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Author Topic: Lumpy idle and stalling  (Read 493 times)

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Undiscovered

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Lumpy idle and stalling
« on: 06 August 2019, 12:10:39 »

I have an Omega, 3L V6 Auto. W plate 2000reg.
Lpg converted.

Fortnight or so ago, it stalled while in a car park, looking for a space (tick over revs, low speed). Fired back up immediately. Switched it to petrol, no issues.

Later on that day, stalled again, em light lit, wouldn't fire. Waited 10-15 mins, fired up. Sounded rough, like crap in fuel so got gallon of petrol in it- usually run it on quarter tank as lpg.

Fired up sounded fine. Pulled off drive, stalled. em light lit.
Mate reckoned crank sensor. Garage diagnosed n replaced crank sensor. Couldn't recreate fault.

Picked it up yesterday. Sounded sweet, drove fine. Got home, stalled on drive. Lumpy idle.
Ticks over at 500rpm, then stalls. Starts up straight away, then 30s later, stalls. Em light lit. Repeat twice, then fine. If I rev it, seems fine. Not moved it from driveway as it was a bugger to push home last time.
I'll post the paperclip trick diagnostics tonight.

Any ideas? I'm on holiday in a fortnight n really need the car!
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Migv6 le Frog Fan

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Re: Lumpy idle and stalling
« Reply #1 on: 06 August 2019, 12:34:28 »

So the problem only occurs on LPG and its fine on petrol ? If it happens on both first action would be to clean out the idle control valve - sits on the o/s of the plenum. Clean out with carb cleaner, petrol or similar. Then a few drops of light oil dropped into it to prevent it becoming sticky.
If its an LPG only problem, there are a few experts on here, but you might have to wait a while for them to pop up and offer advice.
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terry paget

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Re: Lumpy idle and stalling
« Reply #2 on: 06 August 2019, 12:46:33 »

Could be MAF (mass air flow) sensor. Easy to check, unplug it and drive the car. EML will be on, but if it cures the fault, you will have found what's wrong.

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Re: Lumpy idle and stalling
« Reply #3 on: 06 August 2019, 12:49:19 »

Problem initially happened on lpg, so switched it to run on petrol and kept it on petrol since.
It runs on petrol at startup before autoswitching, when enabled, to lpg.

It takes awhile to switch to LPG when idling, and I don't want to be doing further damage to the engine in that time.
It was my LPG fitter who said crank sensor issues.

Will try mass air flow sensor later on too. It almost feels if the car is hunting before it stalls.
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Doctor Gollum

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Re: Lumpy idle and stalling
« Reply #4 on: 06 August 2019, 14:55:04 »

A non genuine crank sensor, from a non genuine supplier that you didn't walk into will work once. Might last a week, or possibly even a year, but ultimately it will be a waste of money :'(
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Raeturbo

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Re: Lumpy idle and stalling
« Reply #5 on: 06 August 2019, 15:04:42 »

Will it run ok on petroleum?
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Re: Lumpy idle and stalling
« Reply #6 on: 06 August 2019, 15:41:32 »

Paper clip it and report back :y

Crank sensor code is normal when not running, so might lead someone unfamiliar with the Omega to conclude it is faulty ;)
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Re: Lumpy idle and stalling
« Reply #7 on: 06 August 2019, 20:31:11 »

Ignition on and running, both show code 19. Incorrect rpm signal.
When revs drop to 5-600, it's normal idle speed, cuts out.

With maf sensor unplugged, car seems less lumpy, still shows code 19 and cuts out at the same rpm.

Any ideas.
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Re: Lumpy idle and stalling
« Reply #8 on: 06 August 2019, 20:41:17 »

Got an assistant to give it rev while I had a look about under the bonnet- there's a persistent ticking from the rear offside cylinder.
Thinking a misfire?
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Re: Lumpy idle and stalling
« Reply #9 on: 06 August 2019, 21:16:02 »

From looking through the forum, seems could be still the crank sensor, either worn wiring or non-GM part.
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Migv6 le Frog Fan

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Re: Lumpy idle and stalling
« Reply #10 on: 06 August 2019, 23:37:42 »

Idle control valve
Crank sensor
Dispack rusted causing misfire
Dispack and/ or plug leads fried due to oil in plug wells, from leaking camcover gaskets
MAF sensor......
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Re: Lumpy idle and stalling
« Reply #11 on: 07 August 2019, 02:15:52 »

Plugs or leads first off :y

Lpg is far less tolerant of weak spark...

Pull the plugs and report back :y
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Re: Lumpy idle and stalling
« Reply #12 on: 07 August 2019, 02:38:14 »

Ignition on and running, both show code 19. Incorrect rpm signal.
When revs drop to 5-600, it's normal idle speed, cuts out.

With maf sensor unplugged, car seems less lumpy, still shows code 19 and cuts out at the same rpm.

Any ideas.
Fault code 19 with ignition on and also when engine running indicates that the crank sensor is (still) bad.
You should see code 31 with ignition on and this should disappear when the engine is started. 31 = no rpm signal.

It might be that the garage have fitted an incorrect type of sensor for your engine/ECU combination. Where did they get the replacement from? Did they give you back the old sensor? Look at the head.

Assuming your old sensor was a Bosch with an oval sided plug then you need  GM 90540743 which will be marked GM & Bosch 0 261 210 131.
The other sensor with the same cable and oval sided plug that's made by Delphi or Siemens won't work properly even though it fits perfectly. It has lower resistance.

Sort the crank sensor first.
« Last Edit: 07 August 2019, 02:44:37 by Enceladus »
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Re: Lumpy idle and stalling
« Reply #13 on: 07 August 2019, 03:49:29 »

I'll check the sensor when I get back from work later. From what I can gather, it should be on the front of the engine.
Vehicle had new plugs, and had a leaky cam cover replaced 2months back and has been fine on both LPG and petrol, though this is something to consider.
 All of these problems are when running on petrol- as long as it goes, I can get away on holiday!
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BazaJT

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Re: Lumpy idle and stalling
« Reply #14 on: 07 August 2019, 07:51:51 »

Crank sensor is at side of oil filter[engine end]with electrical plug behind nearside cylinder head,front of engine are the cam sensors.
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