9A Idling Issues - still a problem, getting annoyed now!

[borarob 0]

Hey all, I have searched and read lots on idle issues, but nothing seems to be quite the same as my 'problem'

 

When I start the car from cold the car will idle at or just above 1000 for a while and then will slowly drop to about 900 as it warms. In my book, expected behaviour. While still getting to full temperature it idle at 900 pretty smoothly when pulling up etc, but very occasionally it will stay at 1200 and sometimes will rise up to 1700, a blip on the throttle will bring it back down to 900.

 

Now when the car is properly warm, the above problem seems to go away but the car will idle at or just above 1000 instead of 900. I have cleaned and install another ISV and have the original one soaking in some carb cleaner (original was a black plastic coated item, new one was polished metal, both have VAG markings).

 

Does this sound like the ISV still and I just haven't cleaned it well enough or something else. The previous corrado I had had a dodgy accel cable which caused idle to stick at about 1200 (pulling the accel pedal up with my toes used to solve that), so have ordered a new cable just to rule that out. Would cleaning the throttle body and butterflies also be worth doing in an attempt to cure this?

 

thanks guys, even though the corrado is showing its 'character' with these little niggles I am so happy to be back driving one! Amazing machines!

Edited September 20, 2013 by borarob

[bmwcompact 10]

It does sound like an ISV related problem. But if the contacts/wiring are dodgy then cleaning/changing the ISV wont cure the problem. However theres a more likely cause. On the end of the throttle spindle (on the underside) is a potentiometer. Its not a throttle position sensor, but in effect its a couple of switches, which tell the ecu when the throttle is closed and when wide open. When the ecu thinks the throttle is closed (tick over) it then operates the ISV. Its not uncommon for this potentiometer to sometimes operate correctly and sometimes not so and hence to cause problems on tickover. There are many threads on this but, in short, my own experience is that since its an intermittent issue, the pot may check out OK with a meter but still be the problem. Since a new pot is silly money, a used one ( you usually have to buy the throttle body complete) is the answer. I think the KR engine (Golf and Corrado) had 2 micro switches on the throttle body rather than this pot so I think its specific to the 9A engine.

 

I find Google to be a better search engine for Corrado issues (which includes posts on this forum) than the search function here on the forum!!

 

---------- Post added at 6:23 PM ---------- Previous post was at 6:22 PM ----------

Edited July 8, 2013 by bmwcompact

[borarob 0]

I only getting increased idle when the engine has warmed up now 1000rpm rather than 900. Any temp sensors this could be? It's running a little rich too...

[davidwort 0]

sounds like it could be lambda related as the ecu doesn't use the lambda feedback until the engine is warm.

[borarob 0]

sounds like it could be lambda related as the ecu doesn't use the lambda feedback until the engine is warm.

 

been reading various posts which talk about the blue temp sensor, is this relevant to this issue / the 9a engine! (excuse any ignorance here i'm no mechanic!)

[davidwort 0]

I seem to remember that if you pull the plugs from one or more of the temp sensors, that the ecu will ignore inputs and run using stored fixed 'average' values to keep it running. But I've also come across a fair few 9A's that have failed or cheap generic pattern lambdas that cause loads of idling problems, it's easy enough to check temp sensors by simply measuring their resistance as the engine warms/cools to make sure they are giving a value in range and with no odd spikes etc, for the lambda an MOT test station/garage should be able to check out what's going on.

[borarob 0]

I seem to remember that if you pull the plugs from one or more of the temp sensors, that the ecu will ignore inputs and run using stored fixed 'average' values to keep it running. But I've also come across a fair few 9A's that have failed or cheap generic pattern lambdas that cause loads of idling problems, it's easy enough to check temp sensors by simply measuring their resistance as the engine warms/cools to make sure they are giving a value in range and with no odd spikes etc, for the lambda an MOT test station/garage should be able to check out what's going on.

 

 

Well I unplugged this and idle problem still there. What is it and what should have changed due to being unplugged and if nothing changed does it mean whatever it is is broken?

[davidwort 0]

That's just the cold start injector, won't make any difference in running

[borarob 0]

Ok that makes sense, cheers :)

[bmwcompact 10]

"been reading various posts which talk about the blue temp sensor, is this relevant to this issue / the 9a engine!

 

No! There's confusion between the different engines. The 9A has 2 temp sensors. There's 027919501 which is on the end of the block above the gearbox and closest to the bulkhead. This has a single wire to it and is for the dashboard temp gauge only. Its widely available on Ebay and the usual suppliers.

 

The other one is also on the end of the engine block above the gearbox, nearer the radiator, 026906161 (Bosch 0280130040. It has 2 wires to it and sends temp info to the ECU which then controls the engine appropriately. This is therefore the more important one. If you can find the VAG/Bosch part it will be about £25, theres a Meyle equivalent which VW Heritage supply for half that price the last time I looked. (The KR engine has a so called thermotime sensor: The 9A does not have this)

 

(There's actually a third temp sensor on the head near the cambelt cover: this tells the rad fan to run when the ignition is off and the block is still very hot.)

 

On a different theme, your photo shows another small issue to rectify! Theres a lead with a plastic polo like fitting at the end. Ignition lead 4 (nearest distributor) should be threaded through this, with the pointed side of the polo facing toward the distributor. The end fitting on your lead should pull off in order to thread the lead through the polo (if the leads are vw this is so, others ????). There are many threads on this!! Its an inductive loop which feeds a signal back to the ECU which tells the ECU if the ignition is being advanced correctly as engine revs increase. Lots of cars are bought with this unconnected, people have leads changed and its not reinstalled.......... Is it required, will the car run better with it fitted....apparently so else why was it fitted.

[borarob 0]

I just unplugged the isv (wiring harness) with engine running and nothing happened, no change to idle speed either way. Expected or does this mean isv is not actually doing anything anyway?

[brettski 0]

I just unplugged the isv (wiring harness) with engine running and nothing happened, no change to idle speed either way. Expected or does this mean isv is not actually doing anything anyway?

 

I to have the exact same idle issue on my corrado I have change icv throttle body and metering head and still no joy the strange thing is if I turn the car off and restart it it idles perfect for aprox 5 minuets then it all of a sudden starts to rais to 1100 rpm again I have orders a temp sensor so will try that next and see how that goes hopefully that should solve it but I am not holding my breath so keep us posted If you fix the issue with a bit off luck we can get to the bottom of it

[davidwort 0]

I'm not sure exactly when the lambda feedback starts but it sounds like yours could be dodgy too if it runs ok for a few minutes after turn-off, because the ecu is probably ignoring the lambda signal initially until the engine and cat is fully warm, you both really need the lambda tested on an mot gas analyser.

[borarob 0]

well heres an update, but first yes mine did that too, if you turned it off and on again, for a few minutes the idle would be fine before going up to 1000.

 

ok so update. i did two things to my cars enginal area at the beginning of the week. First was to clean connections at the starter motor, second was to ditch the k&n panel filter and put a standard paper one in. Now, touch wood, since then my car has seemingly idled perfectly at what i'd class as a more normal 850 +/-50. i cant see that any of those two things would have affected idle!

[jonnykillpop 10]

My VR6 is a coilpack so does'nt have the cold start valve, but I've also got a 2.8 injection Capri, had loads of them, and has exactly same cold start valve and they can leak and dribble might give you higher idle and rich running rich even when not connected, you can take it off and run if plug hole should run cold start valve will operate for few seconds if cold enough then stop, if keeps going it's bust. Also had a 3.1 Stage 2 engined Cologne V6 with it wired up as a 7th injector, worked well, but Capri's don't have ECU's probs. would'nt work with an ECU car, would wreck settings.

P.S. probs got a spare Capri one in garage somewhere.

[brettski 0]

Well I think I have sorted mine turns out my dizzy timing was to far advanced I have retarded it by a couple of degrees and its now ticking over steady at 850-900 rpm

[borarob 0]

Well I think I have sorted mine turns out my dizzy timing was to far advanced I have retarded it by a couple of degrees and its now ticking over steady at 850-900 rpm

 

Sounds interesting, is there an idiots guide available for that?

[borarob 0]

Sounds interesting, is there an idiots guide available for that?

 

can anyone tell me how to do this as my idle is still causing problems, getting worse in fact. I'm pretty sure its nothing to do with the ISV or throttle body pot as I can disconnect the ISV and the idle still goes up and down

 

its really doing my head in now!