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Author Topic: Idling issue.  (Read 573 times)

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05omegav6

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Idling issue.
« on: 06 April 2011, 20:37:07 »

Following on from previous saga:

Car has now had 6 new spark plugs, two coil packs, a new non return valve on the main vac line, all the inlet and plenum gaskets renewed, breathers cleaned again and finally a new MAF sensor.

Engine now idles steadily at 550 rpm, temp 85, with the faintest hint of a misfire on one cylinder, (guessing pot 6 ::)).

BUT as soon as the fan kicks in at 92 degrees, the engine knocks and starts hunting between 500rpm and 675ish rpm, and runs really roughly. :-/

As soon as the fan switches off, normal service is resumed. I've left the engine idling for about 20 mins and EVERY time the fan kicks in it starts p#ssing about. >:(

At least it is now doing something consistently. :-/

Any thoughts (except binning it :-X) appreciated,

Al. :y
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Entwood

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Re: Idling issue.
« Reply #1 on: 06 April 2011, 20:40:56 »

Somewhere in the maintainance guide is Kevin Wood's excellent guide to battery/alternator checking .. might be worth doing that ??

Seems to me the poor running occurs under high current conditions .. could be a voltage problem that is upsetting the ECU ???

You could try switching headlights on/off and seeing if that affects the running ???

Clutching at straws I know .. but high load seems to be a common factor ??
« Last Edit: 06 April 2011, 20:41:35 by entwood »
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Abiton

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Re: Idling issue.
« Reply #2 on: 06 April 2011, 21:11:12 »

^^^ That's what I was about to say.

However, I have another idea that may be worth a look.  Could the hot air from the fan be causing a split/crack in some air hose to open up more with thermal expansion?  I believe on the V6s there's some prime candidate air hoses right between rad and throttle bodies...

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Peter13

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Re: Idling issue.
« Reply #3 on: 06 April 2011, 21:24:57 »

It would worth to see live data if possible.
I would also get a brake or carb cleaner spray and do a quick check for vacuum leaks.

Btw how dis you measure 550rpm, by your eyes on the dash?
Mine was 750@OBD when I saw ~550rpm@dash, and also had a dip(but only for a few seconds) when the vent started.
I have just posted few hours ago that replacing the ECU solved both! (rpm is now 600, which looks 450 on  the dashboard)
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05omegav6

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Re: Idling issue.
« Reply #4 on: 06 April 2011, 22:43:00 »

Quote
Posted by: Entwood      Posted on: Today at 20:40
Somewhere in the maintainance guide is Kevin Wood's excellent guide to battery/alternator checking .. might be worth doing that ??

Seems to me the poor running occurs under high current conditions .. could be a voltage problem that is upsetting the ECU ???

You could try switching headlights on/off and seeing if that affects the running ???

Clutching at straws I know .. but high load seems to be a common factor ??

I shall do that as soon as I can find my multi meter ::) a cursory check of the terminals suggests that they are in order; no fraying, vaguely warm to touch (engine running, lights and blower on).

No problems starting the car either, always first attempt, usually firing as soon as the key hits 3.

Car idles at 700rpm on start, then drops to 550 once warm, lights and blower do seem to make the idle worse. Emissions light is on constantly and flashes periodically.

Will re count codes tomorrow, eyes tired today, but seem to get the following:

0430, bank 2 precat. Probably got some plug electrode stuck in it. ::)
0300, multiple random missfire. Not surprising if hunting around :-/
0304, missfire pot 4  :-/
0305, misfire pot 5  :-/
0306, misfire pot 6 Not surprised having destroyed previous plug. :-/
0110, air intake temp voltage hi/lo. Not sure on this one.
1111, air intake valve 2 voltage hi/lo/open. Front multiram wasn't securely plugged in. ::)
         (I'd removed the ducting to move radiator back in order to swap the condenser over).

Not sure where the previous codes have gone, not showing with pedal trick. :-/

Rpms are read from dash.
« Last Edit: 06 April 2011, 22:44:30 by 05omegav6 »
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Kevin Wood

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Re: Idling issue.
« Reply #5 on: 07 April 2011, 12:19:46 »

Sounds very much like electrical load is either causing a large voltage drop or is interfering with the values reported by one of more sensors.

I would check the ground connections between battery, engine block and chassis and also, as suggested, see what the battery voltage is doing when the fans kick in.

Kevin
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Kevin Wood

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Re: Idling issue.
« Reply #6 on: 07 April 2011, 12:21:49 »

IIRC yours has an ex-plod battery master switch fitted?

Might be worth eliminating this. I have seen them go high resistance in the past. Just put a multimeter across it on volts and see if it's dropping anything significant when under load.

Kevin
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05omegav6

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Re: Idling issue.
« Reply #7 on: 08 April 2011, 06:28:54 »

Quote
IIRC yours has an ex-plod battery master switch fitted?

Might be worth eliminating this. I have seen them go high resistance in the past. Just put a multimeter across it on volts and see if it's dropping anything significant when under load.

Kevin

Consider this eliminated. :y It is no longer attached to the car.

Having disconnected the battery, removed said switch, rejoined original loom and reconnected the battery, the car started first turn, idled smoothly and even the emissions light went out :y

The gradually as the car warmed up it started to hunt a bit, the emissions light flashed maybe 15 times, the went out. :-/

Long story short it is now hunting alot, emissions light is on permanently again >:( and to top it off I still can't find my multimeter so will have to buy another to replace it >:(

Rhetorical question: Does any one own a well behaved sensible Omega, or is such a thing a mythical beast lost in the sands of time? :-/
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Abiton

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Re: Idling issue.
« Reply #8 on: 08 April 2011, 07:56:07 »

Checked that inlet trunking yet, on the way to the throttle bodies?
Perahps the hunting has got worse 'cos the crack's got bigger?

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Kevin Wood

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Re: Idling issue.
« Reply #9 on: 08 April 2011, 09:35:39 »

If the rough running is still cooling fan / electrical load related, the only likely possibility is that it's dragging down a supply somewhere, or dragging up a ground point. Fans and engine ECU are only connected by their power supply.  :-/

Kevin
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kcl

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Re: Idling issue.
« Reply #10 on: 08 April 2011, 13:16:49 »

Quote
Quote
IIRC yours has an ex-plod battery master switch fitted?

Might be worth eliminating this. I have seen them go high resistance in the past. Just put a multimeter across it on volts and see if it's dropping anything significant when under load.

Kevin

Consider this eliminated. :y It is no longer attached to the car.

Having disconnected the battery, removed said switch, rejoined original loom and reconnected the battery, the car started first turn, idled smoothly and even the emissions light went out :y

The gradually as the car warmed up it started to hunt a bit, the emissions light flashed maybe 15 times, the went out. :-/

Long story short it is now hunting alot, emissions light is on permanently again >:( and to top it off I still can't find my multimeter so will have to buy another to replace it >:(

Rhetorical question: Does any one own a well behaved sensible Omega, or is such a thing a mythical beast lost in the sands of time? :-/


Given that you have the code 0110 and it starts hunting when warming I'd confirm that the engine temp sender is working ok  :-/ Dunno if you can measure it with a multimeter but not that expensive to replace the sender.
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