94 Grand Am Engine Trouble

My daughter has a 1994 Grand Am with the V-6 engine. She has a problem in that occasionally when going uphill at 65-70 mph the engine will start to run rough. At first we will feel a small amount of shaking in the engine and it quickly progresses to the point the engine feels like it is going to shake apart. If it is given more gas or less the problem will stop. It does not happen all the time and is hard to induce. I thought it might be a suspension problem when first described but have eliminated that possibilty. Any help would be greatly appreciated! John.

my daughter's 94 Grand Am (128K miles) has a very similar problem. We had the wires changed and the injectors cleaned, which improved it somewhat, but at between 60 and 65 mph, it still jerks once or twice when going up a moderate incline. I'm wondering if it could be something to do with the EGR system.?????

Just an update of my original post. I had to put a new thermostat in the car and while I had the upper intake off I checked the EGR valve passage and found it completely blocked with carbon. Worked on it a couple of hours and got it cleared out. No more "Check Engine Light". Changed plugs and wires and car purrs like a kitten now. Hope this may help someone else. John.