What's causing poor 740 gas mileage?

BrickBoard Archives

The files contained in this listing have been automatically archived from the active forums. Because the vast majority of posts are now in one place, this archive is considered legacy. You should use the SEARCH feature OR choose your topic and select date tabs within the forum you choose.

What's causing poor 740 gas mileage?[850/1995] posted by Rob Abel on
Thursday, 26 March 1998, at 10:12 p.m.

'87 740 with B230F with 115k. Bought the vehicle with 113k so don't really
have a frame of reference as to expected performance. I DO know that it
doesn't get near the gas mileage as my '93 940 (B230F w/ 80K) which gets, in the
city, 20-24 mpg.

The '87 is getting more like 15-16 mpg. It was blackening plugs a bit, but
I went to 91 octane and driving in city with OD off, and that seems to have
helped the plug situation. Car starts instantly and seems to run OK (some
vibration at idle in drive, but again I'm not sure what's normal).
Exhaust isn't restricted. Any ideas before I break down and take it to a
local expert and spend my hard earned $$?

The basics have been taken care of (cap, rotor, throttle body cleaned, 8-pin
connectors cleaned, pcv system cleaned, new air and fuel filters.)

Re: What's causing poor 740 gas mileage?[850/1995] posted by Leon Tong on
Friday, 27 March 1998, at 9:00 a.m.

Rob,

Check for a vacuum leak, specifically on the air-intake pipe between the air mass meter and the throttle body. The one on my 86 240 was cracked at the shoulder of the nipple connecting the pipe to the flame trap. This allowed unmetered air into the engine, and caused a 3-4 mpg drop in mileage.

Leon Tong

Re: What's causing poor 740 gas mileage?[850/1995] posted by Steve Seekins on
Friday, 27 March 1998, at 1:10 p.m.

Check your wiring harness carefully for deterioration - particularly under the intake manifold where the various sensors are located. Also check the engine temp sensor - if it is telling the engine that it is stone cold, the engine runs full rich all the time. Also, failed O2 sensor can cause very poor fuel mileage. Check at test lead with high quality dwell meter.

Volvo Club of America

Re: What's causing poor 740 gas mileage?[850/1995] posted by Roger Sundelin on
Saturday, 28 March 1998, at 4:37 p.m.

Howdy
When I took my 745 to the Bosch-service center with the same complaints,they
told me to look in the mirror.
Roger

Brickboard.com is not affiliated with nor sponsored by AB Volvo, Volvo Car Corporation, Volvo Cars of North America, Inc. or Ford Motor Company. Brickboard.com is a Volvo owner/enthusiast site, similar to a club, and does not intend to pose as an official Volvo site. The official Volvo site can be found here.