why am i getting hummer gas mileage?!?

[aquaman2g]

I'm hoping you can help me out with a gas mileage question. I have a 87 lesabre that's been sitting for the last three years.I just started runnin it again and i'm only getting about 10 miles to the gallon. The car runs smooth at high speeds(under acceleration) but shakes heavily while maintaining speed. I switch out sparkplugs, air and fuel filters, pcv valve and have poured in sea foam and other gas station fuel injector cleaners. What else should i do to improve gas mileage? I was expecting 17-20 from my v6. Is this to much to expect from an 87 lesabre?

[2turboimports]

Is the check engine light on?
Did you also change the spark plug wires?
Did you check out the distributor?
Did you check the ignition timing?

[aquaman2g]

Thanks for the reply. I did change the wires with the spark plugs. I couldn't reach one of the plugs so i still have one old one in with the five new ones. I don't know what to look for about the ignition time or the distributor. Are these things that i could/should adjust? The service engine light does come on after a few mins. of driving. any suggestions are welcome. This is my only car and it's costing me about 10-15 bucks a day to drive(completely killing my pockets!!)

[beef_bourito]

if you have a distributor you should check the points and see if they're still good, if they're worn they wont fire when they're supposed to and you wont have as much power or fuel economy. you could probably get some new points at your local canadian tire or autozone.

as for timing, you'll need a timing light, i don't know where you could get one, you might be able to borrow/rent one from autozone or a friend. also does black smoke come out of your exhaust? if it does you're probably running rich and should have that checked out. if you run rich you're engine is dumping too much fuel for the oxygen in your engine to burn so you get worse fuel economy and worse power. for that you'll probably need to take it to a mechanic.

[MagicRat]

Originally Posted by beef_bourito

if you have a distributor you should check the points and see if they're still good, if they're worn they wont fire when they're supposed to and you wont have as much power or fuel economy. you could probably get some new points at your local canadian tire or autozone.

as for timing, you'll need a timing light, i don't know where you could get one, you might be able to borrow/rent one from autozone or a friend. also does black smoke come out of your exhaust? if it does you're probably running rich and should have that checked out. if you run rich you're engine is dumping too much fuel for the oxygen in your engine to burn so you get worse fuel economy and worse power. for that you'll probably need to take it to a mechanic.

These engines have no distributor. They use coil packs and magnetic crankshaft position sensors for timing, so no adjustment is possible.

Lets assume the plug wires are routed correctly, (it can't hurt to check again)

The coil packs usually come in a set of three, where each coil fires 2 cylinders. These coils are controlled by an electronic module, which is attached to the coil packs.

If one coil in the pack has failed, (or the module has failed) the engine is only running on 4 cyl and will function EXACTLY as you describe.

IMO this may be the reason why this car was parked 3 years ago.
Replace the coil pack and the module together, if you can get a good used set from a wrecking yard.
If you have to buy a new one, try the module first. If the problem persists, get a new coil pack.

Also, install a new oxygen sensor. These usually have a service life of 50,000 miles, but are often neglected.
Also, change that last plug. You may need to get a swivel for your socket wrench, or a small extension, but it should not be difficult to do.
What about your air filter? Is it dirty?
Finally, 20+ mpg is what this engine should get.

[wazza4678]

also check the fuel pressure regulator operation...diaphram can dry & crank when left for long periods of time..this is a simple & inexpensive test