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Thread: Z20NET Rough Erratic Hesitant Idle Issues...... Help??

  1. #1
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    confused Z20NET Rough Erratic Hesitant Idle Issues...... Help??

    Hi all,

    It seem this is an ongoing saga for a lot of people....

    I've just purchased a very cheap, 2005 Facelift Signum 2.0t Z20NET engine (SAAB B207L) (Same is Vectra C Sri 2.0 Turbo), with 70k miles, nice clean car but has this idling issue.

    When it fires up (Hot or cold) it's fairly mechanically quiet, but quite jerky for the first few seconds, like a misfire, but itís not.

    It idles ok at the high speed on initial startup, then once it drops to the 750rpm idle, it's sometimes very rough, sometimes ok but only for a short time, then it's rough again. Stuttering and shaking the whole car body, it never stalls though and no fault light.

    Have access to Snap-on Verus FCR and it has no fault codes stored. All real time data, eg temp, flow o2 look normal.

    Tried;
    Washing out the mass meter, map sensor, air temp sensor with brake cleaner.
    Cleaned and lubricated throttle butterfly, resealed the gasket.

    WD40 all the electrical connectors
    New plugs.
    New fuel filter.
    New exhaust manifold to head gasket (GM).
    All exhaust gaskets and flexi are perfect.
    Cleaned all electrical connectors in engine bay on all ecu's.
    Checked for air leaks on manifold and associated pipe work.
    It has recently had 2 new ignition coils, so I tried 2 more (No notable difference)

    Changed ignition coil insulators down to the plugs (No difference)
    Using Snap-on verus I operated all actuators and ignition coils and all worked faultless.
    New auxiliary belt and tensioner pulley.

    Disconnected battery for 30 minutes and cleared codes (Even although there were none), in the hope the adaptive ecu would relearn a new drive cycle...... no change

    I'm now thinking chains/guides/tensioner, when I first got the car 2 weeks ago, I'd say there was a definite bit of chain noise, since then I've changed to oil to 5w30 GM own oil, and it's definitely quieter.

    Going to take the cam cover, and front engine/lower chain cover off tomorrow for a look at these chains and stuff.


    Trying to get hold of a pair of cam locks to check timing. Anyone managed without?

    Also head of DMF's (Dual Mass Flywheel) causing this issue too though?

    At my whitís end, any advice gratefully appreciated??



    Cheers,
    Steve

  2. #2
    Regular Member GoldenWonder's Avatar
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    Pretty much the same issue I have with mine - although you've done more diagnostic work than me.

    I gave up in the end and assumed it was either a) a charateristic or b) timing chain has slipped a tooth

    Neither of which fills me full of confidence - hence I'm shopping for a 1.8 VVt now, this engine seems way too fragile/sensitive for my liking!

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    Full Member gibbon7000's Avatar
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    Strange as the Z20NET is just about bullet proof and imo one, if not the most reliable of the range.

    My other car. 1972 1641cc slammed beetle. On the road finally!!

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    I don't think a chain that has slipped a tooth would cause erratic idling and nothing else - the valve timing would be wrong at all revs and the engine would feel underpowered to say the least. Plus I haven't yet heard of a Z20NET chain slipping a tooth, just a couple of cases of noisey chains that needed to be replaced.


    Greenmonster - have you tried a good quality full fuel system cleaner?

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    I was thinking more stretched chain altering the cam timing. Also read on a saab forum about broken balancer chain guides on these engines, but then there would be a good deal of noise.

    Yes fuel treatment sound a good idea, but again the car's only done 70k.....

    One thing that was strange was than on the scanner, the engine temperature did not come up on real time data? But it's only got one sensor and the dash gauge works fine as does the cooling fan, so guess it's ok and just sent in the can-bus.

    Anyone had problems with the cam driven vacuum pump, it's a bit tappety?

    Going to have a look at the cam chain with the cam cover off first tomorrow, hopefully see how far out the tensioner pin is, anything else I should check / do?

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    Full Member merikiito's Avatar
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    I would replace the MAF as washing it out with brake fluid would not have been good for it. Should have used proper MAF cleaner which you can get from Halfrauds, bit late now tho . Maybe try one from someone with the same engine.

    might be worth putting some higher octane fuel as well to see if it imporves things
    Last edited by merikiito; 21st June 2012 at 16:03.
    Lois Griffin: Peter! You're bribing your daughter with a car?
    Peter Griffin: Ah, c'mon, Lois, isn't 'bribe' just another word for 'love'?

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    Full Member merikiito's Avatar
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    Vehicle : Insignia CDTi SRi NAV 160

    Trim : SRi

    Engine : A20DTH

    Year : 2009

    Mileage : 88000
    Lois Griffin: Peter! You're bribing your daughter with a car?
    Peter Griffin: Ah, c'mon, Lois, isn't 'bribe' just another word for 'love'?

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    Quote Originally Posted by greenmonster View Post
    Yes fuel treatment sound a good idea, but again the car's only done 70k.....
    If you said the engine has only done 7k, I'd agree that it's a bit early to need a fuel system cleaner. 70k, however, is more than enough mileage for carbon deposits to be partially clogging injectors and sticking to the back of the valves. This would apply even more so if the car has been run extensively on cheaper quality fuel that doesn't have the more advanced detergents in it.

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    Full Member merikiito's Avatar
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    Vehicle : Insignia CDTi SRi NAV 160

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    I would use this http://www.ebay.co.uk/itm/BG44K-BG-4...item519e2e72b9

    Highly recommended by me
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    Peter Griffin: Ah, c'mon, Lois, isn't 'bribe' just another word for 'love'?

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    Personally, i would be checking/replacing ECT sensor (engine coolant temperature), as it sounds like the car is getting wrong input and cant decide if its hot or cold. Did you say you had no reading from it?

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