tomorrow and yep im a technician multimetre is all good! ha. ok where might the MAF sensor be on the 6A engine? the idle screw is all way in never touched it

05-01-14, 08:00 PM	#4
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	First get yourself proper ISV. I experienced something similar on one 3A [which engine management-wise is basically identical to 6A] - it also had plastic ISV - while my 3A had correct ISV and while it had worn out MAF potentiometer, it has noticeably lower cold idle speed, while also too high. Should be alloy one, code 034 133 455 B, it was used on 3A/6A/AAD/ACE/NF/NG/AAR, also 12v VR6 engines and 20vt engines. In order to test MAF potentimeter, you should make sure that idle switch is working and mixture and ignition timing is correct. I won't comment on timing, as for mixture, easiest way to tell that is by connecting multimeter in series with control pressure regulator in current measurement mode, either by removing one pin in connector, if you know what you're doing or using another similar connector, connecting it to harness connector by sticking wires in it - before engine start, with multimeter on - must be ~ +120 mA before start and between -10 mA and +10 mA and fluctuating at around 5mA at idle - with engine warm, of course. If that's fine, you can test MAF potentiometer. It is located on the outer side of injection unit, that three pin connector. Pins at both ends are power, one is ground, another is +5v, one in the middle is signal. Must be around 0,67v @ 850 rpm - in order to achieve those 850 rpms, use pliers to squeeze ISV hose.

05-01-14, 10:39 PM	#5
liamsmith672 Grown up member Join Date: May 2013 Location: Kent Posts: 115	Brilliant I shall try and test this all tomorrow mate, my fingers are crossed I can get to a conclusion and cause. Its all very annoying!!

06-01-14, 10:24 AM	#6
liamsmith672 Grown up member Join Date: May 2013 Location: Kent Posts: 115	If it turn put to be the MAF any idea where to get a new one from??

06-01-14, 07:00 PM	#7
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	1) used part. Especially knowing that very often these 20-25 years old cars have quite low mileages in UK. 2) there's some new stuff in ebay - both for audi and also some mercedes stuff that can be adapted.

07-01-14, 11:19 AM	#8
liamsmith672 Grown up member Join Date: May 2013 Location: Kent Posts: 115	Ok mate, i have found unplugging the MAF sensor and driving it its pretty much 1000rpm idle speed?

07-01-14, 12:26 PM	#10
liamsmith672 Grown up member Join Date: May 2013 Location: Kent Posts: 115	Would that cause all of this in a B3 6A engine?