save me from running around....

....in circles.

The 240 suddenly began running somewaht poorly. It had previously been
running a slight bit rough (I was suspecting dirty injectors, but had
no evidence to indicate that this was the problem), but it was
starting easily, and getting good mileage and had good power. Ran like
that one day, next startup had erratic idle and very poor
low-rpm/off-idle performance, hesitation and lack of power at off-idle
transition of throttle opening. Mid to upper end runs well. No OBD
fault codes (socket 2 and 6).

The idle was a bit high, then seemed to settle in, but it is still not
acting quite normal. I checked the IAC (slowly 'crushed' the air hose
and engine stopped). The Throttle Position switch is functioning
normally (checked with ohm meter), I cleaned the contacts of the AMM,
and wiped the interior of the throttle boidy as best I could without
removing it (don't have a replacement gasket right now). I
disconnected the vac line that goes into the interior and plugged it-
no change. I checked under the hood for any obvious vac leaks (visual,
tactile, and auditory), but nothing obvious.

I will need to remove them all and check more closely, but I could
find no leaks in the air intake routing (like the IAC take-off from
the intake hose, loose clamps, etc.).

I have Plugs, wires, cap and rotor that should heve been here today,
but not until Tuesday now... :-(

I had done no work on the car or made any changes to precipitate this.

I am thinking that it might be:

- dirty throttle valve
- dirty injectors
- vac leak (but where?)
- sticky or mis-functioning IAC valve

I don't think it is a fuel delivery problem as that usually will show
at high loads and high RPMs (starvation) and not at low RPMs. I hear
the pump start up when the key is turned to POS2, and the car starts
right away, even when cold or when it has been sitting.

So I still have some investigating to do, but thought that these
symptoms might help someone point me to an obvious place and save me
some time...

TIA!


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

 

[ ... ]

Does your engine have a vacuum advance on the distributor? If so, try
disconnecting it. The diaphram in the module may have broken.


Gary

 

Thanks for the response, Gary. No, it is a '90 and only uses the
distributor to distribute the coil's output, with timing and advance
computer controlled.

I have a Mityvac device on the way (should have bought one 20 years
ago). Just about every car I have ever owned has had the vac advance
diaphragm fail and I would have checked that right off.


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

 

_____
What is an IAC valve? Idle control motor/valve?

1) Pull throttle body, clean (with lacquer thinner), and reinstall. I
can usually reuse the green gasket. Sometimes i make a new one from a
sheet of bulk gasket stock. May need to get a new butterfly shaft seal
that sits on shaft opposite idle control switch. Is available from
Volvo dealer only as far as i know. While you have the throttle body on
the bench, you may consider applying the improvement listed in the
following URL: http://www3.bc.sympatico.ca/Volvo_Books/maint3.html.

2) Poor AMM contacts usually cause the car to go into "limp mode", and
you will know that for sure because the engine won't rev over 3,000 rpm
and have little power. Cleaning AMM contacts is always a good policy
and i do this at a 6 month interval.

3) Check that the idle control motor is actually working. It should hum
with engine idling. Use the old "screwdriver handle to the ear" trick
to act as a stethoscope. Pull the idle control motor, and clean it
thoroughly. I recall that both devices on my 1989 sedan were filthy
about 3 years ago. The engine idled perfectly afterward. With Mobil-1
motor oil, the amount of deposits will decrease. I also put an
insulating sleeve on the rubber hose from the PCV valve to the throttle
body to reduce buildup of sludge.

4) I assume that you replaced the plastic fire screen in the PCV tube,
and that you cleaned the small orifice in the brass vacuum fitting on
the manifold? By the way, i liked your description of "measuring" the
vacuum in the engine using a chunk of oil coated plexi-glass on top of
the oil filler opening.

I use an old metal oil filler cap into which i soldered a short length
of 1/4 inch copper tube. Then i get about two feet of clear tygon PVC
hose, and slip that over the copper tube. Next, i make a U-shape with
one foot of the hose on the other end, and hold it on a paint stirring
stick with two elastic bands. Now i have a make shift U-tube manometer.
After adding some water to about half way in the U-tube, i can measure
vacuum in inches of water when i attach the oil filler cap to the
running engine. You can hang the manometer on a piece of wire on the
hood. The vacuum you will see should be somewhere between 0.2 to 0.5
inches of water. There is no danger of sucking water into the engine.

5) The injectors rarely need cleaning. In the 10 years i have run the
240 sedan, i have never noticed a problem.

6) The O2 sensor should be ok, as no codes were set. When that sensor
fails, the engine will run in another "limp mode" with an extremely rich
mixture. I have replaced the sensor twice in 10 years. Next time i
will buy a generic Bosch one, not a Volvo brand as they cost too much.

7) I can't remember if the 1989/1990 models have a vacuum line to the
ignition computer or the ECU. The 1986 model has a line to the ignition
computer mounted next to the window washer fluid reservoir. Perhaps
someone else cares to comment on the presence or absence of vacuum
advance on 1989/1990+ years of 240 Volvos ?

/ JCH

 

Yes...

More details- I am getting a 121 error- bad signal to/from Air Mass
Meter. I visually examined the wires at the connector at the AMM
(pulled back the boot) and they seem ok, but will investigate further.
I have messed with it a few times, clered the code, but it keeps
posting it. I am currently looking for a used AMM to see if that is
indeed the problem.

Here's the odd thing- the Bentley manual states that the "Check
Engine" light should illuminate for an AMM fault, but the lamp does
not illuminate. The lamp IS illuminated when the key is in PII with
engine off though, so I know the lamp is good.

I did that this morning. Removed throttle body, removed the the
postion switch and cleaned the body and blew it out with compressed
air. Is running a bit smoother now, but as mentioned aboe, still
getting error from AMM.

I also adjusted the throttle cable, and the stop (idle) screw on the
throttle body as per the manual.

Too late, but it is bookmarked and will be considered.

I did clean those up, and they look shiney, and the car has good
top-end power- just a bit weak and hesitant off-idle until about
1500-2000 RPM, as a guestimate. Easily runs over 3000 RPM without
difficulty.

When disconnected the motor immediately quits, so I assume that it is
working... Is that a correct assumption?

I will be pulling the Idle Control Motor for a cleaning tomorrow.

I did check and clean the flame trap a couple of weeks ago, and it was
not that bad. I will check all the manifold fittings as well.

Mine is showing vacuum at the cap (holds the cap on with a little
suction force when it is loosened).

I have an old mercury carb synchronizer for the BMW I can use.

Nice to know. But with California gas being what it has been... I do
run only quality, nam-brand gas in it.

With all that done it is better, but not right yet.

Thanks for the reply and I will post to the thread as I get further.