Hello All,


I have a 1996 Saturn SC-2 with 156,000 miles on it that is having some mechanical issues. For two and a half years I have dealt with the engine occasionally stalling. It will fluctuate heavily before stalling, then simply dies. This does not set off any signal to the computer, so the Saturn dealership thinks I am crazy. They could not duplicate the problem, so they believe it does not exist. Itdoes not occur with extreme frequency, probably once every two weeks or so. After stalling out, you can put it in nuetral and it will start right back up, usually running without any issues for another week or so. Engaging the air conditioner makes the problem more frequent/almost unbearable. The engine runs rough with the a/c on and dies every time you come to a stop.


I have been told by an independant shop that this could be due to a faulty oxygen sensor, but the Saturn dealership has disagreed. I don't know how expensive replacing this sensor is, but if the mechanic at the dealership is "positive" that the sensor is not faulty, I cannot spend the money.


Any suggestions? I have a decent amount of mechanical aptitude, so I may be able to do some of this work on my own.


Thanks, Rufus

Based on mileage and behavior, sounds like it may be EGR valve related. If you've never had your EGR valve cleaned, you're overdue (assuming you burn as much oil as the rest of us).

If the egr valve pintle cannot move freely, it will cause the gyrations in rpm that you describe, usually on accel or decel (your case).

Running rough while the AC is on:

This is sort of consistent if you remember that the engine is under a steady increased load with the A/C on (akin to you leaning on the gas pedal just a bit...indefinitely). If the EGR pintle can't move freely, it probably can't make the small quick adjustments needed to even out the amount of exhaust gas being recirculated back to the intake needed to keep the engine running smoothly and idling smoothly when you decel and come to a stop.

You can remove the EGR valve and clean it and the ports on the engine where it mounts -- just be sure not to damage the gasket or you will need to get a new one -- you will likely find all kinds of carbon buildup.

There is an OUTSIDE chance that it is an issue with the TPS (Throttle Position Sensor), though this seems unlikely in your case since the problem is so intermittent. A TPS issue is usually a constant one, unless there is a particular portion of its range of motion which is giving inconsistent readings. A scan tool with real-time diags will allow you to quickly rule this out (or in).

Please post resolution

Derf

while you are at it it is probably time to change the coil packs and do a tune up if you have not done so recently

My last tune up was about a year and a half ago. I will work to clean up the EGR this weekend and if it improves performance, will post results.


Thanks for the suggestions!


Rufus