Oldsmobile/Buick Repair: my 97 buick lesabre, port fuel injection, throttle position sensor

Question
I have a 97 Buick Lesabre with 119,000 miles on it. Never had any problems with it before until the other day when I was driving to work, I noticed my car was shaking a little and shifting funny when I was doing about 30-35 miles an hour. When I drove it home when I got off of work I noticed my engine light on and when my car would hit 30 miles an hour it would start shaking really bad until I took my foot off of the gas. My car is idiling fine and no other problems that I notice until I hit 30 mph. Can this have something to do with my trans? If you can email me back and give my a heads up and your advice I would highly appreciate it. Thanks and have a good day.

Dwight A. Patrick

Answer
Hello Dwight,
Here are some links that might help.

There are a few things that could cause it.
Low fuel pressure due to a dirty fuel filter, a bad fuel pump, or a ruptured hose inside the fuel tank, from the pump, could cause it. I would test the pressure, but then, I have a pressure tester, and it is easy for me. A new filter as a guess might do it, and for sure wouldn't hurt anything.
It needs to have a full 13-PSI while the engine is running if it has throttle body injection. Yours I believe will have Central Port Fuel Injection of one kind or another, and will probably need about 45 PSI.

Another thing that could cause it is a bad throttle position sensor, which can be tested with a scan tool, or an ohmmeter.

A dirty mass airflow sensor could also cause it, but again, please don't just go buy this stuff on a guess. It can be tested, as well as cleaned. See this link for an explanation of how it works, as well as how to clean one. It is a FORD link, but they work just the same.
http://www.fordscorpio.co.uk/cleanmaf.htm

Then there is the temperature sensor. Read the comments in the following link, from a forum I spend a lot of time at. You will probably want to sign in and spend some time there yourself. It is FREE, and a lot of good information.

http://www.chevytalk.org/threads/showthreaded.php?Cat=0&Number=1366279

Lastly, I have a Cutlass, and it shuddered as it shifted into Overdrive. I mean it shook like crazy till you let up on the throttle, or floored it. My problem turned out to be a broken valve spring on one cylinder.

Good luck,

Van