Converter lockup

I have a 99 Grand Prix GTP. Whenever i dont drive it for a a few hours and it is completly cool (sitting over night for example) then the next time i drive it the torque converter will not lock up for about the first 20 minutes of driving it so im pulling way more rpms then i should be. Once it finally decides to lock up it works fine for a little while of normal driving but then slowly starts to lag. What i mean by this is the converter will lock up when it should but really freaking slow, by the time it locks up i hit overdrive. Does anyone know what causes this and any possible solutions? I just changed the filter and had the fluid exchanged so it is at the proper level. Any help would be appreciated thanks. Gas is way to expensive for this. 92000 miles

Hello;
Recently (few mnths ago) I had experience similar (lack) of performace with my 2001-Grand Prix GT. The filter etc was changed (similar to your actions) whereby the car was lagging on the open freeway whereby the engine would go into overdrive and sound as if it would rip right outta the hood and the engine light would soon show indicating that the engine is over-heating, though coolant level reasonable.
I took the car to my local Dealership -Roy Foss whereby it was discovered that it was the "Catalytic Conerveter". They explained that this is common whereby upon inspection it was noted to resemble a piece of 'coal' and/or dog-s***! They held up a new* Catalytic Converter whereby it was suppose to resemble a finished-steel honey-comb part for rear exhaust. The engine was running but the car itself was choking.
The car now runs insanely fast as this was the reason I initially purchased the car as I do alot of freeway driving and it performs amazing on the open road.
The catalytic-converter was also covered by my Warranty* which fortunately I had ex-tended*.
Just my bit of input. Mancini :smokin:

Thanks for your input. But what it is with my car is the torque converter does not lock up like it should. Instead if it feeling like your grabbing another gear it is real slow and laggy. You can watch the tach when it starts to lock up and it will SLOWLY drop in rpm until it is fully locked up. By this time im ready to shift into overdrive. The car has plenty of power though so it is deffinitly not an engine performance issue. If there is any transmission gurus on this forum i could really use the advice. Thanks

There are two possibilities. One the TCC solenoid is going bad and will need replaced. Two, the PCM needs to be reset so that the signal to the TCC will be sent properly. You can reset it to stock settings by unhooking the positive battery terminal and allowing it to sit for a few minutes. This will return the setting to stock and may help the problem. If the solenoid is going bad then it is not an expensive fix.

Thanks GTP dad,

OK its definitly not the computer because i have already tried that, I left it unhooked overnight hoping it would cure the problem. Do you know how difficult it is to replace the TCC soleniod? Is it something that i can do on my own or would i have to take it to a tranny shop? And about how much would you think? Let me know thanks.

I would take it to a tranny shop. They can replace it in about an hour and will have the part available. The part costs $50 to $60 and the labor will vary depending on the shop. Expect a bill less than $150 for the repair. I have changed them in the past but not on this model transmission so I am not certain what is involved. The one I did cost $47 for the part including the gasket.

Have you had the car scanned? The computer tells the TCC to lock as you know. There are a few conditions that are required for the TCC to lock (one is that the car must be operating in closed loop). With all the gizmos on these cars now, it is really hard to tell what is engine and what is transmission with out a good scanner (not a code reader). If you can see if the TCC is getting a request to lock and the rpms are still up, you will know its tranny related.