My 1994 Lexus has a rather sudden and dramatic drop in MPG.

Asked by Mar 14, 2013 at 11:00 AM about the 1994 Lexus LS 400 Base

Question type: Maintenance & Repair

I've had this car for 9 years, and during this time I've always gotten 19 to 20 miles per gallon. In recent months it dropped to 14 MPG and was running rough. My driving habits have not changed at all. I've had the following work done:
Full tune up ($800)
Replaced 02 sensor
Replaced mass flow meter
Replaced timing belt and water pump
Since then, my MPG has actually gotten WORSE. It's down to about 10 MPG.
It has 158,000 miles on it and has been a great car. One thing I notice is that when I start it up in the morning, there is a very strong smell of gas around the car.
Fuel pump? Thermostat problem? Any ideas? I love this car but am running out of money to put into it.

2 Answers

92,325

Gas smell would point to a fuel problem. Have the fuel regulator checked. The regulator has a diaphragm. The engine vacuum pulls on it and the excess pressure is sent back to the tank. If the diaphragm ruptures, raw gas is sent into the air intake and fuel pressure at the injector nozzle increases. Both conditions result in a very rich mixture and decreased MPG's. --- Usually on a older vehicle the O2 sensor response slows down and signals more fuel than necessary at the injectors. Since you replaced the O2 sensor, that can't be it. -- I repeat, have it checked and tested before replacing to make sure it is the cause.

1 out of 1 people think this is helpful.

Many thanks! I'll have it checked out.

Your Answer

Add photo

Related Questions

LS 400

Looking for a Used LS 400 in your area?

CarGurus has 246 nationwide LS 400 listings starting at $2,950.

ZIP:

Search Lexus LS 400 Questions

UK Questions

Are you a UK consumer? CarGurus now has a discussion forum in the UK.

Lexus LS 400 Experts

#1 Tom Demyan
Tom Demyan
Reputation 410
#2 FordNut
FordNut
Reputation 350
#3 dandyoun
dandyoun
Reputation 210
View All

Related Models For Sale

Used Lexus GS 300
41 Great Deals out of 920 listings starting at $3,168
Used Lexus ES 300
17 Great Deals out of 1,078 listings starting at $150
Used BMW 7 Series
177 Great Deals out of 5,719 listings starting at $3,299
Used BMW 3 Series
1,565 Great Deals out of 39,014 listings starting at $1,200
Used Lexus SC 400
71 listings
Used Toyota Camry
1,214 Great Deals out of 97,665 listings starting at $1,250
Used BMW 5 Series
633 Great Deals out of 15,459 listings starting at $2,495

Used Cars For Sale

1999 Lexus LS 400 Base For Sale
31 listings starting at $2,950
1997 Lexus LS 400 Base For Sale
10 listings starting at $2,995