Audi 100 low idle

[niall4313]

Hi hope someone can help me with this, I recently purchased a 1995 audi 100. Its the 2.0e abk engine model. Problem is when I start it even though it starts easily the revs are very low between 800 to 1000 and I have to rev it to keep it from dying. Once it gets going it drives fine although at idle it does seem to be misfiring a little. The guy I bought it off replaced the maf but this doesnt seem to have fixed the problem. Any one have any suggestions as to what it may be? Thanking you in advance..

[kenney]

The fault suggests a faulty temp sensor,have you had a fault code read?

[niall4313]

No havent had a diagnostic on it yet was hoping it might be a relatively simple fix, would the temp sensor still affect the idle even when the car was warmed up?

[kenney]

Yes

[niall4313]

Ok thanks Ill try that first hope its that simple, will post an update .

[diane]

re idle problems on the old 100. I have a 100e 2.3 audi 1992 in amazing condition with 118k on the clock. have all the service history so i know that it has been looked after. As i have done all my own servicing and repairs on it i know its in fine fetle. Anyway a couple of weeks ago the idle starting playing up rising up and down then surging until it stalls. After reading all the forums on the problem i cleaned out icv with carb cleaner and brake cleaner put it back on started it up and it idled as it should that is until it warmed up then it started playing up again. Okay took the icv of again very easy on this engine by the way right in front on the left top of the head as you look in. Cleaned it again it was clean anyway and the cylinder inside free when twisted clicking back to its stop. Anyway same result. I checked and cleaned all the the sensor connecters and looked for any vacume pipes for leaks with engine running with no joy. My next plan is to change the temp sensor as i understand this sends imformation to the ecu which controls the idle speed,fuel control and ignition timing so i am thinking what the heck give it a try. I will get back to let you know what the results if any.If anyone has any other information i would be grateful. I know its an old chestnut but i want my baby running smooth again.

[kenney]

You can check the resistance of the sensor approx. 20 °C approx. 2.5 kω approx. 80 °C
approx. 330 ω

[diane]

Thanks Kenny for your interest in my problem but you have just gone over my head. I have an analoge meter which i use mainly for checking resistance and continuity, i had a look at my meter and see horseshoe shaped thing with rx1k and rx10 next to it is this the setting i use for testing . Sorry about my ignorance Thanks again.

[kenney]

That is correct

[diane]

Update on my idling problem. As Kenney suggested i tried the meter test on the temp sensor. I warmed the engine up to approx 20c and found the reading on the bottom of the scale.Ithen let the engine warm up until just under 90c at that point the needle was bouncing all over the place. I thought well it must have gone bad. Just then a friend of mine called in to see me and suggested i tap the icv lightly when the engine is ticking over.Nothing to loose i tried it with a handle of a screwdriver, The idle rocked up and down a couple of times and settled for about 10 seconds then went rough again.I am really confused now. The strange part is if itake it out on the road it drives really well until you have to stop in traffic then you can fee the rough idle. Anyway i rung around a couple of local motor factors to see if they had any sensors or could get one but i had no joy, So i bit the bullet and rung an Audi dealer and the man said 42quid + vat. I thanked him for his time and hung up. Well thats the saga so far any one Know where i can get one of these .The engine is the 5 cylinder AAR year 1992 2309cc. Thanks for your patience.

[kenney]

It might be an idea to have a fault code read

[diane]

Thanks again Kenny ihave a Haynes manual but do not know where the connector is to hook up the tester. Anyway i will try and find a sensor. As i said the car is driving ok its just annoying. Iwill ask around to find some one who can test the system. Thanks again.

[diane]

Update ihave been able to find a sensor but cant pick it up until monday. 20 quid bosch make . Ill keep you posted.

[diane]

Re poor idle. Fitted new temp sensor today alas no joy. Next step is as Kenny said is to get the system checked out. Now looking around my area for anyone with vag-com. I found the connectors in the fuse box drivers side with the bonnet up. I believe they are called 2+2. Anyway see you next time.

[niall4313]

same as, changed the sensor today made no difference

[diane]

Re poor idle. Have found someone with vag-com locally but cannot do it until tuesday. I spent about 2 hours yesterday every vac pipes and hoses attached to the engine was taken off and cleaned. To be honest they where all pretty clean just alittle bit of muck in the big one coming out of the engine block. All of them were in good order with no splits or damaged. I also took of the big flex pipe from the top of the air filter housing onto the inlet manifold. inside you can see two butterflies one smaller then the other.There was a fair bit of muck on these and i thought ahah. After blasting away with carb cleaner and cleaning very gingerly with nice clean old t shirt i then give a good blast with brake cleaner.I know i should have taken that unit off but have not got new gasket. Anyway i also noticed that when i twist the throttle back and fore i could hear the throttle switch clicking so assume that it is working. By the way the air filter is new. After putting every thing back to together it eventually started and settled at around 1000 rpm took it out on the road to warm it up. it is idling much better when warm but let it run in the drive for 10 minutes. Idle is about 600 rpm and it will jump up to 1200 and then drop to nearly zero then settle at 600 again.The annoying bit is it drives really well its just the idle bit.Ill update after the vag-com man does is thing.PS I am leaning more and more toward the icv.:confused:

[diane]

Update. The vag-com man did not have the right connectors so could not do anything for me. I have been checking out around the net and found that this seems to be a very common problem with vw audi cars. I found one site where they talked about an idle switch which if not working would mess up the idle. So out with my trusty meter and started checking the idle switch connector for any life. It is a three pin job on top and to the rear of the throttle body. I could not get any reading on any combination of the pins. As i was looking at the cable(its about six inches long) i saw there was a kink in it. As i fiddled around with it the meter needle started jumping around.Its such a tight sqeeze in there i decided to bite the bullet and take the throttle body off. Four 6 mil hex bolts and a few vac pipes later it was on the bench.Had alook at the cable and found one of the wires broken so cleaned and soldered it back and nice length of insulation tape. I found that if i touched pins 1 and 2 with the probes on the meter the needle would go about half way up the guage and if i twisted the throttle the needle would drop to zero. I could hear the idle switch clicking when i did this.I put the throttle body back on with gasket sealer on gasket hooked every thing back up had a cup of tea and fired her up.Revs about 1000 let it idle five minutes thencame down to around 700 which is about what it always did before this problem began. I took it out on the road onto the bypass and through the town with plenty of stops and starts and my baby did not miss a beat. Idle was about 800 and steady which is great.I know my methods are basic and believe i have been pretty lucky but hope that my posts have been enlightning to someone.PS i would like to thank Kenny for his interest.

[niall4313]

Also managed to solve my problem today. The guy i bought the car off told me he had replaced the air flow meter already but it hadnt cured the problem, but since i had a spare one off another car in the garage i decided to replace it again anyway. So straight away there was a noticeable difference in the idle of the car, it was still not perfect however and after a bit more thinking i decided to unplug the lambda sensor the from the connection on the bulkhead this made all the difference now the car is running spot on so all i need to do now is replace the lambda. i have a spare new one anyway on the shelf so ill do that tomorrow