ok-I'm starting to get fed up with this. Car is 89 740T wagon, 180K, AW-71, my first brick. Bought used, runs fine, no smoking, unusual smells, idles fine, pulls hard but getting 13-15 MPG combined driving and 16.5 highway!!! Things I've done to engine:
Full tuneup-everything replaced,timing done and ran Seafoam through intake.
All Fluids replaced including tranny
Replaced all skinny vacuum hoses, all coolant hoses, cleaned intake system including IAC,TB, all hoses and intake manifold.
Replaced fuel pressure regulator, fuel filter, and fuel pump check valve.
Replaced O2 sensor and FI coolant sensor
Thought I fixed it when I found:
Car had black ECT which is suppose to be for LH-2.4 cars, thought that was the problem and replaced it with blue one for LH-2.2..didn't help
Found leak in intake hose from amm to turbo- temporarily sealed with duct tape-no help.
With new FPR and check valve car no longer had occasional long cranking times-no help.
Things I've check:
No fuel leak
Tires, suspension and brakes fine. No locking. Only thing iffy is right front wheel seems somewhat tight. Can spin by hand but does not spin freely and definately feels tight, like when new pads are installed but not so tight that you would think would make a difference it MPG's.
Next on list to do:
Check fuel pressure-should be fine with new FPR but who knows...
Have injectors cleaned
replace intake manifold gasket
drop match in fuel tank if above doesnt help
Random thoughts:
You would think if nothing else replacing and fixing the above old and tired items would improve economy a little bit. Its actually gotten worse. My last tank since replacing the fpr and check valve got 15mpg of amost all highway driving. I'm starting to think its an air leak problem somewhere in the intake tract. Could a stuck open IAC be doing it? There was one time when the needle actually hovered at the 3/4 mark for about 25 miles before dropping like a rock again but I got my best tank at 17mpg. Seemed like something correctted itself briefly before going bad again. Anyway sorry for the length. I have 4 cars and I really enjoy driving this one but this fuel thing has taken all the fun out of it and I find it is the car of last resort. Any suggestions would be greatly appreciated.

Dave

PS-I am not heavy footed. These numbers are from driving for max economy

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Dave 89 740T Wagon 178K