Th other day I was driving my car and I noticed that it had alot more power than the day before. My fuel economy is down a bit but now the wheels will chirp when the tranny changes gears at half throttle. I went around a turn yesterday at about 15 mph, gave it about 1/3-1/2 throttle and the car accelerated to 55 mph in 2 1/2 seconds.

I also noticed that the car runs alot smoother now too.

Does anyone have a clue as to what this might have been? Clogged fuel injector maybe?

 

maybe, cant really say unless you tell us how it was running before. Did you have any noticeable/strange vibrations coming through the car that would sugest a lagging cylinder?

Also know that if its cold where you are colder air is denser so you could definitly have a 10-15 hp gain on very cold days.

 

Yeah, as Doug said, usually before the CTS really reads warm on a cold day, you get more timing advance and more fuel and that denser cold air all add up to a good gain in HP. And if your car is close to making decent power, it'll kinda push over that hump and it'll break the tires loose easier.
Might be good to change the fuel filter and if you have an AFPR bump the fuel pressure + 2psi, and check your timing, maybe bump it up a couple of degrees.

 

OK, the other day when I noticed this it was 70° and about 70% relative humidity which was about 30° warmer than it had been. The car had been idling a little rough and had a slight hesitation to it but she was still fast and would still fry the tires.

 

The temp today was only in the mid 20's and it is still doing the same thing.

Even after driving for 20 minutes at 60 mph.

 

"Calm before the Storm".....




Lol! J/K,could be any number of reasons,need more data to tell for sure.

 

Wish I had more data to give...

All I know is that the car had been running a little rough since I got it in June and had something that reminded me of a miss. The other day, all of a sudden, the car was running smooth as silk, with no miss, the exhaust smells better (as far as exhaust goes), and has power to spare.

The only downside to this is that it is now using more gas.

 

How much more? 1-2 gals per fill-up,or MORE like 1-2 fill-ups per miles?

 

Did you change gas stations?
I went to Shell from brand "X", and noticed a big jump in throttle response, I too believe it cleaned my fuel system, and also think it had a more reliable octane content. (Just half way through one tank of premium, it woke up!)

 

Getting less miles per gallon and I am still using the same brand of gas.

 

Does your SES light come on,are you getting any codes? Sounds like maybe the ECU is in Limp Home Mode so you are running rich. That would explain the drop in milage and the increase in power. This could be brought on by a bad chip also,and usually the SES light will be on,check and make sure the light IS working.

 

No codes, no lights, nothing. All lights work.

 

Maybe it's using more gas b/c you're frying the tires everywhere?

 

No, I don't do that very often.

 

I'd go back and check the "Throttle Position Sensor"(or TPS), if it somehow is reading high it will richen the fuel even at half throttle, or it could make it a lot leaner. It just depends on what it reads at idle.
"MAF" type EFI is usually .54 volts at idle @ the sensor connector either measured by the center wire and one of the other two, or with a scanner.
"MAP"(Speed Density) is usually .70 volts at idle.

You might want to set the "Idle Air Bleed" or basically the position of the throttle opening at idle.
To do this you need to access the ALDL as if you were checking codes. While the ALDL connector is still shorted, wait 30 seconds and unplug the IAC motor on the throttle body. (This makes sure the IAC pintle(point) is fully seated and won't let extra air in as you set the "I.A.B."(Throttle Position)
Once that's done, turn off the key and remove the short at the ALDL. Then start the car, if it won't run on its own, "overadjust" it to raise the idle high enough to run. Then back the idle down to the spec on the VECCI label under the hood.
(Make sure the car is fully warmed up before beginning.)
When finished, turn off the engine, clear the memory and reconnect the IAC. Restart it and allow it time to readjust and learn the new position.