Erratic misfire (?)

SimLyons · Post by **SimLyons** » 03 Mar 2012, 22:30

We bought our V70R a year ago. I have been through the engine getting everything up to "like new". Fluids, plugs, detailed, etc. But the engine is giving out a very slight roughness, or semi-misfire at cruise. It accelerates fine, idles fine and seems great throughout the operating range except for this erratic "light misfire".

The plugs in the pic below are about 3K miles old. They are in order (one on left, 5 on right). They aren't perfectly clear, but even so it seems the plugs # 4 & 5 are running a little richer than the other 3. Gaps are right at .028.

So I replaced all the coil packs with "fresher" coils from my friendly auto recycler (low miles...about 32000). It now seems (in my mind) that it is a little smoother, but there is a new sound in the exhaust...kind of a "burble" with a missed beat now and then.

I'm going to take it out for a harder drive tomorrow (up the mountain) and see what happens. If anyone has experience like this from your S60R or V70R I'd sure like to hear if you fixed it. Or if that's just how it goes. Thanks!

eldims · Post by **eldims** » 04 Mar 2012, 03:22

Have you ruled out the transmission as the culprit. I imagine the misfire you described is a jerky feeling, which could as easily be coming from the transmission box. A quick check on the gearbox oil could be probably tell a lot.

Post by **JRL** » 04 Mar 2012, 06:46

C'mon, you know better than this, post the year and mileage.
Could be one of several frustrating P2R deals
Fuel rail sensor, BCV etc, but a steady speed miss is fairly rare occurence, usually these things happen under accelleration.
You will have stored codes so unless you go to the dealer to find the stored codes,or find someone who has VIDA DICE, you will be doing trial and error, pulling your hair out and wasting a heck of a lot of time here.
For under $200 you should consider buying a VIDA DICE set up so you can read internal codes and do other things with it that you can't do now

(BTW, installing "slightly" used parts is not the way to find a weird issue such as this. Either buy new or don't buy at all.
As mentioned, you need to get the stored code first to save yourself time and money)

SimLyons · Post by **SimLyons** » 04 Mar 2012, 12:05

For the curious, it's a 2006 V70R with 62K miles on it. It has exhibited this misfire since we bought it with 55K miles. The transmission was flushed completely 2000 miles ago. It's not a "jerky" miss. Rather, it is while level and cruising (with or without cruise engaged). Then it is more a feel than sound. Just a very slight seat-of-the-pants hesitation. I have no complaint about the fuel consumption. Not sure it's worth the $200 or so for the ability to get the codes. If they are in the engine controls they would show up on my CAN reader. Unless there is a deeper level of codes.

The #4 & 5 plugs do show more darkness (black) than the other three. But not enough to suggest there is no spark or overfueling....much. I'll see what happens on our drive up the mountain.

Post by **regent** » 04 Mar 2012, 12:21

Yes, there are Volvo proprietary codes that remain obscure to your reader. VIDA DiCe will pay for itself if you consider $95 + Tax for each visit to the 'stealership' to have the car talked to...

SimLyons · Post by **SimLyons** » 19 Mar 2012, 13:37

The latest update: Took the car in to the Volvo dealer last Friday. They did road test (short and quickly around the block). The computer found no codes at all! Arrrgh! They went in to reprogram the software in the trans and I already had the latest. The good news is that they charged me ZERO! I was stunned and slightly changed my opinion of tthis dealer.

The bad news is that nothing has changed. Still runs rough (slight) at cruise, virtually any speed (not under acceleration!). Any ideas anyone? Thanks!

RaymanSean · Post by **RaymanSean** » 21 Mar 2012, 07:08

You may no longer notice it, but even under cruise control your speed varies ever so slightly (a GM car seems to vary by as much as 3mph ~5km/h, or so I have noticed while driving several different manufacture's vehicles while following plenty of GM vehicles while they seem to speed up and slow down in a rhythmic fashion, my XC70 seems to do a much better job maintaining speed compared to GM) the same is true if you are using your foot to control your speed you are constantly making subtle adjustments due to changes in road conditions, wind speed, grade etc. I wonder if this hesitation is not the result of those subtle changes and perhaps a sticky throttle valve, waste gate, etc.

Another thought is that your ECU is getting an errant message from the transmission that the tranny is about to change gears, in modern cars to make the shifts as smooth as possible the ignition will be interrupted during the gear change.

Good luck

Post by **fazool** » 21 Mar 2012, 10:27

SimLyons wrote:The transmission was flushed completely 2000 miles ago.

Why ?

Post by **JRL** » 21 Mar 2012, 15:23

They ALL should be either flushed or drained and filled (depending on mileage) regularly,every 30-40K miles.

SimLyons · Post by **SimLyons** » 21 Mar 2012, 16:30

Agree with JRL. Regardless of the words in the owner's manual that it "never" needs changing, that is just marketing BS. Mine was somewhat thick and black! I did a complete flush and refill. It's now that nice "Jello-Red" color!

The "never" is based on someone's idea of the average miles the car is first owned. And on the driveline warranty. After that it is buyer-beware. (I worked in Marketing for a division of Volvo...Volvo Penta, for many years.)

It's pretty much common sense, too. It only costs a few bucks to change the fluid. It costs several thousand to replace the tranny.