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N52 unsteady idle worse on cold(ish) start.

J

Jl-c

Active member
Shropshire
Firstly, if this has been covered I apologise. I have searched and been unable to find a definative answer, assuming there is one! When I start my 3.0si when the car is not hot the idle hunts up and down at 100 to 200 rpm around 'normal' idle ie. 850/900 hot and 1000 or so cold. Is this a) normal or b) something to do with the VANOS? I am only doing relatively short journeys at present but am averaging 19mpg but am driving a little spiritedly shall we say. A few months ago took it to Devon and returned 38mpg which I was very impressed with, but now have no comparison to work with unless I waste a load of fuel going to Devon again for no reason. :rofl:
I guess I am looking for "oh they all do that" but I suspect they don't, or clean/replace the solenoids :? Thanks in advance. Jonathan
 
Mines has had an occasional wee blip at idle since I bought it 3 years ago. I don't do many miles, approx 8000 in 3 years, so I don't worry about it. Would be interested in finding out if it can be sorted or not.

Or it could just be that wood trim as I don't think mine has been as bad since I removed it :D
 
bazza190 said:
Mines has had an occasional wee blip at idle since I bought it 3 years ago. I don't do many miles, approx 8000 in 3 years, so I don't worry about it. Would be interested in finding out if it can be sorted or not.

Or it could just be that wood trim as I don't think mine has been as bad since I removed it :D
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No no, you've got it wrong. Wood trim and a stubby aerial makes a Z4 perfect. I think someone with aluminium or piano black trim has put a curse on it. :poke: :rofl: :o
 
A stubby......are you for real!!! Whippy all the way, doubles the value of you car and at least 10 mph faster through the Twisties :poke:
 
Regarding the erratic idle when cold, it should be rock steady. Could be a number of things, have you got any error codes? I would check your injectors, one could be leaking. Overnight it will weep fuel and will give an erratic idle until hot and the fouled plug cleans up. Do you have an inlet manifold leak? O2 sensor functioning correctly? Coils ok? Plugs and plug leads ok? Need a code reader. I bought a carista but for my Audi A3 and golf Mk7 but it also reads code for the zed. It was only £16 on Amazon with 1 months free pro software and a yearly fee of £33. If you don't have Carly see if there is someone on the forum who is willing to check your zed codes. Good luck!
 
All appears physically OK at least leaks etc. all seems to be good. Obviously I can't check coils or injectors.
No codes at all except telling me the cd changer is knackered and I knew that!
 
Jl-c said:
All appears physically OK at least leaks etc. all seems to be good. Obviously I can't check coils or injectors.
No codes at all except telling me the cd changer is knackered and I knew that!
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Hi, try unplugging the eccentric shaft sensor and see if the erratic idle goes away.
Rob
 
Ok, thanks. Will try that tomorrow when hopefully the monsoon season will be over! That part if memory serves is stupid money isn't it? No doubt that will be it :(
 
Jl-c said:
Ok, thanks. Will try that tomorrow when hopefully the monsoon season will be over! That part if memory serves is stupid money isn't it? No doubt that will be it :(
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Yes it’s expensive, i think it can be bought cheaper from Germany :?
Rob
 
Mine has done this from the day I got it, asked the same question a while ago and seems to be quite common. Its certainly never caused me any issues in 3 years and 30000 miles :) :thumbsup:
 
Now you see that was the answer I wanted, 'They're all like that' :) , Oh well, I wish. I am still going to have to find it now I've started, eccentric shaft sensor tomorrow. :headbang:
 
Just been thinking back to when I had a Mk2 golf gti many moons ago, I had a similar problem, turned out to be a problem with the fuel pump and low pressure, the engine wasn't getting the correct fuel/air mixture causing an erratic idle, but this was also when hot. VW main dealer couldn't solve it, took it to a VW indy and they had it running perfectly within 20 mins, after they fitted a new fuel pump. Is the Maf functioning correctly? Does it have electrical continuity at all times? Pull it and make sure the contact pins are ok and not corroded/tarnished/dirty, while it is idling erratically you could try wiggling the body of the maf about/pushing it in to ensure electrical contact.

Just noticed you are a shropshire lad, you could telephone http://www.autotechperformance.co.uk/ speak to Peter Thorpe and pick his brains, I bet he has experienced this! If it needs to go in for repairs he is very good, not the cheapest of indys but the best for many miles if not the UK, he has a fantastic reputation. Please note I have nothing at all to do with this indy so not touting for business!

You could just wait until a CEL is thrown, bound to get worse and see what the code is.
 
Thank you. I know Pete well, known him for probably 15/20 years! Since he worked for Nigel Moseley (also local) who is the E30 M3 guru. Interesting point about fuel pressure though, will check what it is.
 
Hello,

Mine had a similar issue to this in the past (the erratic idle caused mine to cut out a number of times too). In my case there were no codes. I cleaned the solenoids which seemed to help for a while but the issue came back so I replaced both vanos solenoids and that fixed the issue. Mines a 2.5 n52. Good luck getting it sorted.

Cheers,

Jon.
 
I think you got it right yourself in first post. 1st step is to clean / replace the vanos solenoids. 2nd is to inspect the eccentric shaft sensor for signs of oil leakage, 3rd is to tap the valvetronic motor when it's doing the erratic idle thing and see if it changes it. I wouldn't say it's normal behaviour though.
 
R60BBA said:
What’s the mileage?
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89K

JonBooth said:
Hello,

Mine had a similar issue to this in the past (the erratic idle caused mine to cut out a number of times too). In my case there were no codes. I cleaned the solenoids which seemed to help for a while but the issue came back so I replaced both vanos solenoids and that fixed the issue. Mines a 2.5 n52. Good luck getting it sorted.

Cheers,

Jon.
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thanks Jon.
 
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