97 LeSabre lost drive on highway!!

[HYUAN7331]

Just bought 97 LeSabre limited, 109,000 miles. When drove on I-80 from Iowa City to Davenport, could reach 90 mph. However, in the middle of the way back, it suddenly lost speed around 70 mph. The speed quickly dropped below 50 mph. At same time, tach indication went crazy up to red zone with huge engine noise as I pressed the accelerator! I pulled off road and turned off the engine. After a while, I could start again and back on road at 65 mph. Unluckily, no more than 15 miles, the same thing happened again. I pulled out and back again. This time I kept the speed around 60 mph, no problem till I got home. What's wrong with it? Is it the transmission problem? Did GM recall 97 LeSabre for transmission problem before?

[public]

Check your vacuum modulator. It can cause all kinds of weird transmission problems. About $12 at most parts stores. You may also unplug the electrical connector on the EGR valve to test it. If the car performs fairly normal with it unplugged then you have found the issue. I had a similar issue with a 98 century. Turned out to be the EGR valve. I had no code and it was in the shop for a month after I gave up. The shop could not find the problem, I only found it through a lot of componient testing. Good Luck.

[HYUAN7331]

Thank you for your advice! I'm not an expert on car. So, where is the vacuum modulator located? Is EGR valve a part of it or a seperate thing? Is there any potential problem if unplug the connector? I mean, if the connector is useless, why would they use it?

[wallus]

No modulator on a '97. Is your trans fluid up? Is it brown and stinky?
If the fluid is full and still "pinkish" in color then maybe you should consider a trip to your local "tranny" shop for a computer diagnostics check.
It could save you some money in the long run.
On the other hand, if it has 109,000 on it you might want to change the fluid and filter.Filter may have collapsed (kind of glues itself together) or it could be plugged. Collapsed is bad, plugged is real bad!If the filter is bad and you've caught it on time this may solve your problem.
If it is plugged with debris from stuff that should still be in the trans, you may mask the problem for a while with a new filter, but it will come back someday.
A computer diagnostic test may show a solenoid problem which can be expensive to fix but it may shed some light on your problem before you "Dig in"

[buickmastermind]

Stinky=smells like burnt rubber. The only thing that could clog the filter is metal. Inspect your tranny fluid for miniscule metal flakes, easily seen under direct sunlight. I have never seen a filter collapse, but have heard of it happening. If it is a mechanical part breaking and grinding into the fluid, even changing the filter and fluid won't fix it, it will still have problems.

What it sounds like to me is that some of the seals and maybe a gasket is becoming warped with the heat and the high pressure of the fluid. The seal can't hold a high amount of pressure for long periods of time, and gives, causing an internal leak, and not being able to achieve the required pressure to keep the clutch engaged. Turning the car off disengages the fluid pump in the tranny, and the seal relaxes, and resets itself after a minute. It happens on the new trannys. The older ones had problems with valve springs collapsing, and eventual clutch stripping. If you want a quick fix, and don't want to bother with the problem for a while, use Lucas Transmission Treatment, the kind that helps fix seals and clutch plates tempararily. Eventually, you will have to rebuild it, but if you're lucky, not for a while.

[HYUAN7331]

Thank you for your advices! A computer test said the tranny slips! Help! What to do?

[buickmastermind]

Check the fluid for a burnt rubber smell, or metal flakes. Also note the color. It is likely time for a rebuild, fix the problem before it becomes worse. You can try the Lucas Transmission Treatment as I mentioned above, but that may or may not help.