Volvo manuals say the EGR for a car with manual transmission is part #6842726 and for the automatic transmission cars the part is #6842725.
Anybody knows what the difference is?

I can't really see why they should differ depending on type of transmission.

mila

Hi Mila,

The EGR valve available placed the EGR temp sensor in the EGR valve.

The prior NLA version did not have an EGR temp sensor mount option. That sensor required that the EGR tube between the EGR valve out to the intake manifold house the EGR system temperature sensor.

You plug the EGR tube between valve and new EGR valve, and install the EGR temp sesnor in the hole at the side of the newer EGR valve. It may be old EGR design has been replaced by newer if Pierburg makes it to this day.

EGR temperature sensor fits into the smaller threaded hole, downstream of the valve inside the EGR valve body. Maybe to be more accurate when sensing the EGR valve opening and the exhaust gas heat.

Check the first EGR tube between the manifold out to the EGR valve body inlet. This tube can rust and clog.



Prior post on EGR:

https://www.brickboard.com/RWD/volvo/1650110/740/760/780/egr_valve_delete_substitute_piping_parts.html

The EGR sensor usually fails at the strain reliefe for the two diurable black wire right at the sensor.

Shows EGR on my 1991 240 and I want to rid the car of it and swap in LH-Jet 3.1 for 240.
https://brickboard.com/RWD/volvo/1668538/740/760/780/egr_sensor.html

Some of the made by Volvo EGR diagrams are wrong. QA correct version:

https://www.brickboard.com/RWD/volvo/1650152/740/760/780/egr_valve_delete_substitute_piping_parts.html





If you do not need to suffer emissions inspections, EGR is removable. You need to remove EGR piping, plug two holes, and replace the ignition control and fuel control ECUs to the equivelent no EGR versions. Verify pinouts at ECU connectoir but I believe pinouts for a fuel or ignition system version (LH-2.4, EZK116, you may have Motronic).

EGR east about 1 MPG reducing your fuel economy.

If you have PulsAIR also removal is more problematic.

Hope that helps.
--
Trollin' MacDud. Professional technical writer, editor, illustrator and former Volvo mechanic at TWO repair facilities in two different states with three university diplomas I earned and paid for myself. Only car I ever owned is the Volvo 240 starting in 1984. All with manual gear box. Wee. Brickboard is fun. ha.

Teeeeeeeeeerrrrrrooooooooooooooooooooooooolllllllll

I didn't realize there were different EGR valves, so I got curious and did a bit of reading for you. Yes, for vacuum controlled EGR valves (the type used in our B230 engines) there are commonly different valves used with automatic and manual transmissions in all makes. The difference in design appears it may just be the diameter of internal porting.

It's done for the sake of minimizing emissions during normal driving conditions. The valves are opened and closed using engine vacuum, which of course varies with engine load. Most references I saw make note that compared to a manual transmission, automatics place a slightly different load on the engine at idle and during acceleraton and deceleration. The EGR valves are designed to respond differently to open and close more similarly under the slightly different vacuum conditions.

So that now begs the question of why don't turbos and NA engines also use different EGRs? The engines do have very different vacuum profiles over the rpm range, with turbos having a vacuum pump. It may well be as Grey245 suggests having a lot to do with your foot staying on the gas in addition to engine loading.

The 6842769 EGRs for manual trans appear to be more readily available from sources. Based on my reading, although it may affect gas mileage a little bit, the difference in performance between using one type of EGR valve over the other should be minimal. If anything, I would expect using a possibly slightly less responsive EGR designed for a manual might make for slightly improved performance in an automatic at the expense of a little gas mileage. However, because the later ECUs monitor EGR operation through a temp sensor and are able to electrically control when vacuum is getting to the EGR then any effect may be extrememly subtle.

I found an old thread here on the brickboard that you may find interesting Hacking the EGR System. The KittyG replies are especially well done with great pics and info.

For more general information on EGR principles of operation, here's a mildy interesting technical article I found on the Hella website Exhaust Gas Recirculation
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

That's awesome information.

Once upon a time, I ran into a newer EGR temp sensor and ECU being about 8x as expensive as the old type. Do you happen to know which one is NTC and which is PTC? NTC is when the resistance drops as the temperature increases, PTC is both increasing together. Each mounts into a different spot - newer goes into the valve, older goes into the tube.

Wow, thanks Dave!
Very educational indeed. I thought maybe the different part numbers were due to some different plumbing connectors attached to the valve itself.
But as you explain it certainly makes sense.
Oddly enough the valve for manual transmissions is almost impossible to find new
here in Sweden, despite manual transmission cars being far more common.
The auto tranny valve is readily available.

Well, my valve wasn't closing properly so i wanted to replace it. When I couldn't find a new one I soaked it in caustic soda and cleaned it and the pipe to the inlet instead.

mila

Dear Mila,

Hope you're well. I, too, found Dave's analysis to be insightful and so helpful!!

Several years ago, Pierburg stopped making this EGR Valve, which thus became "NLA" ("No Longer Available" in Volvoese). The part was used in 240s, 740s, 940s, etc.

Wherever automatic transmissions were most common, that part (#6842725) vanished. Wherever stick-shift transmissions were most common, part #6842726 became scarce.

There may be aftermarket versions.

Hope this helps.

Stay well!!

Yours faithfully,

Spook

Everytime you shift gears in a manual, you do something you wouldn't in an automatic: lift your foot off the throttle. I couldn't think of any other reason as they appear to be identical from the outside.

Those part numbers are superseded: 6842725 = 3517849 and 6482726 = 3517848.