So i have two very important gripes about my obs in its current form, two problems that annoy the **** out of me and i cant seem to figure out what they are, so feelers are going out here too...

Problem #1 and the one that can ruin my day just by being there.....
When my motor is cold, and the problem gets successivly worse as the motor is colder, i often give it a little gas to bring down the idle rpms from 1500 or so to 1 grand or just under (a habit i picked up from my gmc sonoma). At this point, espically inbetween 750 ish and 1k rpm, there will be a shaking that feels like a misfire, though it does not throw a cel at me. There are times when it will feel like a damn earthquake is hitting the chassis of my car, other times its not very noticeable, but it is always there. I have done a full tuneup (which i paid someone to do the first time around cause i did not know how to change my plugs yet ) After pulling the unfriendly plugs and replacing the knock sensor that went with it, it threw another cel and i found out my front 02 had failed. So, new o2s, new plugs and new wires later, it refuses to go away, and i am livid....Once i give it gas, smooth as silk....

The second is a fleeting issue as i do not put a lot of miles on my car. I do a good mix of freeway and city driving, though city driving is more common, yet no matter how hard i try, i cannot seem to wrack up more than 20mpg. Usually i use 1,2,and 3 a hell of a lot more than i do d, and i usually shift just under 4grand, but even in d with tranny shifting at barely above 2 grand, same problem..... ideas guys?

 

The shaking is caused from the motor being an H4, which is normal. Sometimes when its cold it will do it a little worse.

Automatics are set up for less mpg than a manual and to get 20mpg is about normal unless your driving all highway. Not sure if the plugs are old or maybe you lose some mpg's with just the car being a little older, but 20mpg average, may not be what you want, but is normal for the car you drive.