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Slightly annoying idle speed 1000rpm

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Old Feb 19th, 2021, 14:40   #11
Rversteeg
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Default Lambda sensor

I recently replaced my lambda sensor after at least 300K miles, but it could very well have been the original one, so in taht case add another 100K miles. I have always been running it on LPG which is quite soft on the sensor, but even then, there would not have been much life left in it. It runs a bit smoother now, but I didn't notice any change in idling behaviour before or after.

I do not think the PAS will have an influence, as the ECU would compensate for the additional resistance after it has seen a speed drop below 850 rpm (closed throttle (TPS) and zero speed), not on beforehand. The only additional loads it compensates for on beforehand are the AC engage signal, E-fan engage signal and auto gearbox not in P signal. But as you grounded the applicable pins of the LH you are apperently aware of that.

What I did notice however, is that when the car has been driven off with a cold engine and only stopped for the first time after the engine is fully warmed up, the re-adjusting of the idle speed takes several seconds of standstill. If the period in between has been more than say 20 minutes or so, it sometimes happens that the idle speed is not controlled back properly, but remains at high idle. It then helps to strangle the engine to less than idle, after which the idle speed control is reset and works fine again.
What happens if you strangle the engine a bit when it is running at high idle?

Rob
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Old Feb 19th, 2021, 14:51   #12
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That confirms what i said about LH keeping the idle speed high Rob, also you should change your Lambda sensor a bit more often - the accepted lifespan is 100k miles or 10 years and pull fuse #1 to reset the ECU fuel trims after fitting to get the best results.

Note about the PAS - if the rack isn't in the central position when the steering wheel is in the straight ahead position, this will open one or other of the spool valves in the rack to provide assistance in the direction it thinks the rack is moving. This puts the pump under more pressure which creates heat in the fluid so it bols and creates ari pockets which lead to cavitation in the pump which puts more load on the pump drive and hence the engine. Once the fluid boils, it expands and will find its way out through the breather cap either on the pump if it's integral or later on the remote reservoir - the extra capacity of the remote reservoir versions gives a bit more fluid to be heated up before it gets to that point though.
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Old Feb 19th, 2021, 16:44   #13
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Is this a turbo, and does it have a working speedometer?

When 2.3 turbo redblock swapping my 340, we found the engine would idle high after the engine had been on boost. Giving the ECU a speed signal solved that
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Old Feb 19th, 2021, 18:58   #14
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Thanks for the replies. Theres a bit of info to digest and i dont think i can work on my car untill the weekend after this one.
FYI its a 96 940 b230fk m90. Speedo and cruise control work ok. Both my original and the swapped lambda were 130-140k likely original units. (My drawer only grows crusty old parts with about 130k miles on them already, but does come in handy). Volvo quoted me 150+ for new! Are generic ones normally ok? I will test mine, im assuming i can just probe the back of the plug in the bay. The ect sensor replaced was a new bosch unit, closest to the rear of the motor. I rebuilt the head in the summer so the inlet gaskets are all fresh, all the hoses and seals are new. Ive pinched off all vac lines from the mani and sprayed easystart over it all but rpm stays high.
Rob, i will strangle my engine and report back.

Last edited by sonofturd; Feb 19th, 2021 at 19:02.
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Old Feb 19th, 2021, 20:59   #15
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Quote:
Originally Posted by sonofturd View Post
Thanks for the replies. Theres a bit of info to digest and i dont think i can work on my car untill the weekend after this one.
FYI its a 96 940 b230fk m90. Speedo and cruise control work ok. Both my original and the swapped lambda were 130-140k likely original units. (My drawer only grows crusty old parts with about 130k miles on them already, but does come in handy). Volvo quoted me 150+ for new! Are generic ones normally ok? I will test mine, im assuming i can just probe the back of the plug in the bay. The ect sensor replaced was a new bosch unit, closest to the rear of the motor. I rebuilt the head in the summer so the inlet gaskets are all fresh, all the hoses and seals are new. Ive pinched off all vac lines from the mani and sprayed easystart over it all but rpm stays high.
Rob, i will strangle my engine and report back.
Do you know the Bosch number of your original Lambda sensor? Should be 0 258 003 381, You can get generic ones but some are supplied with three butt-splice crimps, others have a proper plug on for plug'n'play. Usually the latter is more expensive (but not much) and is worth the extra for having the reliability of a proper plug rather than those horrible butt-splices.

Just looked on fleabay :

https://www.ebay.co.uk/itm/VOLVO-940...0/114266609582

When you fit it, pull fuse #1 for 30 seconds or longer to reset the ECUs fuel trims and DTC memory.
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Old Feb 21st, 2021, 21:20   #16
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Mines got the brown connection. Just checked its a bosch one and likely original as it also has the volvo number on it.
Bosch number is 0258003376
Looking like 80. Hoping mine tests out ok.
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Old Feb 21st, 2021, 21:43   #17
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Quote:
Originally Posted by sonofturd View Post
Mines got the brown connection. Just checked its a bosch one and likely original as it also has the volvo number on it.
Bosch number is 0258003376
Looking like 80. Hoping mine tests out ok.
That would be 0 258 003 378 then. Makes your car a 94-95 940 with a B230FD engine in it.

http://www.myvolvolibrary.info/Tech_...DataPocket.pdf

Page 19 of that pdf shows them all.

If it is original, it's well worth renewing it (pull fuse #1 before you start and refit after) as the chances are it's well past its best. Usual lifespan is 100k miles or 10 years, using secondhand is a false economy as the shock of freeing them from where they've been sat usually damages them - might work for a while but fail soon after and even then, a second hand one is an unknown quantity anyway.
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Old Feb 23rd, 2021, 14:23   #18
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The PM system is playing up again, won't let me reply. If you have a pdf reader (Adobe Acrobat or similar) or use Firefox the link should work, works for me anyway.

The p/No you quoted relates to the Lambda sensor for a 94-95 940 with a B230FD so isn't the right sensor for your car. That said, i doubt there's much difference electrically as long as the pinouts are the same.

The correct sensor for yours (now you've shared it's a 96 B230FK) is an 0 258 003 381, Volvo P/No 91 35 794 or alternatively, Volvo P/No 91 35 621, Bosch 0 258 003 384, either way subject to you checking the plug is correct, this one should be right :

https://www.ebay.co.uk/itm/VOLVO-940...0/114266609582

Pull fuse #1 before fitting and refit after. It may or may not be your problem though, the fact you've got various mods on your engine could be throwing things out more than somewhat.
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