I have a 1995 Buick Regal GS 3.8 and the two codes that came up are TPS Sensor Circuit Lean and Knock Sensor - the car wants to cut out and when I put the turn signal on the needles jump around - how do I know which one I should change?

I've contacted the resident Buick Regal Expert, llregal, hopefully will emerge from his casket and answer you...personally have no particular knowledge, but would be willing to research this for you, but let's wait for the Buick Regal expert to make his appearance here, he's been notified, now.

H25 is a good man and equally experienced at this...we will just wait...

Awesome guys I am spending alot of money to make this thing run - gave her a tune up and things started happening - unfortunately this is my bread and butter and i drive a lot of kids around - starting to get dangerous!

if you haven't changed your battery in five years, now's the time...when you do, make sure the connection from frame to battery is sound and can pull 300 amps and the connection to the motor can pull 300 amps CCA too- when you have good steady fresh ground for power the sensors will be operating with clean power and we will no longer have 'brown' power failures~

This is the second one today that has jumping needles with rear lights on. I don't think it has anything to do with a engine control system. That seems like the power to the gauges is fluctuating for some reason. --- When it comes down to a TPS or a Knock sensor, I don't know if one is more viable. They both may be good and the root cause of the problem is tied into the power fluctuation somehow. It's less likely that both systems failed at the same time.

That Airtex proximity sensor should be used for the gas gauges. There's been a lot of failures with the wire wound variable resisters. Airtex Engineering Tour with EricTheCarGuy video -- http://www.youtube.com/watch? v=lMVvuME22M0&list=PLC3D53EBD790DDA9C&index=9