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2006 grand prix "pulsing"

E

EMKETART

New member
I have a 2006 Grand Prix 3.8 that just rolled over 200,000 miles. Within the last 2,000 miles it "pulses" when going up hills. It seems like when I start going up a hill right around the time I think it is about to shift down it starts pulsing. It acts like it is going to speed up, then it slows down, then speeds up then slows down and so on. Kind of like NNNNnnnnNNNNNnnnnNNNNnnnn if that makes sense. It cycles through the speed up / slow down probably about once per second if not a little faster than that. It is fairly slight and hardly noticeable although seems to be getting more often and more noticeable as of late. Any thoughts or questions?
 


Sounds like it's fighting the torque converter, it can't make up it's mind of if it should downshift of not.

Just remove your foot from the gas and it'll unlock the converter and get back on the gas again. Also at that mileage it's likely getting worn out and it could be more than just it fighting unlock the converter.
 
When was the last time the plugs/wires were changed?

I also had a similar issue when my cat was clogged up on my 00 GT. Once I changed it out and gave it a tune-up it finally quit doing it and downshifts like it should when under a load.
 
I had exactly this problem in my 1997 Bonneville SE (non supercharged L36). Plugs and wires did not change anything. Eventually the transmission started throwing a P1870 DTC around once every month or two. That's a code for slipping transmission components. There in an internal valve that regulates the amount of fluid going to the torque converter clutch. When the valve wears it starves the converter and the converter stops locking up. You have to remove the valvebody to replace it, which is expensive. I opted to just clear the code whenever it would set, and continued driving the car for 6 years. If you give it a little more gas when it starts doing the pulsing thing, it should stop pulsing. I recommend just doing that until you're ready to spring for a trans rebuild.
 
Fivefingerdeathpunch said:
Sounds like it's fighting the torque converter, it can't make up it's mind of if it should downshift of not.

Just remove your foot from the gas and it'll unlock the converter and get back on the gas again. Also at that mileage it's likely getting worn out and it could be more than just it fighting unlock the converter.
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This
 


Like another poster mentioned, I would look at plugs, wires, and coils. I would especially look at the connection where the plug wire connects to the coil, takes just a moment and I have seen corroded coil lead cause this issue. The key to your symptom is that it happens under load, such as going up a hill. On the 3.8 this often reflects a lack of proper ignition in one cylinder.
 
All good stuff. Thanks everyone. I've owned the car for about 30k and haven't done anything to it. I will check the connections and give the break tapping a try.
 
my only other input is that the transmission with that high mileage is probably having some TCC solenoid issues. Very similar to the "hunting" that people have described, cruising 60-65 mph at about 1800 to 2000 rpm and the needle will jump up and down 200 rpm.
 


UPDATE - I have replaced plugs, wires and coil. None of them helped. I still have the same problem. Removing my foot from the gas (or tapping the break) to unlock the converter does not work. I plan on taking it to transmission dude to have him check it out. Any other thoughts would be appreciated.
 
Mine just started doing the same thing. Sounds like an issue with the TCC solenoid or the torque converter itself. You might want to take a trip to a transmission shop.
 
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