Please help, car shuts off but restarts fine

[rv89]

Hello everyone,

I am new to the forum and have a 98 cobra. Recently it developed a wierd problem.


Car turns on fine and runs okay. As soon as it is warm and I begin to drive it, it will eventually shut off. Usually this happends when i am driving and slowing down. IT HOWEVER starts right up and keeps going until it shuts off again. Check fuses and all looks good. Please help.

Check engine turned on then shut off. battery is brand new.

Thanks

 

[mwolson]

Is your speedometer working?

 

[deadernie]

I'd check to see if you can pull any codes from the OBD since you had a check engine light. Had a fuel pump go out on my truck that showd the same symptoms. Would start & run for 10 to 15 minutes then die. But it would have to sit another 10 min to start again.

 

[PACIFICGREENSVT]

Aftermarket alarm?

 

[rich5150]

Hello everyone,

I am new to the forum and have a 98 cobra. Recently it developed a wierd problem.


Car turns on fine and runs okay. As soon as it is warm and I begin to drive it, it will eventually shut off. Usually this happends when i am driving and slowing down. IT HOWEVER starts right up and keeps going until it shuts off again. Check fuses and all looks good. Please help.

Check engine turned on then shut off. battery is brand new.

Thanks

Does the car idle/surge at idle at all?

As the car is sitting there idling, can you UNPLUG YOUR MAF sensor and does the car still run? If not, if the car dies, its probably your IAC.(intake air controller)

Usually when you unplug the MAF, the car will use something called the "failed Maf table" in the tune to allow the car to run.

If the IAC is dirty/not functioning correctly, it can't open up fast enough to allow enough air in the closed throttle situation(coming to a stop) thus your engine dies.

 

[rv89]

Is your speedometer working?

I think you are getting somwhere, speedometer does not work, jumps around

 

[rv89]

TTT, speedometer also stopped working properly

 

[mwolson]

When you let up on the throttle the PCM behaves differently if the car is moving than it does when it is stopped. It keeps the RPMs up a bit to keep the load from the power steering and power brakes from killing the engine. When you are stopped, that load is not there, so it drops the RPMs further, faster. In the tune, that function is called the dashpot function.

The Vehicle Speed Sensor (VSS) sends an electronic signal who's frequency increases with speed to the speedometer, but also to the PCM.

If the PCM does not see a working VSS signal, it assumes the car is not moving so it applies the dashpot function as if the car were not moving. But the RPMs drop too fast and the Brake/PS load kills the engine.

Fix your VSS and your problems will go away.