Engine/tranny surge when coming to a stop (2001 V70 XC)

[cruiserhead]

Car: 2001 V70 XC, 127K miles, USA spec.

Symptoms: When coming to a stop, the car surges ahead slightly just before or right at the stop ... engine revs a bit, and the car bucks forward an inch or two. Not in a dangerous-going-to-jump-into-the-intersection kind of way, but in a that's-really-annoying kind of way.

The transmission shifts smoothly through all gears during speed ups and slow downs. Except for the stop, if in fact this has something to do with shifting. There doesn't appear to be a difference in behavior when the car is cold or hot.

Transmission fluid is bright red, at the right level when measured hot, and there is no discoloration or burnt smell. I did a drain and refill of the transmission fluid about 6 months ago (after the above problem started appearing) using this method. Didn't notice a change in this problem.

Other possibly-interesting bits of info:

• A local Volvo mechanic identified a handful of broken/faulty mounts on the engine and transmission during a routine maintenance check on the car last year (but before I recall noticing this surging problem): right engine motor mount, lower transmission torque mount, upper engine torque arm bushing. Related?
• Seems to happen more often when coming to a gradual stop. Sudden stops don't seem to show the bad behavior.

I've read references to "B4 servo" and "software updates" related to this model year. I've owned the car since 2006, but do not know if either of these repairs have occurred on this car. I'm also rather clueless on what the problems are that suggest either of these as solutions.

Any ideas? Willing to get dirty and replace parts as needed. If the answer is "I need a new transmission," well, might be time for a new car.

[priapism]

Mine does that too. Does your idle go up and down? Ours does and I think it's related to that. You could try cleaning the MAF and throttle body, it might smooth the idle which could help the issue.

[Gunnar75]

My 2001 does that too, and I think mine is the dreaded ETM issue. No check engine light yet.

[EstVolvo]

I have the same question since mine is doing the same thing except engine revving. It has new mounts and new ETM.
Does your braking power increase significantly if you move the shifter from D to N just before coming to stop?
Just thinking out loud - could it be:
- Brake pedal is too late sending out message that it is time to disengage from gear?
- Solenoid(s) inside the transmission are sticking, leaking or worn?
- ABS module?
- ...

[z28chuck400hp]

have the same problem..as of this week...engine is "hunting" at idle and give a bit of a surge under braking sometimes..I got under the car and noticed the lover trans torque mount is bad and will change it....will let you know if it helps...also check engine light is on(wife did not mention that).. Can Auto Zone read code on Volvo? I think may be bad o2 sensor..

[wooded]

i have a 2001 with 205k and it does this, ive tried to track it down, cleaned maf, throttle body, plugs, injectors, fuel filter, new ignition coils,
i do not believe its tranny related as it still revs and slows if i take it put it in N and roll to a stop!
i read if you do this and your brakes feel squisshy( a technical term) then you may have a brake booster diaphragm issue causing a vacumn leak. i have not had this happen! I have no codes.
i'm trying the butane gas leak check( a small hose attached to unlit torch which affects idle) to track down vacumn leaks. best of luck to you all

[cruiserhead]

Posting an answer to my own question. It turns out that this was simply a failed electronic throttle module (ETM), a common failure on 2001 V70 models. The original unit had failed. After replacement, the problems have disappeared.

[wooded]

I apologize for my misleading statement about cleaning the etm before ( sprying while its running and seafoam treatment. I properly cleaned it by removing it and doing the soaking and cleaning with a fine wire brush when I removed the intake manifold for the pcv replacment procedure. it is not that tough to unbolt the 4 etm 10mm bolts, the tough part would be having enough length on the power cord. I had small blackenned areas. the change was absolutely dramatic, the surging went away completely and the idle is steady at 750! this was the most dramatic effect repair ive ever had. It was simply amazing.

[JRL]

Do not soak an ETM (probably ruined now)