RPM, Cruise Control and Gas Mileage Problems

[alero2002V6]

1. The Cruise Control Turns itself off if I am driving on an upslope.
2. There is a constant stuttering of RPMs as if I am playing with the pedal.
3. Low gas mileage 18 in the City. 20 on Highway.
4. Replaced Fuel filter, changed engine oil, used additives with fuel to clean heads, fuel system. No results.
5. The Car was driving at high RPMs for 60mph. Usually its about 1900RPM for 60-70mph. But was driving at 2500rpm. Changing Fuel Filter fixed it. But still have stuttering RPM problems.
6. Its a 2002 Alero 3.4L V6 Coupe with 92,000 miles on it.

[BNaylor]

Sounds like it's misfiring. Have you tried new spark plugs and ignition wires? Also, even though you ran fuel injector cleaner through you could still have a bad or dirty fuel injector. Plus you can test the fuel pressure at the injector rail just to make sure it's not a fuel pump or fuel pressure regulator.

Do you ever get the SES/CEL light?

[alero2002V6]

I took the car to the dealer today. He suggested that we run a Computer Check on the car to determine the problem. He also suggested that he would disconnect the fuel supply from the tank and connect a solvent to the engine from the rail and run the car on it. He also doubted that the fuel injectors are not supplying the fuel properly. Does this sound right? He did not have an answer for the Cruise control turning off. I dont have any engine check lights coming on. I have not changed spark plugs or the Ignition wires yet.

[BNaylor]

Originally Posted by alero2002V6

I took the car to the dealer today. He suggested that we run a Computer Check on the car to determine the problem. He also suggested that he would disconnect the fuel supply from the tank and connect a solvent to the engine from the rail and run the car on it. He also doubted that the fuel injectors are not supplying the fuel properly. Does this sound right? He did not have an answer for the Cruise control turning off. I dont have any engine check lights coming on. I have not changed spark plugs or the Ignition wires yet.

Probably a good idea to have the dealer run the Tech II machine on it. It may reveal some DTC error codes that do not trigger the SES light.

The dealer's method of cleaning the fuel injection system is better than running additive via the gas tank. It's more effective. According to GM, 6 out of 10 injectors suspected to be bad are just dirty maybe from using less than top tier gasoline, etc. Personally, I doubt the fuel injectors are bad but you never know on an Alero.

The cruise control could be dis-engaging because a misfire is being detected but not enough to trigger the SES light. Also a good idea to change the plugs and wires because of your mileage. Good luck!

[alero2002V6]

I got the car checked by a few other mechanics. Finally it was diagnosed that the intake manifold was bad, in addition to the thermostat not working properly. Both of these was fixed. I am still having rpm fluctuations, even though the gas mileage has improved from 19mpg to 25mpg.