Tuesday, 29 December 2009

EGR Valve

I have some time off work for the week as I do every year at Christmas time, and I quite enjoy the mandatory holiday. I had a great Christmas; it wasn't as hectic as I had imagined despite the conglomeration of relatives at my parents house on Christmas Day, and having Michelle's parents stay with us for a few days after that. On the hypoglycemia front the holidays have been a great boon; I feel better. Today I decided to attempt to check the EGR valve in the car: I figured it might be an all-day job, and I was right--between looking after Kate and playing online games and reading a John Grisham novel, it took all day...

EGR stands for Exhaust Recirculation Valve. No vehicle really needs one to run; however they're good for the environment, and since our Mazda 626 recently failed AirCare, I decided this should be the next thing to check. (It failed on NOx levels only. A mechanic checked our engine codes and found a code 6. There is no code 6. Therefore I was back to square 1. I got the oxygen sensor changed. The car seemed to run better for a day but still failed Aircare. Then a day or two later the muffler developed a hole...argh!) What the EGR valve does is recirculate engine exhaust back into the engine to be re-burned. But if it is clogged or one of the numerous sensors or circuits related to it malfunctions, the EGR valve is rendered useless. I parked the car outside on the street where I had decent daylight to work by, opened my Haynes manual, and set to work.

After a few hours I had managed to remove the air intake housing stuff that was in the way of getting to the offending machinery; identify the valve itself although it was different than the manual described, and I had loosened one of the two bolts that I could feel below. I couldn't see what I was doing half the time, as the part is behind the exhaust manifold and sort of below it as well. This sort of work is hard on the back of the knees! I took a break for lunch and then resumed my toils. I borrowed a small ratchet from an unsuspecting shop to make my travailing easier, and it moved mountains (my apologies for waxing poetic). Victory! I took the EGR valve upstairs to clean it.

There was a little bit of carbon in the holes but nothing that would indicate clogging. I soaked it in WD-40 and wiped what I could with a rag. I checked into the price of a new part and when I heard it was $306 I decided I had better put this one back in and test it later with a vacuum pump--if it's toast I can get a 'new' one at Pick a Part! So I put it back in the car before it got dark, and believe it or not the car started right back up!

Now, for the million dollar question: if cleaning this valve actually fixes my NOx, can I use foil tape to fix the hole in the muffler?

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