Pontiac Repair: 1998 Bonneville stall, crank shaft position sensor, crank sensor

Question
I have a 98 Bonneville SE 3.8 not supercharged 116,000 on it. When I run the car , it runs smooth and fine until about 12-15 miles then it sputters and catches and sputters again and the runs smooth the rest of the way. It is always at 12- 15 miles the tach responds to the sputtering and rpms surge and drop but the car does not die. No check engine light, new fuel pump and filter, new spark plugs (good ones), good wires. Any ideas?

Answer
Hi Steve:

the fact that the Tach jumps around as the engine is spitting and sputtering is a clue that it's an Ignition system fault. It could be a bad ignition module or a crank shaft position sensor one or the other. Ther is really no way to test either untill the car just outright stops running. Intermittant issues like this are heard to find! The fact that you have to drive it a while before it acts up is another clur to an electrical component driving that didtance puts enough heat into the bad component and makes it act up.. I would first off make sure you have good and clean and tight connections at the battery and at the ground wires on the engine. There is one under the ignition module and one behind the power steering pump on the block. If those are clean and tight My gues would lean more towards the crank sensor more so than the ignition module but Murphy's law it may not be that.. Good luck :)