P2 2001 V70XC 'Stutter' driveability change with cruise on / cruise off

stevek924 · Post by **stevek924** » 20 Jun 2022, 19:35

My 01 v70XC (285K miles) developed an issue with the cruise control. Initially started about 4 months ago with what felt like a 'hard downshift' when going up a moderately steep incline with the cruise control on. A loud 'clunk', and the accompanying jerk felt in the cabin. Did this only occasionally, maybe 3 occurrences over a couple of months.
Now, with the cruise control engaged, it has progressed to an intermittent, fairly severe, 'stutter' like 3 of the 5 cylinders are misfiring. Get the drivetrain clunking and a lot of stuttering or shuddering. This current issue always happened at relatively low speed, 45/55 mph and low rpm 1500/2000 rpm. Today it happened at the lower speed, then one time at highway speed (70 mph), then again at lower speed all. All on the same trip, all when going up a slight incline.
Turning the cruise control off, or pausing it, clears the problem immediately. This only happens with cruise control on, no issues with the car at all with cruise off. And on relatively flat roads, or an incline steep enough to get a downshift, everything is fine with cruise on.
With the initial occasional 'hard downshift' I was thinking transmission or drivetrain. I'm now leaning toward a fuel problem, either fuel delivery or throttle body module. The throttle body module was replaced about 2 1/2 years / 30000 miles. ago. That was for a 'no start' problem.
I'm looking for insight from the group. Would like to do some troubleshooting before handing it over to a dealer.
Was going to start with checking fuel pressure. Coming up on 300K miles, was planning on doing coil packs and plugs. Wouldn't be a stretch to do fuel injectors too.
Anyone have any thoughts?

Post by **Blacklab467** » 20 Jun 2022, 20:19

Mine does weird things when the cruise control is used also! It throws a code that I cannot recall the number right now and goes into limp mode. I've had to pull over and clear the code with my OBD2 scanner to get home. I haven't looked very far into it, I just don't use the cruise control anymore. It usually happens when the cruise is on and it has to downshift because of a hill or headwind. I'd be curious as to what you find. I don't currently have time to work on this issue right now.

ignatz · Post by **ignatz** » 21 Jun 2022, 03:54

Try plugs first.

Post by **br0dy519** » 21 Jun 2022, 07:04

It sounds like you're on the right track with misfire. I had a similar issue on both of my cars. One of them was a vacuum leak and throttle body problem, the other was a misfire (bad coil). They both cruise fine now. Not a bad idea to hit regular maintenance items too... air filter/fuel filter.

stevek924 · Post by **stevek924** » 23 Jun 2022, 19:36

Thanks All. I'll post the fix (assuming there is one

Jerrycan · Post by **Jerrycan** » 01 Jul 2022, 03:23

I had this a couple of months ago and fitted a new boost pressure control valve and it's fixed. It was literally a 10 minute job and cost £43 GB Pounds. It is located under a plastic cover which is just clipped in place on the lefthand side of the engine bay (looking from inside the car) just behind the headlight. The valve has 3 rubber tubes and an electrical plug which need swapping over.

leapdragon · Post by **leapdragon** » 08 Aug 2022, 15:47

I purchased a 2007 XC70 about a year and a half ago (to replace my 2002, which replaced a 2000

) and I was having a very similar stutter on cruise or sometimes just by foot when at highway speeds, especially with inclines.

Based on a few helpful replies here, I put in new plugs, a full new coil set, and a new fuel pressure regulator. Stutter disappeared. I suspect the plugs/coils did the trick.

Post by **abscate** » 09 Aug 2022, 06:06

This is fascinating thread. The difference between cruise and non-cruise is that the ECU a request torque via the PWm signal from the gas pedal in non-cruise, but from a closed loop swerve based on vehicle speed with cruise on. Why driveability should vary is an interesting question.

But, as is often worth noting, Stage 0 is the starting point for troubleshooting.

Post by **Blacklab467** » 09 Aug 2022, 06:53

Could you expound on this, Abscate? My ‘03 xc does this exact shudder with the cruise on such that I stopped using it. The first time it happened I thought that the fuel pump was failing and the fuel supply was intermittent. It’s done it several times over the years, most recently going into limp mode and throwing a code I cannot remember. As I mentioned, I don’t have VIDA,
I think this is a common problem and it clearly has to do with the difference in communication protocol when the cruise control in in use. This one has stymied me for years also!

Post by **abscate** » 10 Aug 2022, 07:47

I have no insight here. There should not be an iota of difference in driveability with cruise on/off. When you put your foot down, the pedal sends a signal to the ECU for more torque. That opens the throttle body, and voila, more torque.

With cruise on, the ECU requests torque in response to changes in vehicle speed, much smaller than you can notice, but with exactly the same method - the throttle body.

...and that might be the answer.

In cruise, the bandwidth of the loop might be a lot higher as the ECU keeps speed constant to well within 1 mph. The pedal response can be 5-10x coarser. I wonder if the right combinations of stuff worn gives you the stutter because of the higher response bandwidth.