940 idle issue. part 69

[Oneeyeblind]

still trying to solve my 1996 2.3t idle problem. it hunts after prolonged full throttle and starts off idling perfect. when its hot though it begins idling a little low.
I managed to make a really really basic code reader and plugged in onto the obd port. (i don't have the handy little diagnostic port thing under the bonnet and no obd scanners can read the codes from the car. kind of stupid system realy.)
The code im getting is 311 which apparently relates to "Signal missing from speedometer"
im assuming thats relating to the pick up from the rear diff? but my confusion is. My speedo works. All the time. Faultlessly. Is it possible it could be sending the correct signal to speedo and the wrong signal to the ECU? I am very confused about this. Could it be my ECU that's toast? (if it was this i would expect a whole list of random errors)

any help hugely appreciated! so fed up with this problem now.

[Forrest]

Have you had the dash out at all? The vehicle speed signal to the ECU is the single wire that comes off what’s usually a double copper electrode on the back if the speedo. You have two wires connected there if you also have cruise control.

It’s easy to leave this wire off when you put the dash back. In my experience it often works OK even when the speedo is being flakey, but that depends why your speedo is playing up.

A more usual sign of missing VSS is high idle that will only reset when you turn the ignition off and back on, but it can affect idle.

Another place to check for a fault is in the multi plug to the ECU, especially if you’ve had any rain leaks in that area.

[Oneeyeblind]

Originally Posted by Forrest

Have you had the dash out at all? The vehicle speed signal to the ECU is the single wire that comes off what’s usually a double copper electrode on the back if the speedo. You have two wires connected there if you also have cruise control.

It’s easy to leave this wire off when you put the dash back. In my experience it often works OK even when the speedo is being flakey, but that depends why your speedo is playing up.

A more usual sign of missing VSS is high idle that will only reset when you turn the ignition off and back on, but it can affect idle.

Another place to check for a fault is in the multi plug to the ECU, especially if you’ve had any rain leaks in that area.

I haven't had the dash out but I have had this problem since I have had the car! if its as simple as this I'm going to vomit.

my car hunts after full throttle but off and on with ignition does fix it straight away... When you say check the multi plug going to the ECU other than a visual check what can I really do with that? should I have continuity between one of the pins and that wire?

thanks so much for your help!
this problem has been a nightmare for me. I have even bit the bullet and sent it to a classic car place that could not find it (they did help themselves to £800 for the pleasure) and a "volvo specialist"

[Volvo_Utrecht]

Just start again with setting idle according to the manual. After so many years many specialist will have used Workarounds to get your car to idle.

My car was idling too low after a drive on the highway as well. Otherwise it was great. After taking the time to set the idle according to the manual (like 500 rpm with the ICV blocked off etc) it now also works properly after a spirited drive

[Oneeyeblind]

Originally Posted by Volvo_Utrecht

Just start again with setting idle according to the manual. After so many years many specialist will have used Workarounds to get your car to idle.

My car was idling too low after a drive on the highway as well. Otherwise it was great. After taking the time to set the idle according to the manual (like 500 rpm with the ICV blocked off etc) it now also works properly after a spirited drive

idle has been set properly.
MAF has been changed
throttle body cleaned ( + new gasket)
IAC changed
its had 3 or 4 carbon cleans
its been smoke tested for any leaks
AND it has a code relating to VVS

its has to be something else or how would off and on fix it

[Forrest]

Removing the dash on a 940 is fairly easy. No need to remove the steering wheel. I think the factory speed signal wire is violet/white. It is the only single connector on the dash. If the car has OEM cruise control there will be a second, similar wire (different colours) connected to the same point. Checking the speedometer end is connected should be trivial.

If that end is connected, then it is also worth checking the multi-plug on the big metal box that will say something like LH-Jetronic on it. I think that is behind the outside driver’s kick panel and not particularly easy to get at. The problem you could have there is corroded pins if any water is leaking in from the outside, possibly via the edge of the windscreen. Pin 34 is the one you’re looking for.

Another thing that might have led to the problem is if a previous owner has changed the instrument cluster for one that isn’t quite the same as the original. Volvo were shockers for having minor differences between otherwise identical looking instruments.

Whatever is causing the 3-1-1 fault it would be a really good idea to try to sort that out before adjusting or replacing anything else given its potential to affect idle. It doesn’t set the engine warning light so you’ll have to check/reset it with your code-reader.

Probably also worth Googling things like “Volvo 940 3-1-1” and “LH2.4 VSS” to find a whole wealth of past information out there.

Good luck getting to the bottom of it.

[Forrest]

The speed signal wire to the ECU and cruise control if fitted connect to this terminal.

[Oneeyeblind]

Originally Posted by Forrest

The speed signal wire to the ECU and cruise control if fitted connect to this terminal.

Pulled the dash off today at work and to my horror. The wire was connected!!!
Probably not going to get a chance to have another play with it until Saturday unfortunately but I'm hopeful that maybe the wire is broken along the line somewhere? Will throw up in my mouth if its a nice simple fix like that.
If not I will look at possibly getting my ECU checked by someone. Does anybody know of any places in the UK that would be able to check it once removed?
Possibly the dash aswell?
I'm not Afraid of chucking money into this problem and just want it fixed as I'm road tripping to Switzerland in a few months and the Mrs insists on us driving her Hyundai i20 if I can't get it sorted (yuck)

[Oneeyeblind]

Originally Posted by Forrest

Removing the dash on a 940 is fairly easy. No need to remove the steering wheel. I think the factory speed signal wire is violet/white. It is the only single connector on the dash. If the car has OEM cruise control there will be a second, similar wire (different colours) connected to the same point. Checking the speedometer end is connected should be trivial.

If that end is connected, then it is also worth checking the multi-plug on the big metal box that will say something like LH-Jetronic on it. I think that is behind the outside driver’s kick panel and not particularly easy to get at. The problem you could have there is corroded pins if any water is leaking in from the outside, possibly via the edge of the windscreen. Pin 34 is the one you’re looking for.

Another thing that might have led to the problem is if a previous owner has changed the instrument cluster for one that isn’t quite the same as the original. Volvo were shockers for having minor differences between otherwise identical looking instruments.

Whatever is causing the 3-1-1 fault it would be a really good idea to try to sort that out before adjusting or replacing anything else given its potential to affect idle. It doesn’t set the engine warning light so you’ll have to check/reset it with your code-reader.

Probably also worth Googling things like “Volvo 940 3-1-1” and “LH2.4 VSS” to find a whole wealth of past information out there.

Good luck getting to the bottom of it.

its finally fixed. ive had this problem since ive owned the car and its realy been ruining the experience for me.
ive made countless posts over it and done hours of research trying to get it sorted. The problem was the tiny screw was missing that goes into the back of the dash and connects the loop to the two prong terminal.

i owe you a drink mate.

[360beast]

Originally Posted by Oneeyeblind

its finally fixed. ive had this problem since ive owned the car and its realy been ruining the experience for me.
ive made countless posts over it and done hours of research trying to get it sorted. The problem was the tiny screw was missing that goes into the back of the dash and connects the loop to the two prong terminal.

i owe you a drink mate.

Bloody good job there, you seriously preserved with this one!

I believe the seller was probably telling your porky pies then when he said it never did it when he had it!