The Check Engine Light illuminated on my 1993 Volvo 940 Wagon yesterday and remains on but not flashing. The OBD II code indicated a 2-4-1 code "EGR System flow too low". The engine runs fine and does not exhibit any symptoms associated with this code, (e.g. uneven idling. stalling, hard to start, excessive fuel consumption, high exhaust NOx, etc.) Has anyone else experienced this anomaly? Should I remove, clean or replace the EGR valve? I have not done this job before, is it difficult? Is it okay to still use the car given that it runs fine?

Any advice will be greatly appreciated.

Many thanks,

OnlyVolvo

One more thing I forgot, and this should probably be the first thing to check, is blockage in the EGR tube connected to the intake manifold. If it gets grungy with caked oil vapours at the top then that would restrict flow and throw that 2-4-1 code. If the throttle body throat and plate is often found to be dirty then definitely suspect this.

If you disconnect the top of the tube you may not be able to move it back enough for inspection and cleaning without also loosening the EGR. Simplest thing is to remove the throttle body and try to use a flashlight and mirror followed by a stiff piece of wire to ream it out. Failing that, disconnect the EGR tube at the top so you can get into a bit better. The lower end of that EGR tube is often thoroughly frozen onto the EGR valve so you may have to loosen the EGR mounting on the block if you need to push it back a bit more. After three goes of penetrating oil and leaving it overnight, I still couldn't get that lower fitting loose -many have reported similar.

If you need to remove the EGR itself, the triple fitting on the main EGR pipe is also extremely difficult to loosen, but that one usually eventually lets go with enough penetrating oil, a bit of heat, letting it soak overnight, rinse and repeat, then use the biggest wrench you can get on it while squeezing in your hands against a counterhold wrench. Some combination wrenches are a bit too long to get in there and be able to turn them. I used a large Crescent wrench as the counterhold. Stupid thing is you have to remove the EGR valve to get at the oil separator box that's mounted behind it, which is why I was doing this. Many people simply resort to leaving the vertical tube connected to the EGR valve and if needed to remove it on the bench using heat.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

Interesting notes on the 940 EGR setup.

After dealing with EGR headaches with the 850, I switched over to full synthetic
and switched again when I got back into red block engines. The full synthetic has been cleaning out all the mess from dyno oil and the interval between clear oil, and ugly blackremains of it's former life surviving on 1993 grade oil have been increasing with each oil change.
Do you feel that 940 EGR problems are aggravated by dyno oil, and feel like I do that Full Synthetic oil is way better for all auto engines?

Dyno oil pricing by the quart is more money than using Wally world full synthetic by the 5 quart jug, so now it's not a big price thing to upgrade to FS Oil.

Bill

The cheapest synthetic is likely better than the decent dyno oils, so would presumably help with vapour deposits in the intake system as well as combustion deposits. Wally's Auto Mart is also where I get my oil these days. The only thing different I can think of is going for a High Mileage semi-synthetic formulation that contains seal conditioners, which for me means trying to postpone changing the weeping engine rear main seal for as long as I can (the front seals can easily be done at T-belt change time). You can always buy seal conditioners as an additive and add a little bit to the synthetic. I'm sure half of what they recommend would be adequate. Extra seal conditioner will swell the seals even more, but that can also increase wear on the seals.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Just a few random ideas for you:

There's an EGR pipe off the exhaust manifold that goes around behind the block to the EGR valve. Awkward to get at and see, but clean up and carefully inspect for a crack, corrosion or weak spot in that pipe, especially in or just after the first bend as it goes behind the block from the manifold. That EGR pipe is unfortunately NLA, so welding in a section of SS tubing might be needed.

Spray the EGR valve shaft with some PB Blaster and try working it back and forth a bit if you can.

Check the connector and vacuum tube on the EGR valve. With a piece of vinyl tubing, sucking on the EGR vacuum should visibly move the diaphragm.

The EGR vacuum solenoid up high by the power steering reservoir isn't known for failures, but if it did then that could cause your problem. Make sure everything's connected and clean. I don't have time to check, but I recall that there's a component test (DTC 2? or maybe 3?) that you can do at the diagnostic connector to exercise that valve. Check the 700/900 FAQ here (if you can get through, arggh) under Engine-OBD for that procedure. It's extremely subtle to detect movement of the solenoid during that test, so passing that test is good, but failing that test doesn't mean it's bad.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now