My Volvo is no longer trying to kill me but...

Re-adjusted the throttle switch to <CLICK> just as the throttle opens
and closes and this has not caused the engine to race so one
adjustment made, one possible problem eliminated, no problems solved.

I would like to next disassemble the throttle body to see that it is
clean and clear of any build-up. I have occasionally found oil in the
air filter box and once in the pipe leading to the air intake
manifold. By 'throttle body' I mean the area underneath the round
metal puck with 'Turbo' written on it at the terminus of the
air-intake pipe at the top of the engine, held down by 3 bolts. I
believe that under there I will find my throttle plate.

Having a Turbo makes all the documentation and diagrams I can find
just a bit inaccurate. I'm currently working with the following
diagram:

http://www.vlvworld.com/photo_pieces/kjet.jpg

I'm also hoping this course of investigation will lead me to make
sense out of the following observations:

(NOTE: By HOT I mean engine stopped and sitting for 1-2 hours and by
WARM I mean engine stopped and sitting 2-4 hours. COLD > 4 hrs.)

Engine Weather Result
~~~~~~ ~~~~~~~ ~~~~~~
Cold Cold Starts well, idles too fast
Hot (sits 1hr) Cold Starts/runs great
Warm (sits 2+hr) Cold Starts with difficulty

Cold Warm Starts well, won't idle w/o throttle
Hot (sits 1hr) Warm Starts/runs great
Warm Warm Starts with difficulty, erratic idle

Also, why would it be that tapping the gas pedal when idling has the
exact opposite effect one might expect i.e. revs drop before rising
instead of just rising? Could it be that the throttle is allowing gas
to enter but the the air is just late by that tiny little bit leading
to a moment of lean mixture and, therefore, hesitation?

Also, is there anything I can check on the cold start valve?

 

And, as always, thanks for all your advice and taking the time to read
my long-winded posts.

blurp

 

OOOPS... And I forgot I was starting a new thread so the car is a 1983
240 Turbo with k-jetronic injection system and 330K km.

 

As always with any running/starting problem on a K-jet you have to find
someone who can test the fuel pressures. And then take the time to check
the fuel flow from the in-tank pump.

From what you've stated and given the mileage on the car I would suspect
the following given that the tune up parts, valve adjustment, and hoses
(air in this case) are are in good serviceable condition:

The constant idle motor depends on proper wiring at the throttle switch,
an accurate coolant temperature signal, and proper adjustment of the
throttle plate. Back probe the three wires on the back of the idle motor
with a test light clipped to ground. You'll find that probing one wire
causes the idle to raise to maximum (2200-2400 rpm), the center wire
does nothing, and the third wire causes the motor to close completely.
If grounding the close signal wire does nothing either the throttle
plate is open too far, the throttle switch is not working, or the motor
itself is stuck/gummed up or otherwise not behaving correctly. The other
two possibilities can be addressed visually. Clean the throttle housing
and adjust the throttle plate. See if the throttle switch clicks when
you crack the throttle. There is also a blue-white wire that terminates
in a blue test connector along the right front fender. Clipping a test
lead between it and ground holds the idle motor shut while the engine is
running and allows the throttle plate to be adjusted to something like
750-850 rpm. Ungrounding the wire should let the idle rise to 900-
950rpm.

I suspect the control pressure regulator is not working. Control
pressure is likely too high--above 3.7 bar (engine warm). This will
cause erratic high idle because the mixture is too lean, also diminished
performance when hot. There is also a vacuum check valve in the plumbing
on the bottom side of the CPR that allows for enrichment on acceleration
when cold. When malfunctioning this causes the car to fall on its face
after one rapid acceleration, I.e. a hard run up in first gear leads to
NO power when second gear is engaged. The engine will continue running
however. If you pull over and stop to see why the engine fell out, raise
the hood, verify that it's still there, slam the hood shut and get back
in the car you will find that it operates normally. The thermal ported
vacuum switch that control enrichment has now closed and the CPR has
switched to warm running operation.

Hard starts are often caused by the deteriorated hose between the pre-
pump and the sender unit outlet pipe. Very hard starts with prolonged
cranking can often be the result of a leaking diaphragm in the fuel
pressure accumulator. Extra very hard prolonged cranking to start can be
a failure of the frequency valve, which is extremely rare.

A K-jet without leaking injector seals is impossible to find. Replace
the seals (upper and lower) and the stands they go into. If you can find
someone who has one, have the injectors put on a Bosch injector
tester/cleaner. Try to get a uniform spray pattern when flushing at full
pressure, get the injector to chatter when just barely applying enough
pressure to get the pintle to lift.

The was a service bulletin that used a pulse relay to energize the cold
start valve after a period of 10 seconds of cranking. Someone may still
have a copy that would show the part numbers and instructions for
installing it.

Another maintenance item that should be address is to clean the airflow
sensor plate. Goop builds up on the top and causes weird throttle
response issues.

HTH.

Bob

 

I'm having pretty much the exact same symptoms with my 87 740 turbo.
When I start from cold weather+cold engine, it'll barely idle at first.
Dropping it into gear makes it splutter, then stall. Tapping my foot on
the accelerator at the point just makes it stall faster sometimes.

Thanks for your reply Bob