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Your '89 740 B230F is LH2.4. The Check Engine light with a 1-1-3 code on the diagnositic connector says there's a "fuel trim" issue. The ECU is unable to adjust fuel mix (injector pulses) and timing (advance) to keep combustion within the pre-programmed limits for O2 oxygen sensor exhaust readings. Although it could be faulty injectors, the problem is much more likely elsewhere until you have further condemnation that it's the injectors.
When you say it starts like a tractor, that immediately makes me think of a blown exhaust manifold gasket or worse still a cracked manifold or bust downpipe connection. That could definitely upset the O2 reading and exhaust manifold expansion can dramatically change the leaks once the engine gets hot. Start by thoroughly checking the entire exhaust side for puffy noises and leaks, first when cold then when hot. Use a stethoscope technique if needed, such as listening through tubes and down metal rods to help isolate noises.
You describe intermittent long periods of fairly normal operation followed by periods of very abnormal operation. That part doesn't add up to it being just an exhaust leak unless the tractor noise comes and goes at the same time. Things may well be temperature sensitive, so always think electrical when that happens.
My wild guess at this moment beyond a blown exhaust manifold gasket would be the ignition side, with a badly worn distributor cap/rotor that sometimes gets in the way, possibly bad ignition wire connections or a failing ignition coil that overheats. When was the last time the ignition was checked and attended to? On the fuel starvation side, I'm wondering about a seizing main fuel pump. Is the fuel pump red hot to the touch underneath when this happens? Any chance this only happens with a 1/3rd tank of fuel or less?
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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