Unclejake Posted November 29, 2011 Share Posted November 29, 2011 2002 Audi fuel injected 3.0 V6 auto. 180,000kms. The idle is steady when the engine is cold but once up to operating temperature it fluctuates between 700 and 1,100rpm. This problem has existed for several months. The throttle body and all filters have been cleaned. The sparkplugs are fresh. The engine and transmission are otherwise running perfectly. There are no fault codes showing. Audi says it needs a new throttle body and module @ $2,300. I am going to get the thing into my own shed tonight to look for a vacuum leak, but I am not quite certain if a PCV valve could give me trouble only when the engine is hot ............ or could there be an idle stepper motor that is masking the problem when the engine is cold? Injection. It sucks. Any other advice before I start pulling things to bits? Quote Link to comment Share on other sites More sharing options...
Alfashark Posted November 29, 2011 Share Posted November 29, 2011 Got access to a VAGCOM scanner? I know if the battery is disconnected and/or the TB is disconnected and removed it needs to be realigned via VAGCOM - only do-able with the real deal, not the generic scanners. As for the stepper motor, I'm not sure what year the V6 is in this article, but he's got a how-to as far as removal and cleaning... http://wiki.audiworld.com/index.php?title=Idle_Control_Valve&oldid=1623 Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 29, 2011 Author Share Posted November 29, 2011 I don't have a scanner but the vehicle has been to two different Audi dealerships with no result (except for the quote in my fist post). It is also of note that this engine does indeed seem to be a 'drive by wire' motor (as you are suggesting). Blimey. Anyway, I had a better play with it tonight and there are two notable additions to the symptom (all tests done at operating temperature): 1) In the workshop I can replicate the 'surging idle' problem at any RPM below 1,500 or so. The engine speed will rhythmically surge by 200rpm with a steady foot on the throttle (in park). 2) The symptom is worse if the oil cap is removed. I took the oil cap off in an attempt to test the PCV. I am not certain what my results indicate. Quote Link to comment Share on other sites More sharing options...
KKtrips Posted November 29, 2011 Share Posted November 29, 2011 A lot of engines have to be fully sealed to run properly - if you pull the dipstick out even half an inch it introduces an airleak into the engine and can cause high idle. This is what is happening when you remove the oil cap. It isn't necessarily what the problem is - you are just able to replicate it through other means. However make sure there are no dipsticks half out, no breathers disconnected etc etc. TBH it sounds like the idle stepper motor is sticking open a little from excessive carbon around the seat - it seems to be a very common problem with Euro vehicles - Peugeots are renowned for it.. Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 29, 2011 Author Share Posted November 29, 2011 OK. Ta. I will try to take a look at that next (after a check of the service history to see if Audi tried that already), but if a stepper motor was present (I dunno with these drive by wire things) would we still see the problem at 1,500rpm?. Quote Link to comment Share on other sites More sharing options...
KKtrips Posted November 29, 2011 Share Posted November 29, 2011 I doubt you would see it at 1500rpm if there was a load because the volume of air being consumed is heaps compared to the small amount that would be leaking by the stepper motor. However free revving in neutral it would show up more readily because the air leaking past the stepper valve seat would be the same but the amount of air being consumed is much much less. So comparatively it would make an impact.. PS - this is all theory - I am electronically retarded and would have sent it to be tested on the VAG computer ages ago.. LOL Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 29, 2011 Author Share Posted November 29, 2011 Ta. I'll be fucked if I know what is wrong with it.... but it isn't a major and it still drives just fine. I am unkeen to spend big coin to fix it though.... but there are a few being wrecked around the place and one guy (TradeMe private sale) wants $130 for the throttle body assembly (better than $2k). I just don't know if his one will fits or not, or even if the throttle body could be the problem. I will take a look at the stepper option. Quote Link to comment Share on other sites More sharing options...
Testament Posted November 29, 2011 Share Posted November 29, 2011 yeah +1 to checking any kind of stepper idle bypass thing and blasting the crap out of it with carb cleaner/air/what have you, I know a number of fiat/lanica motors do that when they get gunked up, but usually its the other way around, more pronounced when cold. but basically this sort of thing is why audis are the work of the devil. Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 29, 2011 Author Share Posted November 29, 2011 They drive like an angel though. Ha! Quote Link to comment Share on other sites More sharing options...
Spencer Posted November 29, 2011 Share Posted November 29, 2011 YEa it would be interesting to see what controls the idle on this thing, late model Audi stuff is abit above my league but some form of idle stepper motor would be the first place to look. Quote Link to comment Share on other sites More sharing options...
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