940 LPT 2.3 problems starting in damp

[Laird Scooby]

Originally Posted by Spacebar

You tried the coolant temperature sensor? My car wouldn't start in the mornings when it was colder without a few minutes of cranking whilst pressing the accelerator. Once started it spluttered and wouldn't rev past 3000rpm, when warmed up it ran pretty much like normal. A new coolant temperature sensor cured it

Originally Posted by Bugjam1999

^this.

Replace the ecu temp sensor with a Bosch one.

Cheers

Originally Posted by Bugjam1999

https://www.volvoforums.org.uk/showthread.php?t=288891

Cheers

The CTS was renewed a few months back and didn't appear to improve matters. Whether with a Bosch or not is another matter and it is something on the list to eliminate.

First we need to eliminate the less obvious "jump to conclusion" items that may have had undocumented fiddling in the past. I'm thinking a lazy AICV and some idiot has compensated by altering the base idle position of the throttle butterfly and not only screwed things up because of that but didn't bother resetting the TPS so the engine knows when it's meant to be idling.

Hence the question about manual or auto - i have a simple test in mind that is easier with a manual but can be carried out slightly differently with an auto. It will determine whether the AICV is operating or not.

[haymitch]

The car is an automatic

Thanks for highlighting the coolant temperature sensor - one item on the list is buying a bosch sensor to try replacing it. I've watched some YouTube videos and reckon I can handle the replacement. The only thing I'm worrying about is getting coolant everywhere because I have no driveway and the car is parked on a public road, but I suppose I can have a bucket of water handy!

Thinking about previous fiddling that may have done something wrong to the car and the mention of the breathers being blocked. I had the PCV system cleaned out about about a week before these problems started. I don't know whether the mechanic could have dislodged something causing some kind of vacuum leak? He mentioned that the pipes attached to the crankcase breather box were hard and showing their age.

[loki_the_glt]

Originally Posted by haymitch

The car is an automatic

Thanks for highlighting the coolant temperature sensor - one item on the list is buying a bosch sensor to try replacing it. I've watched some YouTube videos and reckon I can handle the replacement. The only thing I'm worrying about is getting coolant everywhere because I have no driveway and the car is parked on a public road, but I suppose I can have a bucket of water handy!

The CTS is easy to do once you've removed the inlet manifold, so pick up a new manifold gasket. Rumour has it that you can remove and replace it with the manifold in situ but I haven't got sufficiently strong and small fingers and/or ratchet spanners to attempt it!

There's not much coolant loss if the engine's stone cold; you'd probably lose more from the manifold than the sensor socket.

[Laird Scooby]

Originally Posted by haymitch

The car is an automatic


Thinking about previous fiddling that may have done something wrong to the car and the mention of the breathers being blocked. I had the PCV system cleaned out about about a week before these problems started. I don't know whether the mechanic could have dislodged something causing some kind of vacuum leak? He mentioned that the pipes attached to the crankcase breather box were hard and showing their age.

That is a very likely scenario! It could even be the fault.

Meanwhile with the things we can check easily enough, do you have qa hill you can reverse up reasonably safely without some numpty come screaming down it at 90mph while you're trying to reverse?

If so, get the engine warm and if thee's a flat lead up to the hill, start there.

Engine idling, take a note of the rpm in "N" or "P", now select "R" and note what it drops to. Let go of the footbrake and let the car start to creep backwards up the hill. As the extra load of the hill goes on, the revs should start to drop a little but the AICV should compensate and keep the revs more or less as they were when you first engaged reverse.

Don't touch the throttle thourghout any of this.

Take notes of the minimum the rpm drops to while reversing and also the minimum steady reading.

Sounds kind of weird but will be an enormous help in pinpointing what i think it might be.

[haymitch]

How a steep a hill would I need? I live in a village on the edge of the fens so that might be difficult! I'll see if I can think of a hill though

[Laird Scooby]

Originally Posted by haymitch

How a steep a hill would I need? I live in a village on the edge of the fens so that might be difficult! I'll see if I can think of a hill though

I wasn't sure where you lived but i know it's fairly flat round here. An alternative would be to gently pull the handbrake on gradually and do the test on flat ground. Wouldn't need much of a hill though.

[haymitch]

Okay, no problem. Will give that a go!

[Stephen Edwin]

Seven characters.

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[Bugjam1999]

Originally Posted by loki_the_glt

The CTS is easy to do once you've removed the inlet manifold, so pick up a new manifold gasket. Rumour has it that you can remove and replace it with the manifold in situ but I haven't got sufficiently strong and small fingers and/or ratchet spanners to attempt it!

There's not much coolant loss if the engine's stone cold; you'd probably lose more from the manifold than the sensor socket.

There’s no need to remove the inlet manifold. An appropriately sized socket fits over the sensor and with an extension and perhaps a wobble joint it’s easy to undo. I think I moved some wiring to one side and perhaps the pipe coming out of the top of the oil separator box, but it’s certainly not a difficult job.

To remove some coolant put a suitable container under the brass drain **** on the rear right side of the engine and drain a bit. Easy to reach, 13mm spanner.

Cheers

[Bugjam1999]

OP- do you have a code reader? I highly recommend making one. One of the three diagnostic modes is the test cycling of moving components, one of which is the idle air control valve, so you could see if it is working properly.

Cheers