Poor Accelleration - 740

UK spec 1989 740 GL Estate. 2.0ltr Auto fuel injected. Pre Lambda Sond
model with std (not catalytic) exhaust. 123,000 miles and always regularly
serviced by Volvo.

The car was never particularly good on accelleration, it used to do 0-60mph
in about 12.5 seconds. The car has done only about 15k miles in the last 4
years and as my Son now has as his daily driver this is the first I have
driven for the last 2 1/2 years.

The car feels very sluggish on acceleration but cruises along fine once the
speed is up. 0 - 60 mph acceleration now a dismal 17 1/2 seconds
(previously 12 1/2) so something is up.

Accelerate away from stop using the throttle gently (i.e. normal traffic
speed acceleration) and the car appears fine. Put your boot on the gas
pedel and the car hardly seems to acceletate any quicker. Engine revs ok
(once it gets up there).

The engine had the cylinder head gasket replaced at 119k miles by Volvo
which cures the water coolant loss but this according to Son did not make
any difference to acceleration pre/post gasket change.

Car starts fine, ticks over fine and generally goes well enough. Aparently
the car has lacked acceleration for quite some time now. Brakes do not
appear to be binding - at least the disks do not seem to run hot when you
put your hand by them after a run. Hand brake is not sticking on. The air
filter is due for a change, has done 10k miles but it's not that mucky. No
Lambda Sond or cat on this car (just before they were fitted in the UK.
Fuel consumption has not changed and still does about 23 mpg around town and
25/6mpg (English) out of town which it has always done. Oil consumption is
negligible.

When accelerating it feels as if either the engine is not getting enough
fuel (the fuel filter was replaced at 100k) or it is being choked by not
enough air going through the air filter. Removing the air filter does not
appear to make a difference.

Could we be talking a sluggish fuel pump. I seem to recall that the older
740's had 2 fuel pumps, could it be one of these failing that is now
starving the engine of petrol. How can I check?

I really am open for ideas. I am totally stumped at the moment.

Many thanks

Andy

 

My first question (not knowning the specifics of this car) is what
fuel is being used (octane rating)? If it has the anti knock sensor
tied into the comouter, my first idea is that a low-octane fuel will
cause excessive pinging upon acceleration which will retard the timing
quite a bit.

If it can run at a high RPM (like near red line in any gear) for any
length of time then it should accelerate at low motor speed decently.
Try a tank of good fuel.

__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"

 

Another of my many "long shot, but easy to check" ideas that occasionally
pan out... with the engine warm, put your hand on the top of the air cleaner
box (where the filter is). It should feel barely warmer than the outside
temperature. If it has a fever, the wax pellet that controls the intake heat
has failed - common enough - and the hot air is taking its toll on the
performance. Check it anyway, because I'm told that sort of failure is hard
on the expensive AMM.

Mike

 

You're right about it killing AMMs, though in this case he doesn't have one.
Since the car is pre-lambda it has K-jet mechanical injection, something
that went away here after '81 except in the 240 Turbos.

 

Its an auto yes? Is the kickdown working fine, and more-over when it does
kickdown are you reaching 'full' revs before it selects the next gear? Not
familiar with the B200F but think it ought to be in the region of
5000-5200rpm.

Secondly, with an assistant in the car pressing the pedal to the floor, with
the trunking off, check you are actually getting full throttle. The number
of times i've seen a stretched or mal-adjusted cable...

Tim..

 

This may be a long shot but a 740 I had, had problems with the ignition
amplifier (located behind the air filter)causing a weak spark, finally it
gave up on the motorway. just a thought. - Roy

 

HOW about giving the car a bit of stick now and again .In the lower gears
rev it out a little Volvos love a rev out .Why tune a sluggish car with out
cleaning it out with a rev through the gears .example on a open road lower
the gears and let it rev .Has the exhaust fouled up mine did on an old V6
wouldn't perform ,removed the muffler and it went well .Solution new muffler
and more revs as my wife was driving it gently ,all ways over the limit but
calmly ,where as I drive just a tad under the limit but use the box as a
manual and rev it out of occasion .

 

This weekend Me, Ricky (Son) and a techi are going to give Lola a good
seeing to. Before then we are going to have it MOT's as this needs doing
anyway by 3 Oct to see if this throws anything up. Have taken on board all
suggestions here and other forums and will work through. Inshalla, we will
actually be able to pin point what is causing the problem but I would settle
for it just working ok again.

Will give feedback when we have something to tell.

Bye the way have already tried the 'thrashing the bollocks off it trick'.
To no avail. The car has always been driven sensibly with a bit of stick
but not screwing it. My wife certainly never hung around in it when she was
the principal driver and neither do the kids. I do know what you are
getting at though. Did the same on an mid 60's Austin 1100. Belonged to an
old lady who never exceeded 45 mph. Held it down in second and gradually
increased the revs then 3rd until it went from prob a max 3 to 3.5k rmp to 5
to 6k rmp and was fairly screaming. Did this for a 50 mile journey and
together with a replacement air filter (theirs was VERY shitty - unlike
ours) did the bizzo. The elderly lady thought we were miracle workers.

Andy