Re-adjusted the throttle switch to 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:
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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?
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.
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.
On Wed, 06 Oct 2004 02:39:11 GMT, the illustrious radietz favored us with the following prose:
Wow, that's a terrific detailed checklist of what I need to do! I shall start going through it on Monday and see what results.
Some observations:
My "airflow sensor plate" frequently has oil on it. Pretty much whenever I open the airbox I start by removing the rubber cowling and cleaning the oil out of the venturi. Not lots of oil but enough to make it dirty. This is what has caused me to suspect that the other end of that leg of the system (which I believe is at the throttle plate) may also be gummed-up.
In an earlier discussion (Re: My volvo tried to kill me) Mike F pointed out:
"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."
How does this information affect your advice re: the throttle switch? My "microswitch" has three terminals of which only two have ever been connected and the third always open (I'm assuming it's the NC terminal).
I'm planning (dreaming) to change my valve-cover gasket this weekend (the new gasket has been travelling around in my trunk for 3 months). Would this be a good time to take a look at the valves and see that they are properly adjusted? Anything else I should be looking at while the cover is off?
I'm not sure I understand this correctly: "hose between the pre-pump and the sender unit outlet pipe" As I understand it the Fuel Pressure Sending Unit is in the hanger under the car shared with the Fuel Pump. Is this hose a short one from the pump to the FPSU or from the in-tank pump?
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