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Ecotec missing just of idle

Bugsy27

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I have a VT series 2 and it has this annoying miss or stumble just off idle. Start the car and it idles perfectly smooth. touch the throttle in gear or in neutral and its starts missing and stumbling till revs are up to round 17-1800 then shes fine again. Anyone got any ideas where to start?
 

someguy360

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I have found over the years that hesitation or missfire just off idle (e.g just applying the throttle from idle) is usually injectors.

But just in case start with the cheapest things first....plugs and leads
 

Bugsy27

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Okay cheers, Ive got some new plugs and another set of leads here so I'll try that and see how it goes
 

Guan0

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Under steering wheel under the drop-down fusebox cover thingy on the outside

There's a plug, With key in off postion. get a paperclip and connect 5 & 6 together (from top row, left to right)
When 5&6 are connected, get a pen and paper to writedown numbers
turn your "Reds" ON
Now count the flashes of the "Check Engine Light" to get error codes
It signals like this "Flash, pause , pause, Flash"
1st the Tens unit in code (e.g. 5 flashes = 5X Fifty)
2nd the ones unit in code (e.g. 7 flashes =X7 seven)
So 5 & 7 = 57 Injector Power Supply Voltage Variation
It REPEATS codes three(3) times
1st code WILL be 12 (normal state code)
E.g. 5flash 7flash - 5flash 7flash - 5flash 7flash - NEXT CODE (if no more then back to start code 12)
Had this prob twice
1st time NO ERROR Codes
It was the fuel pump
Rev it in park till it redlines
If u cant reach 5000rpm its fuel pump
Second time idling at 800rpm & choking at 13-1500rpm
Codes 35 & 48
35:- idle speed error (19,21 & 22 are Idle Postion sensor errors)
48:- Cam Angle Sensor

I put 2ndhand Idle throttle sensor and camshaft sensor in
Sort-of fixed it, it idles rights but it started choking at 2300rpm instead
And would start 1st time every time no dead 2nd keyturn
I didnt do PCM idle reset as service manual says to do, as correct idle was restored by replacing idle Throttle Sensor
I had other issues though too 31 & 92 which together for me meant PCM was stuffed
Went to wreackers Replaced both BCM & PCM need both as their linked cost $$$ to pair different ones together
No probs now

Hope it helps in some way
 

Bugsy27

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Okay an update on problem. Today i fitted new plugs, new leads, another set of coils, cleaned AFM and throttle body, and cleaned idle control valve. Problem is still there. Idles perfectly but just off idle it misses, on the road coasting along at 50kms the motor is missing and surging, but give it a bit of throttle and it performs perfectly. I havent done the paperclip test yet but hope too tomorrow...Any more ideas...
 

SavVYute

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A faulty throttle position sensor could cause those symptoms.
 

Bugsy27

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Okay. Thanks for that, I'll try to locate one today, and I'll try the paperclip test this afternoon before I change the TPS. Cheers for that
 

Bugsy27

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Okay guys just a follow up. Replaced the throttle position sensor and reset the base idle and its running perfectly now.
Thanks for the help guys, saved me some headaches.
 

Bugsy27

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Further update, ran it again later today and its started doing it again. Cruising at 50-60 kms just touching the throttle, you can feel the car surging and backing off just continually cycling surge and off, give it a little more throttle and goes brilliant...Pain in the arse bl***y car
 

Brett_jjj

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Did you do the paperclip test mentioned above? It will probably show whats wrong with it. Its one of the first things that should be done when diagnosing running problems on these vehicels.
 
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