Hey guys, another desperate new member here needing help. I have a 96 Cobra and when you hit a bump it shuts off. It will start back but the guages dont work for a few seconds and runs like poo-poo. Then all of a sudden they come back to life and all is well till I hit another bump. It dont have to be a hard bump 2-3mph over a speedbump or even little bumps in the road. So far it has started back every time but my lucks gonna run out sonner or later. As im laid off right now I dont really have a fortune to spend on someone chasing loose connections. Anybody have any ideas of what or where to check? Its got to be something loose but I have no idea what, the voltage guage was running somewhat lower than usual a couple of days before hand I did notice. Im a welder not a mechanic please HELP. Thanks
A bump kills it
- Thread starter GABlackSnake
- Start date
wmburns
SN Certified Technician
Today’s computer controlled cars are much more sensitive to electrical problems. The cars’ computer controlled systems can not work without a constant proper electrical supply. IMO, the fault isolation needs to look at possibilities such as:
• Excessive load on the alternator/charging system.
• Weak or defective alternator.
• Bad battery
• Loose wiring to critical sensor/ECU or bad sensor.
• Wire chafing causing shorts.
• Bad grounds.
Since your post mentions that it happens when ever you go over a bump, you should concentrate on any loose wiring anywhere in the car. Pay close attention to the battery cables. This may be over looked because most people do not realize that the battery is REQUIRED to maintain the alternator field coil. The days of jumping a car with a totally dead battery are over. The bigger the alternator, the more important it is to have a good battery.
This could also be your battery itself. Consider that there is a weak grid plate inside the battery (or think low electrolyte sloshing around). Going over a bump causes a momentary interruption which causes the alternator to quit.
Check the connection inside the main power distribution module. Look for corroded or loose connections. Clean, clean, clean any those do not look perfect.
Your post did not mention what kind of sound system your ride has. Without any other information to go on, let’s assume that you have a big power stereo. If so, it is possible that a large electrical load is causing the alternator to be overloaded (collapsing field coil). Voltage drops, ECU looses its mind, car runs like crap. When the load decreases, the alternator recovers and eventually the car runs normally.
Your post did not mention any blown fuses. IMO, we can rule out shorts to ground. However, the possibility of a weak ground can not be ruled out. There are a lot of ground points on a car. Checking them all can be a huge job. IMO, you should start with any recent work done to the car.
An alternative is to data log the ECU voltage PID while going over a bump. If you see the voltage drop, this could help confirm that indeed this is a basic power problem instead of a sensor problem. If you do not have access to a scanner, connect a volt/ohm meter and have a buddy watch it while driving over a bump.
This kind of problem can be very difficult to track down. Start with the easy obvious stuff and work your way up. Unfortunately, the post doesn’t offer enough information to help beyond the general recommendations given.
Good luck.
• Excessive load on the alternator/charging system.
• Weak or defective alternator.
• Bad battery
• Loose wiring to critical sensor/ECU or bad sensor.
• Wire chafing causing shorts.
• Bad grounds.
Since your post mentions that it happens when ever you go over a bump, you should concentrate on any loose wiring anywhere in the car. Pay close attention to the battery cables. This may be over looked because most people do not realize that the battery is REQUIRED to maintain the alternator field coil. The days of jumping a car with a totally dead battery are over. The bigger the alternator, the more important it is to have a good battery.
This could also be your battery itself. Consider that there is a weak grid plate inside the battery (or think low electrolyte sloshing around). Going over a bump causes a momentary interruption which causes the alternator to quit.
Check the connection inside the main power distribution module. Look for corroded or loose connections. Clean, clean, clean any those do not look perfect.
Your post did not mention what kind of sound system your ride has. Without any other information to go on, let’s assume that you have a big power stereo. If so, it is possible that a large electrical load is causing the alternator to be overloaded (collapsing field coil). Voltage drops, ECU looses its mind, car runs like crap. When the load decreases, the alternator recovers and eventually the car runs normally.
Your post did not mention any blown fuses. IMO, we can rule out shorts to ground. However, the possibility of a weak ground can not be ruled out. There are a lot of ground points on a car. Checking them all can be a huge job. IMO, you should start with any recent work done to the car.
An alternative is to data log the ECU voltage PID while going over a bump. If you see the voltage drop, this could help confirm that indeed this is a basic power problem instead of a sensor problem. If you do not have access to a scanner, connect a volt/ohm meter and have a buddy watch it while driving over a bump.
This kind of problem can be very difficult to track down. Start with the easy obvious stuff and work your way up. Unfortunately, the post doesn’t offer enough information to help beyond the general recommendations given.
Good luck.
wmburns
SN Certified Technician
another idea
Were you able to fix your problem?
I just read an interesting post from a Crown Vic user. The posted stated that his car would shut off sometimes when going over a bump. The poster was able to track the problem down to a loose bolt connecting the battery cable to the Battery Junction Box (BJB). It seams that the bolt had worked it way loose and was making a weak connection.
However, it is still a good idea to keep your battery terminals clean. One less thing to bite you.
Were you able to fix your problem?
I just read an interesting post from a Crown Vic user. The posted stated that his car would shut off sometimes when going over a bump. The poster was able to track the problem down to a loose bolt connecting the battery cable to the Battery Junction Box (BJB). It seams that the bolt had worked it way loose and was making a weak connection.
However, it is still a good idea to keep your battery terminals clean. One less thing to bite you.
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