Really bad MPG

[TC 1997]

hi, i have a 97 TC with 243K really strong silent engine. I have put a K&N air and oil filter, mobil one engine, tranny, and rear diff fluids. use conoco and shell gas, sometimes use fuel injector cleaner and still get like 11-12 mpg. can anyone help.

[olopezm]

When was the last time you replaced plugs and wires? Fuel filter would be a good idea too. I would check for vacuum leaks, take a look at the PCV tube and to the vacuum distribution tree at the firewall.

Oscar.

[TC 1997]

i replaced the pugs and wires alittle under a year ago and i have also replaced the fuel filter twice. i have never checked the for vacuum leaks, I will try that.

[olopezm]

Get rid of those Bosch plugs/wires and any other parts, most of the times have beed reported as bad.

Install a set of motorcraft/ autolite plugs and motorcraft wires, might sound more expensive but you are already spending more money with low MPG's. Check fuel pressure as advised in the other thread too, but I don't think it's your problem...

Oscar.

[olopezm]

Forgot to mention that copper plugs have been reported to work the best, single platinum have worked for some people and doubles or iridium are said to be a waste of money as you'll get no gain in these engines.

[TC 1997]

i figured i should just stick to the stock parts but im dumb and listen to what people say on tv. also the owner befor me i think had installed amps in the trunk and screwed them down and i think they screwed them all the way thru to the fuel tank the inside of the car sometimes smelled like gas thats how come i guessed they screwed all the way thru.

[olopezm]

A faiure in the EVAP system can cause a fuel smell after you turn the car off, even when the computer has DTC's for it, sometimes it won't show any nor the CEL will be on.

Check the nylon hoses that run from the vent solenoid, located near the windshield at the passenger side, to the intake and the charcoal canister. These can crack or become obstructed. That would also cause low MPG's and the fuel smell of course.

[TC 1997]

Ill try that and let you know

would it be a good idea to replace the canister?

thanks.

[Blue)(Fusion]

Remove the Bosch parts. Replace with OEM Motorcraft O2 sensors. I got mine from Tasca Parts Online for under $35/each (far less than dealer).

Which cat was replaced? It's recommended to replace them with the OEM cats unless you are replacing them on both banks at once. The differential pressures between the left and right banks due to different cats can cause performance/efficiency loss.

Use Motorcraft or Autolite spark plugs only. Single platinums gapped to .054" are recommended. They will last 80-100k in normal conditions. Be sure to actually check the gap of them!!! Pre-gapped are not always correct....in fact I've found it to be a 50/50 chance it's gapped properly.

Other basic fuel efficiency tips:

• Clean MAF with MAF (or electrical contact) cleaner
• Check vacuum pressure is atleast 19-20 in. Hg. (inches of Mercury)
• Check for proper fuel pressure at the fuel rail
• Get rid of K&N filters. Stick to Motorcraft FL-820S oil filter and appropriate Motorcraft air filter. These filter smaller particles and still flow more than the engine is capable of at maximum RPM (stock)
• Replace compromised fuel tank/EVAP canister/lines from the previous owner's amp installation. Fuel evaporating and escaping into your trunk/cabin is not only wasting money but also is EXTREMELY DANGEROUS.
• Check for proper tire inflation (I use 38-41psi to reduce rolling resistance, but ride comfort suffers slightly....tire wears differently this way, so YMMV)
• Don't drive offensively

[All2kool]

Originally Posted by TC 1997

hi, i have a 97 TC with 243K really strong silent engine. I have put a K&N air and oil filter, mobil one engine, tranny, and rear diff fluids. use conoco and shell gas, sometimes use fuel injector cleaner and still get like 11-12 mpg. can anyone help.

Your MPG will vary depending on how you drive. These cars will coast for miles. Try this: Next time you are driving and you see the light ahead turn red, take your foot off the gas. Your LTC will coast without loosing much speed for 1/4 mile or more.

Drive your LTC as if you're running on fumes and your MPG will improve.