00 VR: shuddering, sputtering when hot at idle

[sanfelice]

I just replaced the plugs which were really *bad* and the problem went away for 50 miles, but just today the shuddering returned as I was in traffic. I did have the AC on for a bit but I'm not sure that had much to do with it. I turned the AC off and it still was shuddering.

The car drives just fine when RPM are applied, so I don't suspect fuel although I suppose it could be. The other reason to *not* suspect fuel is that I smell the unburned fuel after this occurs.

Other than ignition, any ideas?

Shall I test for bad coils? (will have to look that up)

thanks for any suggestions, least expensive ones first, please!

[MoVolvos]

-
Sounds like the front lower engine mount on the passenger side of the vehicle has collapsed?

https://www.matthewsvolvosite.com/forums ... =1&t=48430

Image at bottom of page
https://www.matthewsvolvosite.com/forums ... 9&start=14


Blessings,
BKM
-

[058ovlov]

You said you just replaced the plugs and the problem went away for 50 miles. So you were getting the same problem before you replaced the plugs right. In what way were the plugs bad. www.gnttype.org/techarea/engine/plugs.html And since it has reoccurred, have you pulled the new plugs out and checked those? That would probably tell a lot. Any other symptoms. e.g hard to start, smoke from exhaust etc..

[MoVolvos]

The car drives just fine when RPM are applied

That is the classic bad Engine Mount Symptom. It actually idles and drives fine (look at the rock steady RPM at idle) but the vibration, shuddering, sputtering is from the engine mount (teeth chattering) against the frame of the car. Pull the cover aside and inspect before proceeding with any other work. Your plugs probably required changing but the problem did not go away.

Blessings,
BKM
-

[sanfelice]

Thanks but..
I don't think it's the engine mount, as it's more like a misfire. Perhaps I was not clear in the original post. Again, only happens when hot, so I'm thinking that the plugs are getting fouled (need to check the new plugs but going away on vacation...) or the coils get hot and are not functioning, or... I don't know, maybe an idle control valve (is there one on these cars?)

thanks again.

[058ovlov]

@ BKM Yeah, you said that a couple of hours ago. Sorry if you feel you had to repost it, as if somehow, I questioning your expertise. All I was trying to do was get more info about his problem, to see if it might be something else.

I smell the unburned fuel after this occurs.

First thing that popped in my mind was the FPR. The reason that came to mind is that I once had the exact same symptoms, the only addition for me, was you had to crank the car twice after it sat, for it to start. And even though he makes no mention of RPMs' being erratic @ idle (Only to say the shuddering goes away when RPMs' are applied) My RPM's remained almost rock solid, even @ idle, while the car was still shuddering. None the less, one thing was unmistakeable. The smell of unburned gasoline. And while I will concede, that when any car shakes, but seems to even out when it is revved, may more than likely be the motor mounts. That is not always the case. And while it may very well be the OP problem. The ambiguous info he has given, hardly proves it so. (e.g. changed the plugs and the problem went away. albeit for only 50 miles) When I first bought my 850, a bad exhaust valve gave me the same symptoms as well. Only, that time it threw a CEL. These cars drive very smoothly even if they're just firing on 4 cylinders. Idling on 4. Well thats another story. Anyway, sorry to step on your toes. And to the OP. I would check the mounts as BKM has recommended. If by chance they are O.K., please try to explain your symptoms in more detail. e.g. how much does the car shudder, are there any other symptoms, what your previous and current plugs look like. etc..

Well I guess that answers that.

[sanfelice]

ooh, ooh! I also have to crank twice after it sits.
To reiterate, the shuddering seems much like a misfire, not a "vibration" or a knocking that may occur from an engine mount (although this is my first AWD, so the only other engine mounts I know are in my RWD cars). Still, I'll check the motor mount...

My guess is that the plugs are being fouled, but again, I'm guessing since the plugs I extracted were... well, awful! I'm actually surprised the car ran with those plugs. The RPM bounces around during the shuddering, but it is rock solid when cold. So...

[MoVolvos]

-
Hi 058ovlov,

With the limited info initially provided and our own feel and description of how a car behaves all of us can only make an educated guess by our experiences. The 50 miles could be just one or two trips and if the mount is borderline completely collapsed the new plugs may have made it run just smooth enough initially for the one or two trips. The description and symptoms warranted a look at the Mounts as it would be the simplest and quickest in terms of the process to eliminate from all other possibility as it can be way too many other things to look at before looking at the obvious.

You have not stepped on any toes at all and I hope I did not make you feel that you did.

Blessings,
BKM
-

[MoVolvos]

-

ooh, ooh! I also have to crank twice after it sits.

The RPM bounces around during the shuddering, but it is rock solid when cold. So...

Other possibilities.

00 VR as in V70? Is this similar to your rough idle?




Use as reference


Blessings,
BKM
-

[sanfelice]

the ETM fix was done by the PO so I'll assume (for the moment) that that is not the problem. Again, it is OK when cold. Rock solid. Needle doesn't move. Accelerates nicely. This only happens when hot, after a period of driving, sometimes 10 or more miles but the only reliable factor is that the car is hot when it occurs.