high idle speed s4

[Tuffty]

my s4 has randomly started idling at 1100 - 1200 rpm
i've checked all the hoses i can get to for leaks, the recerc valves are seating nicely,
i've cleaned the throttle flap and reset it.
the only fault codes i'm getting are the EGT sensors (supprise supprise lol ) and an intermitant lambda heating fault.
the car idles smoothly drives ok, although you can feel a slight surging at very light throttle.

any thoughts?

 

[SonicDeathmonkey]

Mine did exactly the same until I had the EGTs sorted, except it would also hessitate at about 3,000 rpm before kicing off again. Weird.

 

[SonicDeathmonkey]

bye the way, how does the 84 GTE turbo go? I used to have a J plate GSi Red Top. When I went to pick up my brand new Fiat Coupe turbo in '99, the woman at the fiat dealer asked me if "I made it myself". I didn't know what to say to her...

 

[Tuffty]

mine does sometimes hesitate which i put down to the EGT's but it's idled fine up until now which is what i find odd.

The astra's just shy of 290bhp, so makes the S4 seem very tame lol

 

[ScottyP45]

cts?

 

[Tuffty]

cts?

Think that'll be my next port of call, started it today from cold and the idle dropped down to normal after a min or so, but after driving it was back up to 1200.

 

[SonicDeathmonkey]

Doh, I should have said that I changes the CTS at the same time!!!

 

[mwarrey]

What's CTS? I have the same issue on mine

 

[aragorn]

Coolant Temp Sensor.

Easy to check with vagcom before condemning it though.

Does your coolant guage behave? it should quickly climb to 90 in about 5-10mins and stay there resolutely.

 

[Tuffty]

changed the cts, no joy, looks like i'm gunner have to put my hands in my pockets for some new egt sensors and hope that solves it.

 

[ScottyP45]

a log of vag com for various values might provide a picture mate before you spend any more cash, a cheap lead and a run using the laptop then post the graphs, fuelling, boost, maf, temps, etc etc its all in there

 

[Tuffty]

have the free version of vag com but my laptop battery died a long time ago so it needs permanent 240v lol, what should the maf read under load on an s4?

 

[ScottyP45]

240v inverter plugged into the fag lighter - thats what im using, laptop wont run more than a minute off the mains lol

 

[Tuffty]

chucked a couple of Exhaust temp sensors on and she's still idling high. tried with the maf unpluged and she coughs and splutters but idles lower.
bring back carbs! lol

 

[ScottyP45]

tps calibration maybe work?

Asda selling a 80W inverter that plugs into the fag lighter, £15 and it'll run yer laptop in the car for ever...

 

[Tuffty]

have tried reseting the tps. will run off some logs tomorrow, at least the fault codes are clear now lol

 

[Tuffty]

think i've found the problem, looking at the logs the bank 2 lambda is basicly shagged and not doing anything.
Why do I get the feeling that bank 2 is the passenger side one which a complete sod to get to lol.

 

[ScottyP45]

haha yeah it probably is mate

Good find. Likely its preventing closed loop mode operation eh.

 

[Tuffty]

lambda now fixed, still not idling right.
think it's gunner catch fire soon !

 

[Tuffty]

Have now sorted it.
turned out that the throttle flap had come out of alignment, and the foot on the throttle with the ignition on then off doesn't work on the S4, a quick reset on vag-com and job jobbed.

Ross-Tech: VAG-COM: Throttle Body Alignment

 

[S4twiggy]

if you leave the ignition on for about 30 seconds ive been told the TB resets itself

 

[Tuffty]

if you leave the ignition on for about 30 seconds ive been told the TB resets itself

Doing that only sets the max open and shut of the flap. Not the idle / overun etc positions

 

[aragorn]

TBH i cant believe that.

Seems completely stupid to design an ECU that every time the battery was removed the car NEEDS to be plugged into a dealer computer to reset the throttle body. Given the throttle position is a safety critical component, there MUST be an automatic alignment system built in.

Did you actually try just turning the ignition on without touching any of the pedals and leaving the car for a minute or two to do its thing?

 

[Tuffty]

Trust me I've spent 3 weeks searching for an answer to this. I've tried with and without moving the throttle and various lengths of time with the ign on and off. Ive even left the battery off overnight to try and get it to reset. But the vag-com way was they only thing that worked.

 

[aragorn]

Fair enough. Maybe yours was extra-stuck or something

 

[Swifmcvay99]

Hey Guys,

Mine is doing exactly the same thing, I will try the turning off the ignition and leaving it for a minute and see what it does, I don't know anyone in the surrey area with a VAGCOM which is rather annoying, because when I'm sat at the lights,the idle is so high, people think i want to race them, the only way i get it to go down a little to about 1k rpm is to turn the aircon on

 

[Swifmcvay99]

Just an update to this, the turning on the ignition and leaving for a few minutes doesn't work i'm afraid.

Looks like a vagcom fix

 

[slepy]

I disconnect the battery in mine every night because something drains it. Runs fine after couple of mins with ignition on.