Something's odd! Shifting unusually.

I just made the move from Chicago to Denver. Drove the whole way, no problems.

Now that I'm here, it seems that the transmission is acting weird at low speed; it's like it doesn't know when to switch between first and second when I'm coming into my neighborhood. It'll be at too low an RPM, then sorta chug down into first.

I've covered for it by driving it in Performance Shift mode, which seems to make all better.

Also, I've only been able to find 91 octane gas here thus far. Will that cause issues?

Im assumeing you have a GTP then if your worried about the gas Octane?

I believe 91 is lowest GM requires...so you should be ok there..

as far as the tranny....Im not sure but I am sure someone will have an answer for you!

That is a good assumption! I have a 99 GTP.

I also notice that the boost gauge really starts lighting up faster here, as well. Do you think that's normal?

That is a good assumption! I have a 99 GTP.

I also notice that the boost gauge really starts lighting up faster here, as well. Do you think that's normal?


The stock Boost gauge is not reliable...I wouldnt trust it with my life!

I run 89 octane in my 99 GTP with no problems.

Anyway, as for the tranny...how many miles does the car have? Is it around 100K? If so, you may need to have your transmission fluid and filter changed.

I run 89 octane in my 99 GTP with no problems.

Anyway, as for the tranny...how many miles does the car have? Is it around 100K? If so, you may need to have your transmission fluid and filter changed.


your flirting with disaster if your running 89 octane!
I bet your getting mad KR!

I haven't had any problems...I have issues if I run 87, which is regular unleaded where I live. 89 doesn't...at least not that I've noticed. Supreme is 93. I haven't been able to afford supreme lately...but now that prices are going down, I'll probably start using it.

the reason 89 octane gas is bad for our cars is that we have a supercharged engine. when you supercharge an engine, you automatically increase the load and therefore the heat in the cylinders. When the cylanders become hot, detonation can occur.

Detonation, if severe enough, will burn a piston. Detonation is also known as Knock.

Our PCM (the car's computer) will listen for knock and if it senses it, it will reduce (or increase?) the timing, thereby reducing the power the engine is producing, and killing performance. This phenomenon is known to us GP'ers as Knock Retard, or KR.

Knock retard is a safety measure put in by gm to save your engine from grenading when you put in crappy gas.

This is nice to know. I just bought my 97 GTP in Apr. and have been burning 87 which is the mid grade here in Nebraska. This car has been really well taken care of and I want to keep it in nice condition. I will start putting 91 in it. We haven't put 1000 miles on it yet. The car has 114k. Does anyone have any other care tips that they would care to share. I have been reading about changing the oil in the cone. That doesn't seem to difficult.

I've got 58k miles on it :( The best way to describe it, and this might make sense to only me, is that at low speeds, it's bogging down. Does that make sense?

when i drove through denver in my GTP full of my stuff. My buddy and I noticed the same thing the boost was coming on a lot earlier when put under a load! We came to the conclusion thiner air. Higher Altitude. Flagstaff AZ was the WORST.

This is nice to know. I just bought my 97 GTP in Apr. and have been burning 87 which is the mid grade here in Nebraska. This car has been really well taken care of and I want to keep it in nice condition. I will start putting 91 in it. We haven't put 1000 miles on it yet. The car has 114k. Does anyone have any other care tips that they would care to share. I have been reading about changing the oil in the cone. That doesn't seem to difficult.

Change the superchrager fluid. I just changed mine 2 days ago once again and it looked like old used oil from the engine (color of it) it had 32k miles on it. Im now running 2 bottles of fluid instead of one.

I have ran 87 in my car before when i first bought the car didnt know anybetter till i looked at the gas lid and it said to run premuim. Ohh and this past august had to run it agian in AZ the had a gas main break between pheniox and Tucson. Got gas 87 only Avialble -found the nearest WALmart and got some octane booster. and drove until we got to are destination. run fine though

I've got 58k miles on it :( The best way to describe it, and this might make sense to only me, is that at low speeds, it's bogging down. Does that make sense?

Mine was bogging down at low speeds too...took mine yesterday and had fuel filter replaced and trans fluid/filter changed. My shifts cleaned up noticeably, and my car isn't bogging down anymore. If your car has been driven in an area where it's had to pull a lot of steep hills or other conditions that cause the tranny to shift a lot, the owner's manual says service the tranny at 50K. Check your fluid, if it's a bright pinkish red, it's fine, but if it's brown, I'd definitely have it changed or cleaned. Most dealerships now clean it and pump it back in. And I'd have the fuel filter replaced, just to be safe...if it clogs up and the pump goes out, you're gonna be shelling out a lot of money.