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car ia shutting down and tach is shutting off when i drive sometimes

R

ronpsr1950

New member
My 2000 Pontiac Grand Prix has the following problems. I will be driving and the tachometer will drop to zero and the car will jerk but still run. Now I am also having problems with the car shutting off but it usually restarts and the tach will work after restarting too. It seems to be a worse problem when its extremely hot. Sometime the car won't start and sometimes it will run but shut down and the exhaust stinks like it is real lean. The other day it would not start and i checked it had no spark so I changed the control module and it seemed to be okay for a couple of weeks. Now it is doing it again. Does anyone have ideas or had the same problem? Would a crank sensor cause this? And what symptoms would a bad cam sensor give me. There are no codes being thrown off by the computer. Any ideas or help would be appreciated
 


Agreed with the others. The tach gets its signal from the crank sensor. If there is an interruption in this signal even for a split sec, the tach will drop to 0 and not work again till you shut the car off and restart it. That's how I figured out my intermittent starting problems were the CPS on mine. Eventually, it started doing just like yours, where I'd feel the car shutter like someone just bumped the car from behind, and then the tack would go to 0 even though the car was still running.
 


My 98 had a problem similar to yours started a month after i bought it. I thought i was screwed and bought a piece of junk. (I did, but its because of rust)
Mine wold seem like it was missing a beat, act like it would die rpms go to zero but then keep running but the tach would stay at zero. So I took it to a mechanic friend with a giant snap on tool box and a $hit load of tool$ and the latest computer junk lol. He could not find any thing wrong and i could not make it happen on almost an hour test drive with him. He said "it sounds like the crank sensors about to go" paid him to do the crank sensor $130. Well went to get it and on the way home it did it. lol I was determined to find it. I knew that the car had thrown a belt at some point. (underside hood insulator will be ripped) From past experience with belt tossing, it can mess up wires if they are whipped by belt pieces.

Looking at the Front of the engine locate the coil pack set up there is a plug at the bottom. Inspect the wires for breaks and the plug for any corrosion. I found a wire that was broken and one that was stripped of insulation. I fixed those wires and cleaned the plug and the ignition modal plug popped the coils off and cleaned all those connections. I have not had the problem since.
Just a suggestion not a diagnosis. Have a good look and use a good flashlight. good luck!
 
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