Engine surges between 30 and 40 mph

[billr99]

Astro:

Hey, no offence taken. Just checking, as I figured you were questioning the dealer but I wanted to make sure I wasn't included in that lot.

BTW, on this subject I assume you have seen the Sonnax documentation on the AW 55-50 and 51 trannies? Pretty interesting stuff. If not, check out the documents available here (http://www.sonnax.com/technical-library/transmission). They do address specific Volvo differences, probably more than other OEM versions in fact. In one of these pieces it specifically addresses the in-and-out lockup issue. Of further interest, that documentation points to the SLU solenoid but it also states that 2-1 downshifts also aren't quite right when the SLU is need of adjustment. If I read it right, it also does not allude to any real pressure measurement to sort it via adjustment. Just says if you have this problem then just tweak the screw a turn. Kind of seat-of-the-pants but...

So can we assume that if you are having in-and-out lockup but not the other issues stated that we could be back to just plain bad programming which is what I still contend the basic problem is here? I love how getting any info on this stuff is like breaking the DaVinci code or something. Damn, to have my manual back....

Cheers,

Bill

[RJC409]

All,
Great bits of information and discussion. I'm getting stoked that I may actually get this problem solved without spending to awfully much more on this car. hopefully I can get to this before causing more damage to the trans. It seems to be getting more pronounced and not as subtle as when we first got the car. I hope these aren't signs that it is causing more damage.
I checked my trans fluid a couple of days ago and it is a medium brown olor and had quite a bit of metalic material on the dip stick as well. I think I will definitely begin with the flushing. I don't have a garage and will have to do the repairs in the driveway. We just got ~8 inches of snow so I may be waiting until it warms up a bit before I can get to the repairs on the valve body.

One other thing to look into. I've been discussing the same issue on another forum and one guy suggested that it could be plugged crankcase breather or vacuum leak. Says:

[I]"Crankcase breather or its vacuum line makes sense to me. Since your 'surging' is during low throttle(cruising low speed) there is actually vacuum in the intake. When boost starts coming online, negative pressure is gone and mode switches. A vacuum hose leak mascarades as coming on of boost so transmission disengages the torque lockup. Toggling between lock and unlock is felt as surging.[/I]If you fix the vacuum leak, a steady pressure/vacuum signal is feedback so no toggling of the torque lock up.

Says he has had to address this 100s of times.

Thoughts?

[RJC409]

It's the easiest way to go, made my transmission work a lot smoother after I bought the car with 120K mi on it. I changed the fluid several times before it got better, so you might not get instant results. I also installed an inline Magnefine filter and used TransTune to flush the gunk out of the solenoids and get them working smoothly again.

Is it best to run with the "TransTune" in the trans for a while before flushing?

[rkestner]

Same problem and symptoms-'surges' 3-4 on throttle, but doesn't in cruise or in manual. Volvo even sent a regional tech to look at our car some three years ago, and between him and the dealer, they kept the car for 2 days. In the end, the 'diagnosis' was a torque convertor problem to be solved by a transmission replacement with NO guarantee it would solve the problem. Guess what we did. We are still driving it as is with no change whatsoever. Prior to this diagnostic effort, we had the transmission flushed, updated software, reprogrammed the driving characteristics, etc. , etc.

Periodically I go through the forums here looking for a definitive diagnosis and solution. Unfortunately, none yet? Torque converter in and out without knowing why it does that. I continue to believe it is something in the electronics since it is okay in cruise and in manual.

[Brown Dog]

New pieces to the puzzle:

Surging occurs only when vehicle transmission is in auto mode. The surging stops if I shift from auto to manual mode while the surging is occuring. When shifted back to auto the it immediately begins to surge again.

This is exactly what my car has been doing lately, I also noticed along with shifting into manual mode that if you set cruise control it will stop surging and hold a steady RPM. I find its hard to drive this car the speed limit because it surges at 35 and 40 so much. Annoying as heck!

[Astro14]

Annoying but inherent in the programming - both my P2 cars do it...and they operate flawlessly in every other respect...I bump it into manual mode personally...but on my daily drive it doesn't usually happen...for me, it's pretty rare...

[RJC409]

The car has been sitting for the past few monthes until I could get to the bottom of the issue and put together the $ I needed to fix the problem.

Shortly after discussing the surging issue we started experiencing the shift flares and decided to park the car untill we could address the issue

I decided to go for the linear siolenoid replacement using the Rostra kit and a fluid flush.

All went very well and no more surging or shift flares. The transmission has been shifting perfectly for the past couple of weeks.

I now have a new problem. I don't think it is related but it sprang up so close to the siolenoid replacement that I am concerned that there is a relationship, hopefully just coincidental.

I was driving home a few days ago and pressed the accelerator to pass a couple cars. the trans shifted into passing range and the car accelerated aggressively and passed the cars just fine. As I was was finishing the acceleration the car acted strange with what seemed to be a shift flare (shifting out of passing) and then I started getting a louder exhaust/engine reving sound. I tried again to acclerate and the car would no longer downshift and the acceleration was very sluggish (much less power than normal). The car was doing fine with normal driving all the way home shifting normally. Every time I tried to accelerate it just boggs down with the lowder engine reving sound and slowly climbs in speed.

I would describe the "louder reving sound" as sounding like the engine is laboring or that there is and exhaust leek or bypass the opens up at that time.

Later that day, after the car had cooled, I started it to drive to the market and it died as soon as I got to the corner. I had to restart it 5-6 times, each time it sarted and as soon as I put it in drive and press on the pedal it sputters and dies or just dies. I finally got it back home by barely giving it any throttle and creeping up to a speed that I could get it home. once moving it seems okay and again seems to shift normal.

I don't know why but my gut make me think it is turbo related. If the turbo was shot could it cause this problem and keep the tarns from down shifting under acceleration, because it is getting incorrect feedback? Could it affect the cold running condition and explain why the car ran fine while I was driving it hot and poorly when I was driving it cold?

Any thoughts on what it could be this time?

[Astro14]

It's not a transmission problem, you should start a new thread.

I am struggling to completely understand your post...there is no "passing" range in a modern transmission, vernacular that used to refer to second gear in a three speed automatic, circa 1970...the trans simply downshifts to a lower gear, any one of several depending on speed...

From your description: after revving the engine to pass, it now makes more noise and stalls when given gas.

First thing I would do: open the hood, check the turbo piping over the engine and from the intercooler to the throttle body. Sounds like one of the hoses/pipes came loose, likely under pressure...

[jda2000]

Did you reset the fluid counter, reset the tranny adaptives and put the car in adaptive mode after the linear solenoids replacement?

If not, then it should be done to let the TCM adjust to the "new" tranny.

[RJC409]

It's not a transmission problem, you should start a new thread.

I am struggling to completely understand your post...there is no "passing" range in a modern transmission, vernacular that used to refer to second gear in a three speed automatic, circa 1970...the trans simply downshifts to a lower gear, any one of several depending on speed...

From your description: after revving the engine to pass, it now makes more noise and stalls when given gas.

First thing I would do: open the hood, check the turbo piping over the engine and from the intercooler to the throttle body. Sounds like one of the hoses/pipes came loose, likely under pressure...

Sounds like you got the point in my post just fine. Whatever you want to call it, when you press the throttle and the vehicle shifts into a lower range (gear). It's a lower range (gear) for "passing", call it whatever you want.

It doesn't just make more noise when given gas, it now does not shift into the "lower gear" either, it just boggs down.

Also, when I rev the engine, parked, it will only rev to about 3500rpm and then start to surge. when I let off the accelerator pedal it goes back to an idle but if I try to rev it again it dies.

Should I start a new post on this? As I investigate it more it doesn't seem to be related to the original problem.

I've checked the hoses and nothing obvious has come lose, but that is what it seems like. When the original incident occured, that was my impression, that something popped open/lose, but I cannot find anything obvious.