Guys. HORRIBLE HORRIBLE GAS MILEAGE. What tests can i run to diagnose the problem. I got less then 200 miles to a FULL tank. I though the first couple of tanks were going quick because of me adding all the cleaners and the seafoam treatment i did.

My car was running a high idle irradicaely. Around 1000-1200. After Seafoam cleaning and checking all plugs. My Car Purs at 700-800 rpm.

So i know my idle isnt too high. What else can it be? Can you guys throw suggestions at me to check when i get home tonight? Thanks guys. (Fuel filter, Spark Plugs)

 

definitely check your plugs, their condition will tell you something about what's going on in your engine.
Sounds to me like you're running rich. Clean your air filter/s, have your timing checked, i would also do a thorough cleaning of the MAF connector and the TPS connectors.
Only other thing that comes to mind might be the FPR, but check those other things first.

 

yea when i changed my spark plugs i didnt gap them. I was runnin really rich and was gettin and 80miles to a full tank. Then i gaped them and was gettin about around 250 on my NA

 

Bad O2 sensors could also contribute to poor mileage.

 

Another thing to check will be your coolant temp sensor..when my cars sensor went out. It made the car run rich by dumping too much fuel in.
What do u classify as a full tank of gas? I just found out that the Z cars have a low fuel light. Prior to this I was only filling up about 12 to 13 gallons of gas. and I was gettin around 220 miles on a ful tank.