My Volvo tried to kill me

Well it's not really as bad as all that. The car is 1983 240 Turbo
automatic.

I did some work over the weekend trying to diagnse and repair a few
persistent problems. I have been having trouble with my cruise control
not working so, following the troubleshooting guide I received from
Grtdane, I checked all the electrical components (all checked out) and
reconnected the wires to the governor. I checked the Throttle Actuator
hoses (one thin and one fat with a cable running to the throttle body)
and found the thin one did produce vacuum (as required) but the fat
one wasn't airtight (a-HA!). I wondered where it goes and how to
replace it?

Then I set to work on figuring out why my car won't idle until it's
warm and why it stalls if I'm really gentle on the gas (that is, if
I'm coasting slowly and I give it just enough gas to raise the tach a
few RPM and then release it the car stalls). The last time this
happened I had loose air-hose clamps and tightening them and cleaning
the air filter did the trick. Not this time.

Then, looking at my Haynes Manual I saw that the Throttle Sensor
(which is a small flat box with a copper tab sticking out and resting
against the throttle). According to Haynes when the throttle opens
there should be an audible 'click' as the copper switch also opens.
This has never been the case so I bent the copper tab until it clicked
on and off as the throttle left the "zero position".

Then I went for a drive. I live downtown in a crowded city.

Several times when accellerating sharply the pedal would take off! The
car would accellerate wildly and the pedal would pull away from my
foot. Braking had no effect on the throttle and yielded the expected
"one foot on gas one foot on brake" results. Only kicking down HARD on
the gas pedal would free it from this spell. One time I had to kill
the ignition because it started racing right before a stop sign. I was
able to reproduce the problem whenever I stepped hard on the
accellerator.

Disconnecting the cruise governor did not solve this problem.

I bent the copper tab on the Throttle Sensor back so that there would
be no more clicking but, although the problem is gone, I just don't
think that was it. What was happening was definitely vacuum at work on
the gas pedal so I'm suspecting the Throttle Actuator is a factor but
don't understand how a leak can cause MORE vacuum. Should I disconnect
the throttle actuator? Could it be the Sensor? I suspect vacuum is at
the root of all my problems (cruise/idling/racing)... any ideas on
what to check next?

Thanks in advance.
blurp

ps. sorry this mesage is so long, I wanted to get all the details in.

 

The mechanic! Don't trust your life in someone who doesn't know what
they are doing like your are now!!!

 

I would check your motor mounts, as if they are broken the engine will
torque to the side and put the accelerator cable on a bind and pull it to
WOT . This has happened to me on a 240 and the fix was new motor mounts.


Harold

 

Good one Mrs. Fricker.

Anyhoo, upon closer inspection it became apparent to me that the
plastic threaded barrel adjuster through which the cable from the
Throttle Actuator passes was broken and folding at 90 degrees to the
piece through which it passes. Make sense? I figure when the throttle
was applied sharply it caused the cable and housing to back off from
the threaded retaining clip and fold over, effectively pulling the
cable and applying gas via the actuator cable regardless of the actual
position of the gas pedal. Stomping the gas pedal would then return it
to its correct position. It has been straightened out but I should
probably find a replacement for the threaded plastic barrel.

Next question...does that vacuum-powered throttle actuator do anything
outside its cruise control duties? Can I safely disconnect the whole
thing?

Also, I was reading up on the throttle sensor and I suspect someting
is up with it. The manual shows it as a small part about the size of a
box of matches (which it is) and that it should have 3 connectors on
top (which it has). This is where things go astray:

1) Haynes says it's supposed to 'click' as the throttle is opened from
a zero position but that was not the case before and it's not now that
I set it back. With the throttle at zero you can reach in with your
finger and push the switch a bit further and it will click but under
normal operation it never gets pushed far enough to click.

2) There are three electrical connectors on the part but only two
wires have ever been connected to the thing, the third terminal left
unused.

3) Haynes says that a 4.something current should be detected across
two of the terminals at idle and then drop to zero as the throttle
opens up (of course that's where it's supposed to 'click'). With mine
just the opposite is true. I may have this backwards since it's been a
few days but, regardless, whatever Haynes says my readings were the
opposite. This leads me to believe that Haynes may not be taking into
consideration variances due to age and model. I figure a
malfunctioning part would give diminished readings but not the exact
opposite.

Am I wasting my time even looking at this thing? Could it really have
any role in the idling/cruise/racing issue being explored here?

Thanks again,
blurp
ps. WOT = Wide Open Throttle?

 

As an additional note:

The item I've been referring to erroneously as 'throttle sensor' is, I
believe, actually a 'throttle switch'. I have been completely unable
to locate any picture of a part that resembles the part I'm taking
about (!!!) but the part I'm talking about DOES NOT look anything like
this:

http://www.vlvworld.com/VolvoRepairManual/repair_pics/throttleswitch.jpg

Although it's clearly the part in the above picture that the Haynes
manual is referring to. I don't have any part under the hood that
looks exactly like that.

Furthermore I have looked at over 500 images on the Brickboard and
cannot find one that shows engine compartment contents identical to
mine! None show the Throttle Actuator (next to the fuel filter in my
car) and all have a very different throttle connection on the engine
(mine is a tall cylinder with layers that move independantly of each
other depending on which of 3 cables pull on it).

I'll post a picture soon.

blurp

 

240 Turbos (and other Volvos of that vintage) have a microswitch for a
throttle switch. All it's designed to do is signal the idle computer
that the engine is at idle. This particular part is actually a standard
electronic component, a double throw, single pole switch. Some have the
switch closed at idle (use the common (C) and normally open (NO)
terminals) and others have the switch open at idle (use the common (C)
and normally closed (NC) terminals). The switch should click as you
have a transition to and from the idle stop position.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

As I suspected! So it is unlikely that a modification to this switch
to enable that click at "transition to and from idle stop position"
could have caused the engine racing. I will, therefore, bend it back
to once again operate in this way with some confidence that the engine
won't be taking off on me.

Thanks,
blurp.

ps. Re: The leaking fatter vacuum hose running to the throttle
actuator... When parked with the engine running I can hear a whistling
(vacuum leak) if I race the engine up above 3K RPM. Is this likely to
be the same leak or is there another leak I should be tracking down?
In other words, what is that fat vacuum hose actually conneced to?
(The people who publish manuals with wiring diagrams would do well to
publish the vacuum schematic as well!)

 

Have you checked to see if you won a Darwin Award for this?

( http://darwinawards.com/ )

 

Darwins are awarded to those who die in pursuit of foolish deeds.

I'm still alive.

Maybe tomorrow... watch the list!

blurp

 

Keep in mind that maybe the "modification" was done to "solve" or hide
the problem you're now dealing with.

The fatter hose from the vacuum actuator goes to the brake and clutch
pedal switches. This way not only is the cruise control switched off
electrically, the vacuum is dumped as well so it loses its "muscle".
Disconnect the cable from the actuator to the throttle pulley to make
sure this is not the problem.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)