Hi Rattlebone54,

Is your Volvo suspension so stiff it rattles your bones?

Nyuk! Har-har-ha-heh. Okay maybe not so funny.

Not Turbo in that 1991 Volvo 740. Normally aspired, yes? I'm not fluent in all OvLov configurations that may include EGR.

Also, all of the posts I list may provide a start to your strategy.

No such thing as Santa Rosa, Colorado. You used to reside in NorCally?

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

Though this table is wholly incomplete. It does not list the probable ignition ECU(s) that comes installed, mated, as it were, to the fuel injection ECU.

Please provide the Bosch / Volvo part number on the LH-Jetronic ECU. I'll guess you have the EGR-enabled:

0 280 000-933

or

0 280 000-946

The 700/900 ECU/AMM Reference Chart, incomplete as it is, lists the -933 as used with Turbo 700-900. The -933 I have I pulled from a non-Turbo 700 or 900, maybe 1991 or 1992.

I have a yellow label 0 280 000-556 from the factory for the 1991 240 with EGR and seized left front Bilstein HD (Billy HD sucks, btw, as they seize on other makes as water intrudes and freeze and the beark at the valve body). That 1991 240 has the 0 280 000-946 in there with the original ERG-enabled EZK116 ECU.

About the only part you may be able to find as new old stock is the vacuum controlled EGR valve. I believe the temperature sensor is also still available. Please read through the linked posts. The newer EGR valves, if you read them linkedin posts, install into the EGR valve body downstream of the actual valve.

There exists a cap nut, I guess, the part number can be found in them linked posts, to plug the second EGR pipe between the EGR valve output to the intake manifold.

The longest of the two EGR pipes that secures at the back side of exhaust manifold is NLA. Made of stainless, yet the stainless, I guess nickel (not chromium stainless) loses the stainless and begins to rust from the exhaust manifold end forward and can fracture there. You may be able to find spares at a salvage yard or online at eBay or who knows.

You can try by getting out your multimeter and check whether or not the vacuum servo, the cylinder thing with vacuum and electrical connection with white cap, receives power. Also, as Phil Machine Man repeatedly stated in many posts that there is a foam air filter under that white cap. If you read the posts or use the search feature to find Phil Machine Man's posts, he indicates that you carefully prise up the white cap, and remove the now old and collapsed foam with maybe some durable fiber material to pack in there that can take under hood conditions.

The filter is there as when the EGR control from the ignition control module de-powers that servo, the vacuum on the EGR valve is released closing the valve. So, I guess to filter out particles in the event, if momentarily, on vacuum enable or disable, the engine does not suck in particles.

Finally, with some spare gasket material, you may want to perform the EGR service. Volvo listed the service as 15k miles on K-Jet models and extended that to 40k miles? I guess? I forget now.

The service was to inspect and qualify proper EGR function. So, vacuum, when the EGR vacuum solenoid is powered as the engine coolant reaches minimum temp through the ignition ECU connection to the ECT,

The service can include an inspection of the second EGR pipe for exhaust vapor condensation. If this clogs, as it can if using dino oil, infrequent changes, short intown trips, and such, the exhaust flow diminishes through the EGR and so the EGR temp sensor encounters a flow that does not match the preset values in both ECUs. So, check the OBD socket six. Repeat until no new codes display.

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The causes are not so many with a vacuum gauge and voltmeter you cannot find the cause and remedy it.

Or, if I read the wiring diagrams right, though verify if you have to move wires to different connector pin positions, install a known good LH-Jet 2.4 "0 280 000-951" or Turbo non-EGR ECU and a known good non-EGR EZK ignition ECU.

And then plug the exhaust manifold with the flanged bung and washer (?) and plug, cover, fabricate a heavy aluminum or steel cap with holes for the two screws where the second EGR pipe terminate at the using gasket material appropriate for the application.

Does that restatement help? Again, look at the linked threads, Use the search feature to find out more.

Hard yet not impossible to find non-ethanol gasoline where I am in the toilet city with the arches and baseball cardinals. Yet corrupt Iowa and other ethanol producing states sure love them ethanol subsidies. Uses considerable carbon based power generation to process vegetative matter to make ethanol.

Human-induced climate catastrophe. What elocutionary without resolution. Like Brexit.
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