Hello, I have a 1998 Toyota Camry 4 cylinder automatic transmission. For the past couple of years, it has had trouble shifting into first or second when first starting out in cold weather. Also, the speedometer doesn't work until car warms up. This wasn't so bad, until it started thumping (I don't know how else to describe it) when stopped at lights, like it couldn't decide which gear to stay in. I had it plugged-in to a diagnostic tool and a trouble code for the vehicle speed sensor or ECM showed up. I then proceeded to buy a used vehicle speed sensor on ebay and after installing it, the car seemed to be ok for the first hour or so (it didn't knock or thump). However, later that day I started noticing that it was still doing so. From the beginning of the problem it would only knock once or twice at each light, but this soon got worse. The next cold morning, I tried driving it when cold, and the same speedometer/shifting problem was still there. Now the car is not only having the same cold issue, but every time the car is stopped, accelerating after slowing down, or from a stopped position, the car thumps over and over again (sporadically, not with even timing). It also struggles to accelerate from a stopped position now, but I don't think it's a fuel problem, especially with the other symptoms, but I don't know for sure. Right now I am considering buying a new engine control module, but I want to find out if that could be the issue before I spend the $$. Does anyone have any input? Thanks!

 

If the check engine light is still on, suggest you get the codes read and get the exact number(s) of the codes.

Is the overdrive light on?

Can you describe the thumping noise in more detail plus the approximate location?

Does the noise occur when trans is in neutral, reverse, drive, all gears?

Does the car have a RPM gauge, if so when the car is slow to accelerate does the RPM raise high but the car still move slowly?

Is the engine running OK, not missing, etc?

It might be the trans torque converter that is located behind the engine in the large housing that bolts to the engine. The trans is behind the torque converter.

Did the speedometer work OK when you replaced the speed sensor? If so, is it working OK now?

If the car is slow to accelerate it might a torque converter problem.

The speedo sensor also helps the computer to know when to shift. But this should not effect acceleration.

 

The check engine light usually only stays on when the weather is cold, and since we are having a warm spell, the initial shifting into first or second issue, the speedometer problem and the check engine light are not showing any problems. However, the thumping (which causes the engine to visibly shift) continues repeatedly in whatever gear the car is in. The only time it is not noticeable is when cruising at highway speed.

The trouble code that pulls up when the light is on, is P0500.

When accelerating, the transmission does not rev, and the tac doesn't show any dramatic change.

The engine seems to run great. I don't exactly know how to describe the sound. It is not very loud, more like an electrical short, causing it to make a sound similar to the normal sound it makes when changing from park to drive, or reverse.

The speedometer works fine as long as the weather is warm. When the weather gets cold, the speedometer will not work for the first few minutes, until the car warms up.

I am wondering about the engine control module still, since that trouble code comes up, and I replaced the VSS. It could have gotten a bad VSS however, since I bought it used on ebay. Then again, I may be completely off.

Is there a sensor or relay that controls the tork converter, and what are the usual symptoms of tork converter problems?

Thanks again for the advice!

 

By the way, the first thing I tried was changing the tranny fluid and replacing the filter. There were no unusual metal shavings that showed up, only the little bit of really fine fuzz on the magnets, so I don't think it's a mechanical issue. There is no overdrive light on either.

 

Code 0500 is the speed sensor. In general if the speedo works OK, the speed sensor is OK.

Does the car make the sound in Neutral, Park or when not moving?

Would be strange for a bad engine control module to cause a noise problem. But always a first time.

Try making 90 and 180 degree turns at low speeds and determine if the noise gets worse or comes from one side of the car.

If you are up to it you can test the speed sensor.

Jack up one tire, place trans in neutral. Find the computer and connect volt meter between the Violet/White wire and ground. Turn ign swith and slowly turn tire. Voltage should alternate between 0 and 4.5-5.5 volts.

Computer is behind the glove box.

 

It does make the noise when not moving (in any gear, including neutral), but it's not so much a noise as it is a jerking feeling, like when you move the shifter from park to drive. I will test the speed sensor though.

 

Watch the engine as it is running. If is shakes it could be bad engine mounts. Feel the engine and trans with your hand to help narrow down the location. You can use a section of hose as a stethoscope.