SO I BOUGHT A 89 5.0 AND I HAVE TWO PROBLEMS(I'M SURE THEY ARE RELATED).... THE FIRST PROBLEM IS IT RUNS VERY COLD......MOTOR COLD AND INSIDE COLD.....I HAVE CARDBOARD OVER COMPLETE RAD AND STILL ONLY RUNS ONE TICK OVER COLD( IN TOWN COOLS DOWN ON HIGHWAY WARMS UP A BIT)....I PUT IN A THERMOSTAT AND A HEATER CORE WITH NO CHANGE......THE NEXT PROBLEM IS FUEL MILEAGE.....13.25 GAL TO 110 MILE (SORRY DID CONVERTION...I'M IN CANADA)...50 LITER TO 250K....O2 SENSOR WAS BAD SO I REPLACED.....I HAVE CHECK NEW ONE WORKS FINE AND FUEL PRESSURE IS GOOD.... ANY THOGHTS...THANKS... OH I CHECK TUNE AND TIMING (BASE) IS AT 14

 

Did it break your caps lock, too?

Did you get the thermostat in correctly? What do the sensors read, especially the ECT? You would be correct to assume the cold engine is causing the poor mileage. A properly working cooling system won't need cardboard over the radiator, especially with a gas engine.

 

thermostat is in properly...and it's the third one..... no the ect reads cold all the time.... the only thing the first owner put in was a water pump....and I do think the two are related...I thought maybe he put the wrong pump in(flow)....and it's pushing the stat open....might try a clear hose to see flow....it's only about-5*C sorry don't know the convertion....and even with the cardboard it's only running about normal(half way) on gauge.....I hooked up my A/F meter out of my Capri and it's showing good....