Uncle joe_1991_240,

If removing the EGR piping and plugging up the EGR holes on the intake and exhaust port, please keep in mind Goofy Cally State vehicle emission testing stations may also perform a visual inspection.

The fault codes on the 700-900 FAQ (https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm) does include the fault codes on sockets two and six for the EZK module.

Your big blue Bentley Volvo 240 service manual bible, or the Haynes (best the 1997 and final imprint), or the Volvo factory service manual all list both code sets.

You may read of individuals, in articles and thread on this brickboard, that relocate to Goofy Cally State with their Volvo, and they replaced the catalytic converter with a 49-state catalytic converter (not acceptable in Goofy Cally, so you fail the inspection, and if the catalytic converter cost does not exceed the maximum repair charge before you are forgiven, those may have to replace the 49-state with a 50-state for Goofy Cally State.

Intake and exhaust port on fuel inject engines is the same as intake and exhaust manifold in carbed engines.

EGR was not entirely integrated into the fuel and ignition management in the Bosch LH-jet 2.4 and corresponding EZK ignition module. The EGR function is more adjunct and not integral to the system, yet the OBD-1 codes remain, the the check engine light remains illuminated.

Woops, you are in Iowa. No worries, I believe.

So go ahead and plug up.

Depending on the 1991 240 mileage and whether the engine has seen synthetic engine oil or regular dino mineral oil, the EGR piping can becomes clogged starting at the end where the EGR pipe, downstream of the big EGR vacuum controlled valve and back up over time. Like atherosclerosis of the EGR piping of the heavier exhaust hydrocarbons condensing inside the EGR piping. (A similar action to what clogs the PCV valve - you should inspect this system, also.)

(I also have a 1991 240 with EGR that Germany required then. That 1991 Volvo 240 of mine comes from Germany.)

A clogged PCV pipe at the end may be clogged around the EGR temperature sensor. So, when the EGR valve opens, allowing hot exhaust vapor, under pressure, into the intake port and engine, and the EZK ignition module expects a temperature range. Such a fault throws a fault code that illuminates the check engine light.

Verify EGR valve function. The EGR valve vacuum diagram can fail, closing the EGR valve.

Or, worse, the EGR vacuum valve gets stuck open, dumping hot exhaust into the intake port at all times and that's no good to your B230 Volvo engine.

So, first, clean the EGR piping.

Another step, as you are in Iowa, is to replace the Bosch LH-Jetronic 2.4 ECU with EGR and the Bosch EzK ignition ECU with a non-EGR 2.4 modules. You may or may not have to reposition conduction terminal points where they connect to both modules. I believe the EGR function is adjunct and can be removed without losing plug and play with a non EGR LH/EZK 2.4 modules.

Yet verify with schematics and diagrams the position, find these modules at a yunkard or ePray (eBay), and you may plug the EGR gas outlet on the exhaust port or merely replace the exhaust manifold with a non EGR manifold in the same year range like 1990-1993. (CAREFUL and WATCH them exhaust port studs on the light aluminum alloy cylinder head).

EGR exists to better burn oxides of nitrogen. The EGR system, without air injection into the exhaust port, reduces fuel economy on your 1991 240 by about 1 MPG or so.

Should you keep the EGR, your primary concern is the ERG-vacuum controlled valve and the first EGR pipe from the exhaust port out put to the EGR valve input. While made of stainless, that valve loses the stainless, can rust, and fail at the most inconvenient moments.

I have redundant EGR parts for my 1991 240 sedan, with manual transmission and moon-roof, yet I want to convert the whole engine control system to the more sprightly Bosch LH-Jetronic 3.1 and corresponding EZK ignition, wire hanress, and exhaust manifold swap.

Also wanna get rid of the cold start injectors, too, someday.

Questions, comments, kitties, holiday treat recipes, and compliant of no more Saturday morning cartoons?

cheers,

Egg Nog Season Boyeeeeeeeeeeeeeeeeeeeeeeeeeeeeee.