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Intermittent Engine Shut-off

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Old Jun 12th, 2019, 11:11   #11
aardvarkash10
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Originally Posted by Laird Scooby View Post
You forgot a couple of things Ash - first is LH2.2, same thing can happen on the and second is the first rule of diagnosis.
hoisted by my own petard

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Old Jun 25th, 2019, 19:24   #12
rockaholic
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Thank you all for the great responses. I think it might have been the white relay. I opened her up, cleaned them very dirty contacts and it hasn't misbehaved since. Although, its motorbike season, so not too many km's on the Volvo these days.

But I am prepping the wagon for a long trip to the Balkans so I will check all of those things you have mentioned.

I am still struggling to find the cause for the fluctuating idle speed. It goes up and down by 50 or 100 rpm when idling. MAF cleaned, throttle body cleaned, IAC valve cleaned then replaced with another used one, vacuum leak checked, no luck. The weave is small, but noticeable. Am I too OCD and these cars are meant to be like this, or I am looking in the wrong places? Do I need to check the dizzy-cap? It is a high milage motor - 430,000km - but runs quite good apart from these few issues.

Much appreciated.
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Old Jun 25th, 2019, 21:44   #13
Laird Scooby
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I am still struggling to find the cause for the fluctuating idle speed. It goes up and down by 50 or 100 rpm when idling.
Have you checked that when it's idling the throttle position switch is made?
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Old Jun 26th, 2019, 02:21   #14
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2 simple diagnostic checks you can do say alot.

1. Check for the rpm needle flickering slightly when trying to start (when its not starting). it means you have spark and crank sensor and probably a fuel problem.

2. Listen for the fuel pump priming when turning the ignition on, you need a quiet area to hear it. It means the relay and pump is working.
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Old Jun 26th, 2019, 08:45   #15
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2 simple diagnostic checks you can do say alot.

1. Check for the rpm needle flickering slightly when trying to start (when its not starting). it means you have spark and crank sensor and probably a fuel problem.

2. Listen for the fuel pump priming when turning the ignition on, you need a quiet area to hear it. It means the relay and pump is working.
It would appear to have been the fuel pump relay Tony :

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Thank you all for the great responses. I think it might have been the white relay. I opened her up, cleaned them very dirty contacts and it hasn't misbehaved since.
Hopefully nothing more sinister like a double-headed problem and a potentially dodgy CPS like you allude to.
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Old Jun 26th, 2019, 09:52   #16
Rversteeg
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Default Variation in idle speed

Have you tried idling with the alternator belt removed? It could be a varying load from the alternator. No A/C compressor clutch switching on and off?

As for the fuel pump relay: just replace it for a new one. They are not expensive and it is not just the contacts that get dirty, but also the soldering joints that deteriorate because of the relatively high amperage going through. I just replaced mine for the second time in over 600K km.

BTW: I would not call a 430K km a high milage engine yet, many have done at least 100 or 200K km more.
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Old Jun 28th, 2019, 20:38   #17
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Always have a spare fuel relay. They are over stressed, and overheated. If its not the contacts or the solder the wires break inside the coils.
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