Alright guys here the thing i own a 01 monte carlo 3800 and for some odd reason i am only getting about 200 miles per tank city driving and i have not idea why. I just got the oil changed and spark plugs put in. About two days ago i sea foamed the car. And for some reason my gas gauge keeps going up and down up and down. The mods i got on my car would be CAI, throttle body spacer, and MSD wires. Can anyone help me out with what could be the prob. damn gas prices are crazy.....

 

how many miles are on the car? it could just be getting old... my parents have a 43 gallon tank in their suburban with 254000 miles and it gets about 450 miles to tank if it's really lucky (something like 12 mpg, used to get 16 on a bad day). might be getting old. is it running smooth? no gas leaks anywhere? maybe it's leaking somewhere.

 

car has about 85k and nope no gas leaks anywhere i puzzled by this. car runs smooth and idel smooth. only mechanical work done to this car is had to take my car to get the valve machined because it wasnt giving me compresion on piston #5 but thats about it engine wise... had power stearing pump replaced three times

 

hm... one cylinder wasn't giving compression so a valve was machined... okay, not a biggie, but usally the cylinders wear evenly. you said valve.. did you mean valves or was just the one valve machined? usually if one cylinder gets worn down and isn't getting compression the rest are only a good several thousand miles behind it.

 

well they machined the back valves..... when they did that they changed plugs and all spark plugs were down to nothing

 

check a clogged fuel filter and for an intake leak.

 

how would you check for an intake leak?

 

Have you tried changing gas stations? I heard some of them were mixing in the corn fuel and selling it as regular even though it's illegal. They make more and you get less mpg.

 

Could also be the spark plugs, I used to have a Chevy Blazer, and those trucks hate Bosch plugs with a passion, poor economy and misfires were common with them.