S40 2.0 Petrol 2011 - rough idle

[ajguk]

Hi all

So new to me 74K mile S40 has something of a rough idle, feels like a diesel through the steering wheel. Not what I would describe as 'lumpy' i.e. revs are settled around 1K rpm, not bouncing around all over the place.

What are the first things I should be looking at? Would cleaning the throttle body out be a good place to start or shall I go straight to spark plugs and coil packs? It's a winter 'shed' but is in generally good nick, but would like to start off cheap if possible!

Thanks

[Brione]

Hi I had similar problems with my 2.0d V50. Idle was smooth but you could feel the car shudder slightly and a vibration through steering wheel. I replaced all 3 engine mounts and problems went away. Not sure if this is your problem but It could be a starting point? All three mounts were less than £100 and I done it on the drive way in just over an hour.

Cheers

Brione

[ajguk]

Yes I've seen this mentioned actually so could be worth a try. How easy is the access on these engines?

[PNM]

The plugs are due changing at 75k, so it might be worth doing them too, although the mounts is the more likely source of the problem.

[Clan]

Originally Posted by ajguk

Hi all

So new to me 74K mile S40 has something of a rough idle, feels like a diesel through the steering wheel. Not what I would describe as 'lumpy' i.e. revs are settled around 1K rpm, not bouncing around all over the place.

What are the first things I should be looking at? Would cleaning the throttle body out be a good place to start or shall I go straight to spark plugs and coil packs? It's a winter 'shed' but is in generally good nick, but would like to start off cheap if possible!

Thanks

could be oil around the plugs or a coil failed or neglected spark plugs

[Brione]

Originally Posted by ajguk

Yes I've seen this mentioned actually so could be worth a try. How easy is the access on these engines?

Not sure if the same on the petrol. But on the diesel was easy enough. The driver's side mount was the easiest. Just support the engine, I used a block of wood under the sump on a trolley jack. Only 4 bolts. Passenger side mount was under the battery. So all the enclosure for that had to be removed but still simple enough. I just supported the engine in the same way with block under the gearbox. The torque mount was a pain though. But managed to get it out by putting car on small ramps and lying under car and was able to wiggle it free pushing the engine forward and fitting in reverse. You could maybe just leave this one though. If your gear change is smooth it is probably ok. I'd start with the driver's side. It is the most substantial and could be the main cause of the problem. This is supposed to fit your car. https://www.ebay.co.uk/itm/384170745...gAAOSwOFBgozCw . Look to see if you see similar on yours and that's a start for you?

Cheers

Brione

[ajguk]

Originally Posted by Brione

Not sure if the same on the petrol. But on the diesel was easy enough. The driver's side mount was the easiest. Just support the engine, I used a block of wood under the sump on a trolley jack. Only 4 bolts. Passenger side mount was under the battery. So all the enclosure for that had to be removed but still simple enough. I just supported the engine in the same way with block under the gearbox. The torque mount was a pain though. But managed to get it out by putting car on small ramps and lying under car and was able to wiggle it free pushing the engine forward and fitting in reverse. You could maybe just leave this one though. If your gear change is smooth it is probably ok. I'd start with the driver's side. It is the most substantial and could be the main cause of the problem. This is supposed to fit your car. https://www.ebay.co.uk/itm/384170745...gAAOSwOFBgozCw . Look to see if you see similar on yours and that's a start for you?

Cheers

Brione

Thanks Brione. I had a look at the weekend and the driver's side mount was easily visible, and I can see quite a bit of perished rubber on there. I think it's a job for next week when I've got a few days off, thanks for the instructions, I will give it a try! Might do the plugs as someone else has suggested too, and possibly get hold of a coil pack and try it on each cylinder. Takes me back to when I had a Mazda3 MPS and was chasing down a misfire!

Something else that has alerted me a bit as well is that I've got a failed ambient temp sensor, it thinks the temp is about 12 degress lower than it actually is. An old post suggests that this sensor supplies the ECU so the car may think it's colder than it is, causing under/over fuelling which can affect the engine and particularly the mpg (which according to the onboard is around 27mpg at the moment, I mainly do shortish journeys though so this doesn't seem that bad).

Thanks

[ajguk]

Originally Posted by PNM

The plugs are due changing at 75k, so it might be worth doing them too, although the mounts is the more likely source of the problem.

I'll check the latest service entries and see when they were last done (if ever), thanks.

[andy_d]

Originally Posted by ajguk

Thanks Brione. I had a look at the weekend and the driver's side mount was easily visible, and I can see quite a bit of perished rubber on there. I think it's a job for next week when I've got a few days off, thanks for the instructions, I will give it a try! Might do the plugs as someone else has suggested too, and possibly get hold of a coil pack and try it on each cylinder. Takes me back to when I had a Mazda3 MPS and was chasing down a misfire!

Something else that has alerted me a bit as well is that I've got a failed ambient temp sensor, it thinks the temp is about 12 degress lower than it actually is. An old post suggests that this sensor supplies the ECU so the car may think it's colder than it is, causing under/over fuelling which can affect the engine and particularly the mpg (which according to the onboard is around 27mpg at the moment, I mainly do shortish journeys though so this doesn't seem that bad).

Thanks

passenger side door mirror is where that is,, cheap part from a main dealer,
easy fit,
door card off,
tweeter cover off
disconnect door mirror leads,
unbolt door mirror
remove glass,
access temp sensor + housing,,
swap
rebuild

[ajguk]

Originally Posted by ajguk

I'll check the latest service entries and see when they were last done (if ever), thanks.

These were only changed last year actually, only 3K miles ago. I'll get the temp sensor done then move onto the engine mounts.