Just found the site today seems cool...sorry I'm asking a question right off but I'm lost...95 Bonneville...while driving around 75mph today the car shuttered and the check engine light came on. Car continued to hesitate till I got to my buddies shop. I shut it off. After a few minutes I started it up. No check engine light and ran fine. Ran a scan came up with...631...EST not toggling...What the hell does this mean...Please help...Thanks guy'*....Matt

I can't find any specifics on this but 631 EST is something with your ignition system. EST stands for Electronic Spark Timing (according to my '95 service manual). I would be looking in the direction of maybe you Ignition Control Module or maybe even a Knock
Sensor. Hope this helps some... :?

Could possibly be a crank sensor, too.

I goofed the code was 361 EST not toggling...not...631. It happened a few months back also. I thought it may be the cam/crank sensor. I just cant find the info on the code anywhere. Thank'* for the input...Matt

This error (361) sounded familiar. I went back and checked a problem I had just a few weeks ago. Checkout this link for more info.

http://www.friedpoodle.com/ba/forum/viewtopic.php?t=428

Cam sensor is out. That'* the reference for fuel injector firing. Ignition firing would have to be the crank sensor. From that link, I think it'* pretty well confirmed. I talked someone through this not too long ago. A couple others here could too. Probably about a 6 hour job for someone fairly familiar with cars.

It seems that that guy'* problem was the cam sensor...How do I go about testing either of the sensor'*?
I bought the car used a couple of year'* back and have 1yr/12k left on the warranty...don't know if it'* covered or not...

If this is an ignition problem, you're looking at the crank sensor.

If it'* a fuel delivery problem, you're talking about the cam sensor. By the error code you listed, I'm betting you have a crank sensor problem, Just like Gord.

We better nail this down before you did too far in the wrong direction!