Terrible gas mileage after head rebuild

My 91 DX wagon was getting a little sluggish and my friend does head rebuilds so I had him rebuild mine. Anyway I use to get about 25 mpg and I was hoping for better, but since the rebuild I have been getting about 20 mpg. The car runs strong and isnt throwing any codes so im really confused. I replaced the pcv valve and have done a full tune up recently (plugs, wires, coil, rotor, cap ect.) The only engine upgrade I have done is a cold air intake but that was done a long time ago. The only other problem is a slight fluctuation in my revs at idle. I have read that could be the IAC valve so i pulled one for the pick your part and there was no change. I dont know what else to try or what else it could be. Please help

Any ideas would be appreciated

My wagon-
1991 Civic Wagon
D15B2
Automatic
182,000 miles
head rebuilt 400 miles ago

One last thing. My trans is starting to go out so it slips a little going into second and third but not alot

Comments

  • HakosukaHakosuka Wagonist
    Mayxbe your clutch went, if you say it slips...
    If you step on the gas and brake, do rpm's rise?
  • wagovanloverwagovanlover New Wagonist
    Well like I said it's an automatic so if it's in drive and I hit the gas and brake the rpms will rise. But either way the transmission is barely slipping, and was slipping before when I was getting much better mileage
  • Did you check your PCV valve this can have an affect on gas mileage too. Mine was completely clogged and after I changed it it went up to what it should be.
  • wagovanloverwagovanlover New Wagonist
    Yeah if you read my original post I already replaced my pcv valve and I checked it again recently just in case
  • ZippergutsZipperguts Band Wagon
    Two things to check:
    1) Timing belt marks
    2) Valve adjustment
  • wagovanloverwagovanlover New Wagonist
    I will check that and let you know. I thought the same about the valve adjustment, hopefully your right
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