Pontiac Repair: 2003 pontiac grand am gt 3.4l, wierd things, engine sensors

Question
2003 pontiac grand am gt 3.4l replaced ignition lock cylinder 6 months ago due to unable to turn key. last three months intermittent start problems when cold or damp. car will (a) turn over endlessly and not start or (b) starter will engage and disengage intermittently while holding key in start position. also note sometimes starter remains engaged temporarily periodically upon key release. couple of times car has stalled during warm up drive but restarted immediately. use of block heater almost always cures the problem. new fuel/air filters & plugs. wires good. is it possible ignition switch was damaged during replacement I have no trouble with anti-theft light. or possible fuel pump or ignition module trouble. I have also heard of wiring problems in dash.

Answer
Hi Craig.

I think your on the right track. I have seen ignition switches on thses cars cause all kinds of wierd things. One thing of note though when you turn the key to crank you are not actually commandin the engine to start through the switch. the switch sends a signal to the engine computer and then the computer controls the cranking of the engine. What happens is the contacts in the switch get burnt and created high resistance in the power feeds. Computer are VERY sensitive to loss of power and do all kinds of wierd stuff. The dampness addes to the resistance issue. what you can do is on a cold damp day checkto see when it will not start if you have fuel pressure and spark. if you have both of them it should start. If your missing one of thme you have to look into why. You may have a second issue with this with one of the engine sensors reading off a bit causing a hard start. The engine block heater has be puzzled it shoul have NO affect on the ignition switch which is making me think ther is another issue here somewhere. good luck :)