bad mileage, where else to look?

I managed to get a new cat on the 95/HO/auto 4x4, used a hiflo magnaflo (i think it was) also replaced the O2 sensor and welded up the ehxaust leaks. I unhooked the battery for several hours to reset things, and previously R&Red the plugs etc. After rehooking the battery and starting it, it now starts much quicker and runs quite a bit better. But... my mileage is still 15, Ive got 18/20mph for months. I refuse to have any of the parts swappers try to diagnosis it. Where else should I look. I dont smell fuel but it looks like its rich from the tailpipe.
Thanks.

Sticky injector, bad MAT sensor, have you cleaned the TB? You might also consider going synthetic for the diffs, a little less resistance esp in cold weather. Stupid question but how is your air filter?

coolant temp sensor? Maybe the ECU is stuck in open loop. Should be able to test it with a DMM, not sure of what the ohms would be though.

Next step after all basic maintinance items are good is to look at weight reduction(keep only 1/2 tank of gas, remove as much as you're willing to from the interior, clean all mud from wheels, fenders, underbody, etc) and airflow (ie, remove roof rack, spare tire if you've got it up there, repair/replace broken trim, etc)
I removed the rear bench seat, roof rack, and got rid of the 200+ pounds of stuff I've had in the back for years, and improved ~2MPG on the highway. (I put the seat back in, was way to loud and empty sounding without it.


HTH

B

Now that I think of it, last spring I replaced the fan clutch,rodded the rad,installed a trans cooler and new hoses and 195 thermo(all autistic zone parts). It runs under 210 now per the guage as opposed the old 210/215ish. I have questioned if its running in open loop or closed. I`ll infared the thermo housing to check the actual temp. Is there anyway to tell after a 40 mile to work drive without a code scanner chingas? Seems thats when I noticed a decline in mileage.

dyna said:

Now that I think of it, last spring I replaced the fan clutch,rodded the rad,installed a trans cooler and new hoses and 195 thermo(all autistic zone parts). It runs under 210 now per the guage as opposed the old 210/215ish. I have questioned if its running in open loop or closed. I`ll infared the thermo housing to check the actual temp. Is there anyway to tell after a 40 mile to work drive without a code scanner chingas? Seems thats when I noticed a decline in mileage.

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Is your torque converter locking up ok?

If you suspect it is running rich consider getting your injectors cleaned and flow tested. I would also tested what kind of fuel pressure you have in the fuel rail, maybe you have a bad pressure regulator.

Temp just dropped here pretty significantly in the past week. I got terrible miliage this week. My temp wouldn't stay up. Also I haven't gotten over 15mpg ever since I overhauled my cooling system either. Even in the summer the temp wouldn't even get to halfway when the thermo would open and it'd drop again.

I made a jacket today for the front of the radiator. It keeps the temps up higher and hopefully I'll get better miliage. I'll let you know how it works out.

Also I have a crack in my exhaust manifold that could be causing me to run a bit rich. That should get fixed over Christmas break.

Other than that I'd take the suggestions of these guys as well.

A cracked exhaust manifold has been known to screw up O2 readings and cause the computer to make the engine run rich.