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Car Forum / Pontiac / Pontiac Fiero / July 2005improving fuel economy
Hi, Recently acquired '86 SE V6, and am surprised/disappointed by lack of fuel economy. Orig motor with 145K miles, but runs beautifully. Great at idle, bogs slightly and briefly when throttle opens, some of the time. Thermostat appears to be defective as it never passes 1/4 of its range (can't recall temp numbers right now, sorry!). I'm averaging 19 mpg with moderate driving, and given the weight of the car, was expecting a little more. Is this a little low, or average? Haven't done anything to car yet, but plan on replacing thermostat and air filter. Others? Will high perf air filter improve economy further? Many thanks! > Hi, Recently acquired '86 SE V6, and am surprised/disappointed by lack > of fuel economy. Orig motor with 145K miles, but runs beautifully. > Great at idle, bogs slightly and briefly when throttle opens, some of > the time. Thermostat appears to be defective as it never passes 1/4 of > its range (can't recall temp numbers right now, sorry!). I'm averaging that would be 195 degrees, right on the thermostat setting > 19 mpg with moderate driving, and given the weight of the car, was > expecting a little more. Is this a little low, or average? Haven't > done anything to car yet, but plan on replacing thermostat and air > filter. Others? Will high perf air filter improve economy further? > Many thanks! If this is in town mainly stop and go driving, it is normal. If it is highway cruising, constant speed it is low.  SignatureRobert W. Hughes (Bob) BackYard Engineering 29:40.237N, 95:28.726W or perhaps 30:55.265N, 95:20.590W Houston, Texas "The city with too much Oxygen" rwhughe@oplink.net >Hi, Recently acquired '86 SE V6, and am surprised/disappointed by lack >of fuel economy. Orig motor with 145K miles, but runs beautifully. [quoted text clipped - 6 lines] >filter. Others? Will high perf air filter improve economy further? >Many thanks! Temp gauge only goes a quarter of the way you are lucky don't mess with it or the thermostat sounds like that is fine. Air filter if dirty should be replaced that will eat up a little extra gas and pep. My 4 cyl does not get much more then that. I have an 88GT and I have always gotten 22/28 city/highway mileage and all is stock on the motor. Check your service engine codes to make sure one of the sensors isnt throwing off the ECM then try doing a tuneup on it including the air filter. I agree with everyone else, the thermostat is working fine at 1/4 of the guage reading. Get someone with a laser spot thermometer to find out what it's REALLY running at - don't trust the gauge. If you're not getting above 180F, you'll not come out of the enrichment table - and you're going to get the mileage you're saying. Hook a scan tool up to it also, and see what the ECM thinks the engine is running at. Seen more than one defective temp probe. > Hi, Recently acquired '86 SE V6, and am surprised/disappointed by lack > of fuel economy. Orig motor with 145K miles, but runs beautifully. [quoted text clipped - 6 lines] > filter. Others? Will high perf air filter improve economy further? > Many thanks! > Hi, Recently acquired '86 SE V6, and am surprised/disappointed by lack > of fuel economy. Orig motor with 145K miles, but runs beautifully. [quoted text clipped - 6 lines] > filter. Others? Will high perf air filter improve economy further? > Many thanks! The car's heavier than you might think, close to 3,000 lbs fully optioned. Is yours an auto or stick? Your mileage is about right for an auto, you should be able to hit the low 20's on the highway with steady state cruising. If the thermostat isn't working properly then yes, mileage will go down as the ECM is programmed to provide more fuel when the engine is colder. Proper thermostat temp is 195°F. The air intake system on the Fiero is very well engineered, a so-called "cold air intake" actually increases the intake air temperature and won't increase performance or efficiency at all. Never hurts to change the fuel filter. Be sure to spray some PB Blaster on the fittings a day before you start, and use only flare nut wrenches or you'll damage the fuel lines. More info at http://www.fiero.nl JazzMan Signature********************************************************** Please reply to jsavage"at"airmail.net. Curse those darned bulk e-mailers! ********************************************************** "Rats and roaches live by competition under the laws of supply and demand. It is the privilege of human beings to live under the laws of justice and mercy." - Wendell Berry ********************************************************** thanks everybody. Its an auto, and the past two weeks I've been doing more highway cruising and seeing an increase in economy. Sounds like my sweet little car is running pretty sweet. I'll still swap the air and fuel filters (reg maintenance, they're probably due), and get the codes checked. Thanks again! |
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