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Engine rev's up and down at stop/idle when warm. (Long Desc)

its called a security torx bit. i cut a slot across the head and used a flat head screw driver to take the screws out of mine.
 


Looks like the local autoparts place has a set of 8 security torx bits on for $10, I'll just pick up a set of these. Thanks for the input.
 
I started seeing something like this with my GTP. For me, it only happens during cold startup and once the engine reaches a certain temperature, the idle surging stops. When I scanned it with HPT, I see the O2 is reading rich initially and slowly leaning out but not switching up and down yet. Then, the PCM starts switching back and forth between FTC0 and FTC2. The two FT cells have different LTFT adjustment values...so, this is what I think is causing the idle surging. Basically, one FT cell adds or pulls more fuel than the other FT cell.

So, what is causing the PCM to switch FT cells at idle? Using TinyTuner to peek deeper into the PCM, I noticed some settings that seem to imply if the O2 sensor is not switching fast enough, then the PCM will command this FT cell change.

...so, how to fix it? I am not sure. I already put in a new AC Delco O2 sensor. Is it the wires to the O2 sensor that are tired and not letting the O2 warmup fast enough? I have TOGs with an extension harness but I have had these for a couple years already before this surging started.
 
My issue only happens when the engine has been running and is up to operating temp. I'm also throwing P1133 and I've already swapped out an apparently perfectly good working Denso O2 sensor for a Bosch, same issue. I DO have something going on with an exhaust leak, which could cause P1133, but I don't know if the exhaust leak is also causing my idle problem. The idle issue I have is the same as the OPs, in that after the car is warmed up, it'll start revving up and down +/- 500 rpm until the car eventually dies.
 
I definitely want to fix the exhaust leak. I was trying to decide if I wanted to do headers or ZZPs powerlogs. The headers would be cheaper by more than half, so we'll see what happens I guess.
 


Hi all, thought i was the lone ranger. Having this exact issue myself. Diff is im getting a dtc of p0300. Gonna try all your ideas. Thanx OH YEAH, MINE ONLY HAPPENS WHEN ENGINE IS COLD.
 
Alright, hello everyone! Updating everyone on the crazy idle problem!
so, i replaced the bad axle and hub assembly on the front passenger side and then drove the car 3hrs to my dad in AR.
During the entire trip, and ever since (almost a week) i haven't experienced that crazy idle issue again! The car has been driven all over town by myself and my dad a good bit and neither of us have experienced it.
 
Nice! I cleaned my MAF sensor, and my issue got a lot better. I'm also going to replace the IAC valve (this weekend) and I'm hoping that'll take care of the rest of the issue.
 
The torx is a security torx, some security anyone can buy them don't know why they were used. I have this same issue. I was pulling a p0171 code. I havent cleaned the MAF Every after the cleaning I fixed my p0171 and the car runs great after it warms up but before it gets warm idle is rough and really low around 600. wants to die but keeps its head just above water. I am like you don't want to pay the money for a 100$ MAF. I am hoping it works it's self out
 
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