Thread: 2005 Grand Prix Losing power

While driving home the other night I tried to accelerate and around 3500 it felt like the engine shut off the came back on. It's not like a miss it just shuts off. The tach will drop all the way down to 500 the take back off and go back to 3000 then back down. No check engine lights my friend hooked it up to a tech 2 and everything shows normal. Hooked up fuel gauge and drove it and read 62 pounds when it was doing it. Thought it was the converter was plugged so I replaced it still no better. Any suggestions? It has 280,000 miles on it trans was rebuilt about 40,000 miles ago.

I had a problem like this and it turned out to be a bad crank sensor. This was actually the 2nd time I had replaced it. The first time it did trigger a CEL and code. I did the wrong thing in fixing going with a cheap sensor, not AC Delco. Low and behold I had some issues creep up when I replaced the harmonic balancer. This time I was getting extreme poor driving and stalling only when the engine was fully warmed up. I had no code or CEL at all. I actually took it in to Firestone and none of their diagnostics came back. All they saw was a slight variation in the CPS sensor but it wasn't enough in their opinion to be bad, their recommendation was a bad ignition module. I did that and it didn't fix it, I then replaced the CPS sensor, with a high end name brand, as well as the ignition harness to boot. Hasn't come back since

I would put money on the CPS sensor. I would say replace the CPS and see if that does it. The tools you need can be rented at autozone including the bolts specific for the GM crank pulley in order to pull it off. Pneumatic tools or battery powered pneumatic wrenches are desired, I also think you can get the 27mm or so socket you need for the crank bolt at AZ too.