If you are certain the timing belt is at or beyond 50k miles of service, time for a replacement. Continental / ContiTech is Volvo OEM quality (or was as China Geely owning Volvo now).

Arm chair root cause analysis is sort of hard in this guess fest, to use Art's accurate phrase, so, some general tips on what to look for.

Timing Belt

If the timing belt was the cause, the belt may slip a tooth on a crank or one of the two cam timing gears. The slip, of skip, may prevent engine start, or the engine would run so terribly as to not be operable safely.


OBD-1 Test Box

You are in the corrosion belt of Queens NY as I am in the toilet of St. Louis, MO. If you have continuity through the wire harness the issue may be corrosion at the OBD box on the backside of the left side inner fender.

https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

Read through: Can't Obtain an OBD Code? Malfunctioning OBD Code Reader?

A wiggle can do wonders. Yet you have the all clear 1-1-1 in OBD socket 2 (fuel) and OBD socket 6 (ignition) engine control.


Battery and Fuses

The battery cable lugs are secure to the battery? The cabling at the rear of the alternator are secure? Use a nut driver to tighten that hardware. You own a electric multimeter? Can you test for volts at the battery on a cold start (around 14.5 VDC) or as is warmed up (around 13.8 VDC).

The battery does not reset itself on it's own timeline. You are working with an electromechanical system. Root cause analysis though the intersecting subsystems make for a paradox at times when finding root cause.

You use the lightest of key chains. RWD drive Volvo ignition key locks and ignition switches want a light key chain. If you hang dozens of other keys and tools on it, that can cause problems in both the ignition key lock and switch. Become practiced with not locking yourself out of house and home, however.

You do know to spin the fuses in the fuse box? What about the oft-mention 1990 and older LH-Jetronic engine BAY ATC fuse. Corrosion can form there. Here is Art's write up from his clean flame trap site that does not offer a TOC after all these years.

http://cleanflametrap.com/emfuse.html

Corrosion can form at any bonded contact. Like the back side of the fuse box.


Power to Fuel Pump(s). Fuel Level in Tank Corresponding to 'Bucking?

Also, Art, who posts here in your thread, provide guidance as to testing the fuel pumps. You should hear both run. Someone here made mention of the intank, pre, or transfer pump. At 1/2 or less full fuel tank, if original factory install intank prepump and send, a small fuel line section deteriorates and the prepump out put returns to the tank, so the main, or inline, pump, loses priming. More so on turns or if going up hill or down hill(?). I forget inclination or declination.

Does a full or nearly empty gas tank change this behavior?

You do not describe the nature of this bucking? Do you know engine bogging, where the engine is at idle, and warm or cold you depress the gas pedal and it bucks and seems to want to stall yet does not go until moving at 25-25 MPH? Could be the throttle position switch. These can fail do to intrusion of engine bay grime or wear, and the failure threshold in the Bosch engine control won't report it in fault codes.

How many miles? Auto or manual transmission?


Electrics and Sensors?

I'd guess fest the cause sounds like an intermittent electrical issue. Check the fuel injector relay. Swap in with a known good relay. Parts like these in the trunk and on the shelf are useful.

Also, there is the engine crankshaft position sensor (CPS) at the back of the engine. Has this been replaced that you know of? An inspection of the sheathing, and if split, may suggest fault there. Should be replaced by now. Sort of doubt it as failure here is a no-start or stalling condition with engine shutdown. A code is set in socket six.

Engine Bay Environment

Engine belly pan installed? If not, though the failure may result in an engine fire, the B+ circuit between the alternator, starter motor (not the solenoid), and the battery + post routes behind the crank pulley. With oil and grime or an otherwise filthy engine bay, insulation can fail. I doubt the cause.

EGR?
A broken EGR pipe at what end? Near the manifold connection end or at the EGR valve?

Failed EGR piping results in one or more EGR faults usually in socket 6 as EGR is monitored by and controlled by the Bosch EZK116 ignition ECU.

The loud exhaust note itself suggest you have exhaust leaks elsewhere? There is a nut to plug the hole in the exhaust where the EGR pipe would secure.

I'm unsure, yet NY-state emissions control inspection is as bad as CA-state.

EGR piping usually clogs from the intake port manifold end backwards. Eventually, a fault code is set as exhaust gasses do not pass through the system when the engine is warmed up.

So, I'm gonna guess you cleared the codes or you have faulty power connection to the ECU maybe through the in engine bay engine management fuse. In a 30-year old 240, that fuse and fuse holder assembly should have been replaced by now with something better, as Art recommends in this aforementioned link to Art's cleanflametrap site.

http://cleanflametrap.com/emfuse.html


What am I on About? Brake Fluid?

Finally, I have to ask, what is the brake fluid color in the brake fluid reservoir? Better not be black or seized brake calipers are the result. Use a Motive brand pressure power bleeder. Though regular inspection of the braking system helps.

Questions?

Hope that helps.

Unemployed Technical Writer
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