Dear Tom & Ray,
I have a bewildering problem with my 2003 Pontiac Grand Prix SE with a 3.1L Motor with 130k miles. One day after sitting for an hour, the car wouldn’t start. It would turn over, but didn’t start. After a few minutes, it started and ran fine. I had this happen to me on a previous GM car and a new fuel pump solved the problem. So $300 and 3 hours later, I thought I had it fixed. Not so. When driving, the car just died. After about 15 minutes later, it started, ran perfectly, and I went home. It did this again a few days later, so when it started I drove it to my mechanic and dropped it off. My mechanic has been very competent and reasonable in the past. BTW, the car is NOT saving any codes… the dummy light isn’t coming on. After having the car for two days, my mechanic could not pin-point the problem and, of course, could not re-create the problem either. After much research, he decided the only thing it could be is the ignition module (the thing the coils plug in to). He sold me the part, did not charge me for his time (but marked up the part I’m sure, but I have no problem with that). So I changed that, and a week later, the problem happened again. But this time, I noticed it was going to happen, so I floored the accelerator, hoping that if I kept fuel being drawn into the engine, it might re-fire. Well the engine sputtered, and sputtered, barely firing at all. Then about 10 seconds later, it fired up and ran perfectly all the way home. Again, no codes. 20k miles ago I changed the fuel filter, plugs, plug wires, and cleaned the fuel injectors. 6 months ago i spent $3k on a new transmission, axles, oil pan gasket, and a wheel bearing. Therefore, i’m not quite ready to get rid of the car. I am completely stumped, and so is my mechanic. Do you have any ideas? BTW, love the show!
Dear Tom & Ray,
A faulty crankshaft position sensor can cause this problem. The problem is, the sensor has to be in the failure mode to determine if it’s the cause.
The trouble could very well be the CPS sensor as Tester suggested. There could also be a faulty power connection to the ignition system. When a car doesn’t start up like it should the ignition system is a sure suspect.
The other description you give about the engine sputtering while on the road does indeed sound like a fuel system problem. Perhaps the fuel pressure regulator has a problem. You may want to carry a can of starting fluid with you to have on hand when the trouble happens again. If spraying some fluid into the intake doesn’t make a difference then the trouble would have to be with the ignition system in my opinion.
Thank you for the input. I’m ruling out a fuel system problem because the last time the car left me stranded, I had my timing light with me. I hooked it up, and while turning the car over, I hit the timing light and got nothing. It was only when the car started and ran when the timing light worked again. Does that make sense? I’ll definitely keep a can of starter fluid in the car to try that. Without having all of the proper testing equipment is it worth it to throw the CPS at it to see if that fixes the problem? How would I test the CPS by “putting” it in failure mode? At this point I’m getting a little out of my element… a shade tree mechanic I am, but not a very sophisticated one!
Since it now looks to be an ignition problem you could install a small light to the power lead of the ignition system so you could verify power is getting to it when the trouble happens.
You could replace the CPS sensor in an effort to prevent another break down. It might help but until it is proven bad it is taking a guess and it may not help. Those sensors can be intermittent so replacing it may be what is needed.