Engine and MPG problems

[jedi]

Ok, I got a strange one for all you mech heads. Recently my MPG went down from around 22mpg to right now it sits at 17.4mpg avarage. When this first started happening I took it to my dealer who informed me my waterpump had gone and took my optispark with it. (I think they went to Maui together and won't be back). Anyway, the car seems to run a little rough and I "sometimes" see "light" smoke coming from the exhost (kind of like what happends when it's cold out so it is not a significant amount). The dealer supposedly checked it out when they had the car in for the waterpump and optispark situation and said there was no problem. Any suggestions?
Jedi

 

[Chick]

Can I have the mileage on your car and the temperature you say is 'like when it's cold out' like winter cold?...

In cold..... a car will typically get less mileage in the winter... a known fact! Easily expect 3 to 4 miles less per gallon... that said there may be nothing wrong with your vette.

 

[jedi]

Naw it was like 60 something degrees outside and 8 at night. The miles on my vette is around 60K.
Jedi

 

[Chick]

Thanks for clarifying the weather condition...

I'd want to see what the O2's are doing. The O2's control the mixture and if they're not doing what they are suppose to it can cause the car to use more fuel.

Also run a can of injector cleaner through it (GM in the 20oz can or Chevron Techron) same stuff.... Chevron makes it for GM. Because it has about 60 on it and it's time!

 

[jedi]

Thanks, I will pick up the fuel injector cleaner today. Should I take it back to the dealer to check the Oxygen sensors? Or is that something I can check on my own?
Jedi

 

[jedi]

One more thing!

Would it be better for me to have the injectors cleaned at the dealer? I think it's about $99 Clams.
Jedi