XC70 shuddering problem

Esjay · Post by **Esjay** » 17 Apr 2021, 14:00

Hi everyone,
I am having a new problem with my 2006 XC70, 2.5T with 148K miles. Check engine light is not on and it is not showing any codes on my OBDII scanner. The problem only occurs at highway speeds. When I hit the accelerator to pass another car or to maintain my speed up a hill, the car kind of shudders and loses power until you take your foot off the accelerator. It happens only when the accelerator is engaged beyond a small degree. If the accelerator is depressed just slightly, it does not happen, and the car seems to accelerate just fine from a stop or from slower speeds. Any suggestions on where to look would be appreciated! Thanks.

Post by **jonesg** » 17 Apr 2021, 15:25

I would suspect a coil not firing under load.
Or motor mount.

ignatz · Post by **ignatz** » 17 Apr 2021, 15:39

My 2001 V70 2.4t just started doing the same thing today. I was at 50,000 miles on the plugs, so I changed them. One looked like it had a little piece missing from the insulator. I hope that was the problem. The other plugs looked like plugs with 50,000 miles.
I won't be able to report a definite fix until tomorrow evening. I'll be doing about 150 miles tomorrow, so that should be enough driving to tell.
Same thing.....passing a car on the turnpike and it starts stumbling at 75mph.....no check engine light too. I was hoping to get 60,000 miles out of the plugs, but will be happy if this fixes this.Will report back tomorrow.

Esjay · Post by **Esjay** » 17 Apr 2021, 17:57

I appreciate the replies...not sure how many miles the plugs have on them, it is probably worth getting some new ones anyway and checking out the coils while I'm at it. I'll also check out the motor mounts. Thanks.

ignatz · Post by **ignatz** » 18 Apr 2021, 03:04

To note, I had a set of Volvo plugs in my home parts inventory. That made initial plan of attack easier.

Post by **abscate** » 18 Apr 2021, 05:47

You might drive it carefully for a few hundred miles until it generates enough data to set a misfire code and point to a certain cylinder, but at 150k miles the pm approach would be 5 new Bosch coils

Since I run a lot of these cars I have three that I put new coils in at 100k and use the old ones in the 3 other run-to-fail cars

ignatz · Post by **ignatz** » 18 Apr 2021, 14:00

Just got back from my 150 mile trip. Plugs did the trick for me, but will probably think about new Bosch coils. I'm at 188,000 miles with original coils and want to keep racking up the miles.
I can zoom up to 80 without a flutter.

Esjay · Post by **Esjay** » 19 Apr 2021, 04:58

Thanks ignatz and abscate. What is weird to me is this: why does this happen only once I have attained a cruising speed of about 55-60 mph? If I am stopped, or just going slow, I can hit the accelerator hard and the car reacts normally. It takes off with full power and no hesitation. I would think that if a plug, or plugs, or a coil has gone bad, that this shuddering would happen all the time when I hit the gas pedal....Do you know of a good bench test for determining whether a coil is bad?

ignatz · Post by **ignatz** » 19 Apr 2021, 06:47

As my wife was with me two days ago in the car when it was shuddering, she then reminded me that it did this back in January. We hiked around Lehigh Gap and when leaving had to drive up a long steep hill. About half way up the hill at around 35-40 mph, it started shuttering. I backed out the throttle, made it up the hill and went home without a problem.
Because my car was going in for state inspection that week, I asked them to replace the fuel filter at that time. My car didn't have another symptom until two days ago.
Also, in a 70mph speed zone, I'm the Volvo driver doing 67mph. I'm not usually passing people, but two days ago I was going up a long grade passing someone.
In my case this weekend, my wagon was packed up for a Saturday and Sunday trip and I didn't want to move everything over to my 2002 V70. Because I had a set of plugs at home. I threw them in and the car worked. Because my 2001 V70 is my main driver, I should just replace the 20 year old coil packs and move on.
Another note about my 01 V70 2.4t.......it uses about a quart of oil every 1,200 miles or so. At 50,000 miles on the plugs they looked fine. Just wear on the electrodes, not showing signs of oil fouling. Iv'e never seen smoke come out of the exhaust pipe, doesn't leak a drop of oil. Also the PCV stuff was replaced and that didn't help the oil consumption. So, I was happy to see that the plugs were not showing signs of oil fouling.

Post by **jonesg** » 19 Apr 2021, 09:10

Esjay wrote: ↑19 Apr 2021, 04:58 Thanks ignatz and abscate. What is weird to me is this: why does this happen only once I have attained a cruising speed of about 55-60 mph? If I am stopped, or just going slow, I can hit the accelerator hard and the car reacts normally. It takes off with full power and no hesitation. I would think that if a plug, or plugs, or a coil has gone bad, that this shuddering would happen all the time when I hit the gas pedal....Do you know of a good bench test for determining whether a coil is bad?

At slow speed the coils are not running hot.