Fuel Mileag

Does this sound low to anyone? Last week my wife and I took the 88 TC on a trip to Charleston, SC which was mostly interstate driving. The car drove and performed well. I kept the speed around 75-80 mph. When it was time to fill 'er up with gas, I checked my fuel mileage and was shocked to see that I only averaged 23 mpg. I usually get 18-20 mpg around town. Could there be something wrong that I am not aware of? Is so, what do you think?

On a separate note. I recently replaced my heater core. Now I have no heat while driving. If the car sits and idles, it will heat up and the temp gauge will read as normal. Once I start driving, the hot air turns cool and the temp gauge drops. I have also replaced the thermostat..192 degrees, and the water pump trying to chase down this problem. Any thoughts, as I am freezing my xxx off? Thanks in advance.

You mileage sounds a little low to me. Most people here report mileage from 25 to 30 or a little better. for sustained highway trips. How old is your tuneup and what parts are in it. Air filter dirty? Timing? Could be lots of other things too.
Pull the codes and see what comes up. There are articles for this stuff in the Technical Articles.

Take the hose off the FPR and see how strongly it smells of gas. Light smell is OK but strong smell or liquid gas means the FPR is bad. Could still be the FPR. Run the fuel system diagnostics.

Heat problem still sounds like a thermostat. Did you check the new one in a pan of boiling water .
T-stats have been known to be bad right out of the box

Low mileage and running cool could be related. If the car isn't warmed up it might be running rich, lowering mileage. Check your plugs for further proof.

+1 on thermostat. I bought 3 last time to get one good one!

I did a tune-up in May..autolite plugs, new wires, new distributor, new timing belt, K&N filter recently cleaned, cleaned IAC valve, cleaned the throttle body..ect. The car cranks on the first turn of the starter and idles steady at 1000 rpm and runs well. I did just replace the gasket between the exhaust manifold and the turbo housing..it had a serious exhaust leak. I get good boost and the car does not have any drivability problems. I have noticed since the heater core replacement, that the slide for the temp control will not move all the way over to cold and moves back a little when slid all the way over to hot.

I must be one of those that gets poor mileage on my TCs. I had an 88 White TC, boost set at 18 PSI with a K&N homemade cold air intake. At 75-80 I would get between 21-23.

My current all stock 88 TC before I changed the tires to 245/17 Fr and 275/17 Rf would get 25-26.

88Phoenix, did you pull the codes?

Originally posted by Pete D:
88Phoenix, did you pull the codes?

Have not had time to do that yet. I will have to use my mechanics scanner tomorrow when he is at the shop.

Pull the codes yourself.... it is easy.... see the tech articles.