Hello everyone,

I have a 1992 Volvo 960 wagon that I bought a couple years ago on the cheap as my first car. It had many problems, most of which were simple to fix. I learned a lot about cars from the experience. Everything has been sorted out except for one issue which has proved to be very elusive. I have been working on this issue for months, so bear with me as I describe my progress so far.

Let me start by listing the symptoms. The first thing I noticed on the first drive is that the car would shudder horribly to a stop when stopping from high gear, as if it was failing to downshift. The guy sold me the car really cheap because he thought the transmission was failing, but I have never ever seen it slip, so I figured it was something else. After some research, I initially thought that the torque converter lock-up solenoid was dead.

The second thing I noticed is that the climate control would (seemingly randomly) switch between the upper defrost vent and the face and bottom vents. After some investigation, I realized that it always worked as it should at idle, but never worked while climbing hills.

The last thing that I noticed is that the car would be very weak climbing hills until you pressed the pedal 2 entire inches further, at which point it would roar to life and the RPM would go to 4000. This also happens to a lesser extent on flat roads, making precise speed control very difficult. During this time the climate control would go completely dead except for the blower.

I suspected early on that the climate control issues were a vacuum leak as I had read that this could be caused by a leak in the bellows that control the flaps in the ductwork. On a hunch I disconnected the climate control from the vacuum lines to see if it was causing any other issues. Lo and behold the car is (sort-of) climbing hills and stopping without shuddering!

So the issues all appear to be related to vacuum. However, the car still shudders when stopping quickly or from high speed, and climbing hills is still tricky. At this point, I suspect that I have a larger vacuum leak somewhere. But before I take it to a shop for a smoke test, can you tell me if my logic here makes sense? I've spent inordinate amounts of time reading forum threads on this issue (thanks volvoforums!) but I have yet to ask any volvo experts about this. I want to get this solved soon because the stoplight shudders have started to become more "grindy", and I'm worried that I'm beginning to damage my transmission.

Sorry about the long post (if you've read this far you are a saint). I hope that this can be fixed easily!

Here's a condensed version of the issues:

• Climate control flaps cut out when engine is under load
• Car shudders violently when stopping until it comes out of gear
• Engine lacks power when climbing hills and is unresponsive to increased throttle, but roars to life when the pedal is pressed significantly more
• Removing the climate control system from the vacuum lines noticeably helps the shudders and hill-climbing but the issues still persist.

Eagerly awaiting your guidance,
Javaguru

 

How many miles are on the car?

A few things here, all maybe very easy to take care.

How does the trans fluid look and how does it smell? If other than bright red, it is time for a flush, a flush meaning, replace all 12-13 quarts, but don't us those machines at the oil change places. My car will tell me by being slow to undo the torque convertor lock up and deacceleration. Change the fluid, by using the trans cooler lines to the radiator, replace all of the fluid. It makes it shift better and the lock up releases when it should.

There is a well know vacuum leak in the climate control system, it is the bellows that does the recirc/fresh air valving. To fix permanently one has to remove the dashboard. Not fun ever. Takes about 10-14 hours of labor for a $30.00 part. Most just use a golf tee and seal off the offending line and live with the limited choices on the climate control.

But before it comes to that, check under the hood for vacuum leaks, especially and of the rubber elbow that make turns or bends to the plastic lines. These do deteriorate on the under sides, oil turns them to mush and then then get eaten away on the under side, so they can look normal with out viewing the undersides. Also the little check valves by the fire wall where the line goes into the dash board, these valves can leak. They should only work one way.

As for the lack of down shifting on the trans, I think your model has an adjustment attached to gas pedal linkage that electrically kicks down the trans when the pedal is pushed to certain point.

Hope this helps.

DanR '94 964 387,000 miles (153,000 on the new engine)

 

There is also this "vacuum port complex" on the intake manifold where all the little hoses connect. It is on the rear side of the manifold and you can see it looking down on it from above. I read a story where someone replaced all his vacuum tubes, and still heard hissing from this area (using another hose as a listening tube) and his problem turned out to be the o ring between this vacuum manifold and the intake manifold body.

I notice that my cold/warm air mix door won't move unless i'm decellerating or at idle.

I think that you should check the transmission for fault codes. There are many fault codes that don't light the arrow. I think you can blink them out on the older builds.