StanV

OK, this is tough because it brings up past stupidity on my part, but....
I drive an '82SC Targa, 160,000 km, mine since 130,000 km in 2001. I have always managed 22-25 mpg in town and 29-34 hwy (Imperial gallons, btw), but in late 2006 replaced plug wires and following errant Bentley manual ended up with incorrect firing order. No immediate harm apparent, since correction the car has performed well, pulls fine right to redline, but last summer thought my fuel economy wasn't right. Just went thru my first tank of 2008 and am getting 16-18 mpg combined city-hwy. Something isn't right.
No obvious leaks from tank, lines, etc running or stopped. No fuel smell. Oil temp stays at first white mark. I do not own an exhaust gas analyzer. I am due for a valve adjustment so will be visiting my mechanic but I want to canvass the forum for others' experiences (search not fruitful, except to confirm my current fuel economy is an outlier). For some reason I have a really bad feeling about this. Fortunately, my wrench is trustworthy.
It just seems so dumb to book the valve adjust, and say "By the way, my toy rocket just doesn't get the gas mileage it used to." Truth is, despite recent price increases I'm more worried that I damaged the engine when I mixed up the plug wires.

2.7RACER

I would be inclined to check the injectors. I would at least run some Techron through the engine.
I'd check the obvious like air cleaner filter, Sparkplugs.
Your mechanic can do a few things as well if you tell him about your poor mileage.

ron mcatee

Stan, +1 for injectors. My mileage went south 17-19 mpg) and when I checked the injectors, 2 were OK, 2 were dripping raw gas, 2 had erratic spray patterns. After I had them cleaned and flowed on the bench, I now get between 27 & 28 mpg on the road.

Good luck.

StanV

Thanks for the advice, this is something I can do before taking the car in. Have to work today though, so it'll have to wait.

Mike Murphy

Something to consider is to check how you are driving your car. Are you more confident now than when you use to drive? If you drive even a little more spirited or leave it in a lower gear, that will have a big effect on gas mileage.

Also, are you driving any faster on the highway? I was getting 25mpg when I first bought my car, but couldn't manage anything higher than 19 on the highway. I finally found that it was the difference between 70 and 85mph.

Did you change tires recently? Do you have the correct pressures?

Are your brakes grabbing? After a long drive (not spirited, just highway), go around your car and feel each wheel and see if they are warm. Brake pad grabbing will keep those suckers warm and kill your mileage.

Finally, if you are really worried about it and you want to sleep better at night, why not ask the mechanic to do a compression or leak-down test while performing the valve adjustment? Since the valve covers will be off and he's already in there, the cost should be minimal.

I don't think you did any damage to your engine. But since you were messing with the distributor, I would verify that your timing is correct. Also check the tensions on your belts. Belts can make a big difference too.

StanV

Thanks Murphyslaw,
Tires 3 years old, good pressures (35 rear, 29 front), I know I'm not riding the brake but I will take it for a long jaunt at speed and see if there are any 'hot wheels'; certainly nothing pulls to one side, but you never know and it's an easy test.
Different driving is a tough one to answer; in town I do tend to shift at higher rpm's than I used to, that's why I didn't worry about economy till I had done a long highway trip, mostly at 110-120 km/h.
We'll see.
If nothing else, these things make me more knowledgeable about the car, and make me appreciate it more.

theiceman

don't worry about the Bentley issue .. it could have ended in a whole lot worse situation ..lol