Scotty, How are you? This might be a stumper. I have a 2008 Pontiac Grand Prix. 3.8L V6 3800 series. New battery, radiator, waterpump and alternator. The body has 190k on it and a newer engine was installed with 89k on it. All was fine for about 6 months after the engine was put in so I feel confident that the issue resides somewhere else. What happens is when I hit a bump or turn to sharp, all of my electrical cuts out. I sometimes get an anti-theft system needs servicing come across the display but not all the time. The horn may or may not beep when it does this. IF the car does have the anti-theft(less often of this happening) thing come up I can rarely get above over 3k rpms and if I shut the car off I won't be able to start it for a while. But sometimes even if it doesn't the car won't start randomly. When I say it won't start I mean it acts like there is no power what so ever. Dome doesn't even come on with the door open. I have checked for loose grounds or cut wires. All this started around the same time my left rear signal went out after I replaced it. But not the same day, probably within the same week. Please help. This is the only car getting me back and forth and I can't afford a replacement. Thanks for taking a peek if you can and let me know if you need anymore info.
You may have some loose electrical connections. Check the battery terminal connections and make sure they are re rust free and tight. Also, find out where the ground wires are, remove them, clean them and put them back. GM has issues with grounding.
Can also check the key if checking the grounds do not work for you. I had the same problem when I had my pontiac. I was hella stumped too. Turned out my key was too old/worn. Was jiggling and causing the car to think it was being attacked haha. Got a new key and reprogrammed the new one. Boom, never had the problem again.
Definitely sounds like loose grounds somewhere. Pretty typical for those cars as they age.
So it has been a few days since I started the car waiting to hear some answers. I let it warm up in the usual fasion waiting for the rpms to come down. This problem is new but still the same issue. I put the car into drive and it just wanted to stall out on me. I'm going to try the key solution since the anti-theft is linked directly to the ignition and hopefully that's the issue. I did go through and check the grounds. There were 3(maybe). One under the fuse box in the engine bay, one under the engine that connects to the motor and I believe one under the car in the rear end. Also my tail light went out again. This litterally happened like 15 minutes ago from me posting this. I don't know where any other grounds are. I have a set of ramps and a jack but nothing like a lift to actually get up under it and check. Also I had a new catalytic converter put in it with new sensors so it's unlikely thats the issue although I have been told that vehicles with these types of computers tend to program themselves to how the driver uses the vehicle. Not sure if that's true or not but either way when I am able to drive it, I baby the hell out of it. The sun just popped out so I'm going to take advantage of it and see if I can't find a loose connection somewhere or another bad ground.
I'm rewiring all my grounds from the battery to frame/components. I'll let you guys know what happens.
That's the way to eliminate all those possibilities. Kudos for your patience and persistence.
the root cause is not necessarily an electric issue... could be very well a major vacuum leak that is triggered when the engine block shift on a bump or pothole or a turn... my son had similar problem with his 2003 Ford Taurus.. mechanic and dealer could not reproduce the issue... I ended up tracing the lines.. found the elbow rubber hose that connects the PCV to the intake was cracked on the inside. On a smooth road the crack was pretty shut that is wasn't sucking air. on rough road, or even stopping hard at a traffic light the engine block moved forcing the crack to open, suck enough air to trigger the system to shut off to protect the engine... the car start find afterward. A smoking machine would have detected the leak inside the elbow. wasted about $200 on diagnostics when I ultimately fixed the problem for $12.
