What is wrong with my car? The engine cuts off while driving sometimes, and it randomly will not start...

As far as the starting concern goes is the security light on solid or flashing when it doesnt start?Also when the car doesnt start or dies and wont start is the gas or temp gauge inop?Power door locks or keyless entry inop?Anything strange happening?Also have you had it scanned for codes yet?

Thanks for the reply. When the problem occurs, none of the lights are flashing. The last time the engine cut off, I took note of a few lights that were on (solid). These were the battery light, another that looks like an oil can, brake light (Because i turned on the parking brake), seatbelt light (I assume I took it off), and check oil light (mechanic forgets to reset). Nothing that seemed unusual. These lights may be on just because the key was in the "on" position. Gas and temp guage are working as normal. Tachometer and odometer at zero since the car is not moving. Power locks work fine. I don't use the keyless entry because my wife has the only one. I don't recall that ever having any issues either. Nothing particularly strange happening, except for the very first time it happened.

The first time it happened, it just wouldn't start. I methodically tried to narrow down the problem. Even though the battery seemed good, I tried to jump start from someone elses car. I didn't realize it, but the plastic covers on their battery terminals were swapped, and I didn't know that, and I burnt up the cables. Very embarassing. However, shortly after that, the car started up just fine. However, it was kinda shaky, and the transmission was shifting hard. A mechanic told me it might have gone into "limp mode" or something like that. The next time I drove, it was much better. There was a "check engine" light. I checked it at the auto part store and got 3 codes: P1780 (I believe the Park-Neutral Position switch) problem, P0300 (Random Multiple Engine Misfire detected), and P0727 - Engine Speed Input Circuit No Signal However, the check engine light has disappeared since then and never came on again since then. I have told some mechanics about these codes, but they didn't seem to think that they were relevant because the check engine light had gone off since then. I have heard that GM has a computer scanner that does a much more thorough job than the typical ODBII scanner. I haven't had one of those done yet. BTW, I appreciate your response, and I would love to get this fixed.

Alright do this for me take the car to the auto parts store and have them scan it for codes just to be sure there isnt any codes.If there is write the numbers down.Let me know what you find.Next your going to have to check for spark when it wont start.It sounds like a bad crank shaft sensor though.

Thanks again for the response. Today, my plan was to drive it for a few minutes and then turn it off at the mechanic garage. My hope is that it would not start, and they could try to diagnose the problem while present. However, before I could get there, the engine shut off completely while I was going about 35 mph. I parked on the side of the road. I took a short video with my phone, but this forum doesn't allow 3gp file format, so unfortunately I cannot post it for you. After this I walked home. After about 1-2 hours, I came back and it still wouldn't start. A friend and I pushed it for about 1/3 mile before taking a break. I tried turning the key. Surprise, surprise- it started again. However, this time, the check engine light was on and it was shifting hard (perhaps limp mode?). I drove it to the mechanic shop and left it with them to give another shot at diagnosing the problem. The last time that happened, I was given 3 codes: P1780, P0727, and P0300. I hope to hear back from them soon. I will let you know as soon as I find out what error codes it gives me.

BTW, from the beginning, my best assumption was that it was either a fuel pump or crankshaft position sensor (CPS). If it turns out to be the CPS, how hard would that be to replace?

There really easy to replace let me know what codes they find.

Hey again, I just got back from checking w/ the mechanic shop. The owner of the shop told me the mechanic read the code and thinks he knows what the problem is, and that they have the part in stock, but that he's not fully sure about it yet. He didn't say exactly what it was, but after I asked what the code revealed, he said that it indicated the crankshaft sensor. He said they want to drive it a bit before feeling confident that is the problem (because last time they replaced the fuel pump and it still wasn't fixed). The owner sounded as if he wanted to get this thing fixed for me as a courtesy since the last time they didn't fix it. I really hope that they do get it fixed. Unfortunately, I do not have the specific error code, but based upon what the owner told me, it seems that it indicated a problem with the crankshaft sensor. I will keep you updated as I find out more. If they ensure me that the CPS is the problem and the quoted estimate is higher than I think it should be, then do you think you could walk me through fixing it? Thanks!

If they replaced the fuel pump last time to fix this problem that was a terrible guess and should refund you the money for the fuel pump repair which would be much higher then replacing the crank shaft sensor replacement.Thenjust charge you for replacing the crank shaft sensor.Or better yet just replace the crank shaft sensor for free for all your trouble.If they charged me 500-600 or more to replace the fuel pump to fix thay problem and it was still happening i would be asking for a refund for the repair.And if they didnt give it to me i would be taking them to small claims court.Which should be a easy win since it clearly didnt fix the problem.Fuel pumps when they go bad dont have those symptoms when they fail they ususally dont restart later.I have seen very few do that like once in a blue moon.Most of the time they wont restart unless you smack the fuel tank and they dont always restart then ethier.So i would be talking to them about a refund for the fuel pump replacement.Unless you agreed that they could guess the fuel pump and if it didnt work then they wernt held liable?But i could help you to replace it its held inby one bolt and unplug a connector.I cant see give them anymore money at this point.I hope there not charging you more money for diagnoses?After they grossly miss diagnosed it as a fuel pump.

I would ask them how they diagnosed it as a bad fuel pump to begin with since when the crank shaft position sensor fails you lose spark not fuel pressure.Also when the crank sensor fails it doesnt always set a code for it.

Thanks for the response. Yeah, I wasn't too happy about all of it either. When they replaced the fuel pump, somebody else had paid for it to be repaired. When I brought the car back, they didn't charge anything to take another look at it. Today, when I came back to them, they told me that it was the crankshaft sensor and that they had replaced it for me. There was no charge. I don't know exactly how much the fuel pump cost, and though I'm sure it was more than the Crankshaft sensor, my main concern is that the car is now fixed. At least it's supposed to be fixed. I'll probably find out for sure about that within the next day or so. I'll let you know if it still gives me any more problems. Thanks for all the help. I really wasn't sure if the mechanic shop was going to "make it right" and actually fix my car or not. , but I really needed some help getting through all of this because I would have refused to give that shop any more money.

To replace the fuel pump in my area its 625-746.The crank shaft position sensor is 15 plus tax and about a 1hr labor max so they were more then happy to give you the crank shaft sensor for free.Rather then refund the fuel pump repair.Hopefully its fixed now i feel sorry for the person that paid for that fuel pump repair that didnt fix the problem.

By the way, thanks for all the help last year. The problem was cured by replacing the Crankshaft Position Sensor. I thought I would write that in case somebody else had the same problem.

I had a feeling it was the crank shaft sensor since you had a code P0727 I have seen bad sensors set those codes.Also your welcome that's what were here for.