940 LPT 2.3 problems starting in damp

[haymitch]

Cool, I think I'll give that a try - sounds like it's worth a go! Thanks for the continued advice.

ATF seems to have multiple uses. I think I've seen a post where people add this to the oil as part of an oil change too?

[Laird Scooby]

Originally Posted by haymitch

Cool, I think I'll give that a try - sounds like it's worth a go! Thanks for the continued advice.

ATF seems to have multiple uses. I think I've seen a post where people add this to the oil as part of an oil change too?

Probably one of my posts then!

Both my beasts currently have about a litre each of ATF-U in the engine oil, as does my lawnmower and as of today, some in the petrol tank as well.

There is a Rover 820Si in the West Country with about a litre in the engine too, the owner is very happy as it's freed his hydraulic lifters and fixed an oil leak. He is one of the people that tried it in the tank too and has added some to the engine oil in his motorbik and also the petrol tank of his bike. He also recently discovered (2 days ago) that a 99:1 mix of turps:ATF is an excellent electrical contact cleaner, tried it on some contacts that needed cleaning and confirms it's very good for that.

I also mix it 50/50 with acetone for an awesome penetrating fluid and it derusts things too. So far, i haven't yet found the fastener that "WMP" (my name for the 50/50 acetone/ATF-U mix) won't shift.

The synthetic ATFs are better, smaller molecules so they reach places mineral ATF won't get to and retain their properpties longer. I use ATF-U as i had it for the gearbox in my Rover, turns out it meets the spec Toyota/Lexus state for their A341E auto box which is basically an AW71, same as my Volvo. All my experiments with it have some founcdation either on theory or other peoples use of it, So far i haven't found anything it doesn't do, there surely must be something but i suppose if i'm trying it on things i think it might work for then there's a good chance it will if it's based on some sort of theory, however loose.

[haymitch]

Thanks - will give try cleaning the injectors then going from there!

I refitted the IAC hoses again and put clamps on them this evening to ensure they were leak free. Compared to my previous video the car is idling at a lower speed now and is more stable

If I bought the hoses again I'd buy the OEM volvo ones. The silicone ones I bought are fine but they are much more difficult to fit and remove!

[Laird Scooby]

Originally Posted by haymitch

Thanks - will give try cleaning the injectors then going from there!

I refitted the IAC hoses again and put clamps on them this evening to ensure they were leak free. Compared to my previous video the car is idling at a lower speed now and is more stable

Seems like you may have found your air leak! Nothing to lose cleaning the injectors, you might even find some nice side effects like thinking you're a gear lower than you are because of the way it's pulling, better economy and so on.
Let us know how it goes!

[haymitch]

I've had a few interesting symptoms recently that lead me to believe that cleaning the IACV was unsuccessful and my problems are down to a faulty IACV.

The car still has issues when running hot, but the symptoms are slightly different. When started the idle is going up to around 1200 rpm then shifting down to around 600 rpm before evening out at 800 rpm and then being fine in park / neutral. Holding the accelerator down will help it along the way to evening out. Weirdly enough idle from cold has improved. The problem is worse when the car has been left to cool down for about an hour or has been driven the previous day.

I noticed at a junction that if I switch the transmission to drive or reverse then the idle drops down to around 550 - 600 rpm and then only returns to 800 rpm if I select neutral of park. It will start struggle at the lower rpms but not stall. This seems to match symptoms of faulty IACVs I've seen online.

I've also noticed some hesitancy when accelerating from roundabouts. This has been intermittent. I doesn't always happen, but when it does it happens for the entire journey.

Strangely, when I've unplugged entirely the car has started with rpm even lower around 500 rpm, but I've wondering if I have a lazy IACI've had a few interesting symptoms recently that lead me to believe that cleaning the IAC was unsuccessful and my problems are down to a faulty IAC.

The car still has issues when running hot, but the symptoms are slightly different. When started the idle is going up to around 1200 rpm then shifting down to around 600 rpm before evening out at 800 rpm and then being fine in park / neutral. Holding the accelerator down will help it along the way to evening out.

I noticed at a junction that if I switch the transmission to drive or reverse then the idle drops down to around 550 - 600 rpm and then only returns to 800 rpm if I select neutral of park. It will start struggle at the lower rpms but not stall. This seems to match symptoms of the IAC I've seen online.

I've also noticed some hesitancy when accelerating from roundabouts. This has been intermittent. I doesn't always happen, but when it does it happens for the entire journey.

Originally Posted by Laird Scooby

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.

Does anyone have any thoughts on this? Are there any other tests I can do confirm that it is the IACV that is the problem. I've tried plugging and unplugging it and the resistance of it was 8.6 ohms which was okay. An IACV via Skandix looks expensive but I've found a supplier that I can collect from locally.

https://www.gsfcarparts.com/185pc013...ABEgI8YPD_BwE#

I'm starting to add the fuel injector cleaner this week but thought I should mention these symptoms.

[Laird Scooby]

We seem to have gone from one extreme to another - from cold start problems to hot running problems!

If you look under the bonnet at your air cleaner, there is usually a cold air intake that picks up air from near the headlight and a corrugated aluminium hose that feeds the air cleaner with hot air from the exhaust manifold.
Remove the end of this corrugated aluminium hose from the air cleaner and point it somewhere out of the way of the air inlet to the air filter box. See if the hot running/idling symptoms improve.

Usually pulling the aluminium hose off is eased if you twist it as if unscrewing it as well. Doing a bit of digging online for photos to try and show you reveals not all 940s had this, whether the pics are of modified cars or not i don't know. If you have it you should find it easily though.

[haymitch]

I know, it's a strange one - it's driving me crazy because I've fixed the first issue only to be presented with this.

I'll have a look and see if I can find these hoses

[haymitch]

I've taken a look under the air filter box - there is no sign of an aluminium hose. I reckon I must have one of the cars without this

I managed to get myself a copy of the Volvo 940 green book wiring guide and I did some voltage tests on some of the grounds (while cold and while the engine was running). I tested the two grounds at the rear of the engine compartment running from the block, the two grounds near the injectors. These grounds all had the same voltage as between the battery terminals.

I also tested the negative battery terminal to chassis ground and this results in 0V both while the engine was off and running. I tried it again and again but couldn't get any reading. I think this connection or the earth strap might be the culprit, what do you think? It's seems strange that I'd have no other symptoms. I think I'll clean up the ground connection though. I've attached a picture of the ground in question and below the air filter box at the link below:

https://imgur.com/a/6wbsKpC

The car has done the 'hot starting' problem from cold now with the same symptoms. Usually happens when hot though.

[Laird Scooby]

Originally Posted by haymitch

I also tested the negative battery terminal to chassis ground and this results in 0V both while the engine was off and running. I tried it again and again but couldn't get any reading.

That's how it should be. Any voltage read on these tests would indicate a bad connection.

Have you checked the air filter element? Also have you double checked for vacuum hose leaks?

[haymitch]

There was a typo in my email above, when I wrote 'I also tested the negative battery terminal to chassis ground' I meant to say I tested the positive battery terminal to the bolt at the end of the battery - body earth strap. Wouldn't you expect to see the same voltage here as between the battery terminals? Sorry - I'm confused to why the readings from positive to this ground would behave different to positive to other grounds in the engine. For example, with the engine off I measured 12.53V between the positive terminal and the each of the grounds at the rear of the engine bay.

I've checked the air filter I still need to replace the vacuum lines. I'm also going to reread this thread make a list of all the suggestions that have been made in this thread and work through any outstanding ones. For example, I still need to better check your method of engaging the starter once before cranking the engine fully again. I've done this once, but not directly after the hot start problem happens.