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- Technical Q & A (https://www.subaru-svx.net/forum/forumdisplay.php?f=5)

- - EGR (https://www.subaru-svx.net/forum/showthread.php?t=60526)

Quote:

Originally Posted by Lookin4SVX (Post 711819)

Could you explain to me how the EGR sensors tells the ECU something is wrong?
I figured it was a matter of ohms on the line, like most other sensors.
So I was thinking just replace the line from the sensor with a hot wire of how ever many ohms is the normal reading.

There is no sarcasm in that question. I honestly want to know why it is not possible.

The EGR solenoid is operated by a duty cycle signal. The ECU will detect an open or shorted wiring, and a armature that is not responding to the ECUs signal (stuck or jammed.).

Quote:

Originally Posted by 1986nate (Post 711828)

You've got that backwards, a 92 ECU can go into a 92 Cali/94+federal car without a problem. It will never look for the temp sensor. If you put a 92 cali or 94+federal ECU into a Federal 92 car, it will throw a code because there is no EGR temp sensor or wiring. IIRC, the 92 Cali/94+Fed ECU's only need to see the temp sensor is plugged in and existent. It doesn't actually readily monitor the temps. (This may be different for OBD2 versions)

The EGR temp sensor is mounted on the passage that carries the exhaust gas from the exhaust manifold to the inlet manifold. When the ECU signals that the EGR opens, it looks for the rise in temp at that sensor, that confirms that gas is passing to the inlet.
The problem is when the passages in the EGR pipe, and the inlet manifold passages, get blocked with carbon, no gas passes, no rise in temp, gives a code.
So to fix the 56 problem, fit a new solenoid. To fix the 34 problem, clean all the inlet manifold passages of carbon.

Harvey.

Bump.

I am getting my car inspected this week. I don't need emissions testing, though. Will I still pass even though I'm throwing a CEL for the EGR? The CEL will not come on unless the engine is warm. It's a '92. The last time I got it inspected, it passed, but I'm 2 hours away from that garage... If it won't, to my knowledge the 92's only throw a code for a dirty sensor, not the temp. sensor (correct me if I'm wrong), so I was wondering what the easiest way to clean it would be. I have a can of seafoam in my trunk, ready for business.

Quote:

Originally Posted by B 4 You (Post 716420)

There are two 1/8" ID vac lines on top of the throttle bodies - the one on the driver's side goes through the EGR solenoid. If you disconnect the hose from the nipple (and cover the nipple with something) and put it in the seafoam can, then run the engine, I think it would flow through the solenoid. Or it might only flow through when the solenoid opens and I'm not sure when it does so. Give it a try and see if it pulls anything out of the can. Actually better to try it with only a little bit of fluid first, in case more goes through than expected, don't want to flood the engine or anything. If it doesn't pull any fluid through, post back up and I'll figure out a way to make the solenoid open (the circuit is pretty simple).

I'll probably just fill a shot glass with the seafoam in order to not overfill it. Do you have a picture of exactly which hose that is? And are you saying that if the solenoid doesn't open it won't create any vacuum pressure at all? I've had people tell me that they did this procedure and it cleaned all that carbon buildup that's throwing that damn code.

Quote:

Originally Posted by B 4 You (Post 716429)

I don't know if there will be enough vacuum without the solenoid, gotta try it and find out. I don't have a picture, but there are only 2 of the small vac lines on top of the throttle body (have to remove the engine cover to get to them of course), and it's the one on the driver's side. Should be easy enough to find.

Quote:

Originally Posted by B 4 You (Post 716439)

Is this the right one?

yep. ..........

Remove the hose from the nipple . You say cover it with something? The something like a hose or a plug. Put it in the can? Do you mean the hose you took off or the thing you put over the nipple
.?

Quote:

Originally Posted by Conn SVX (Post 716456)

Remove the hose from the nipple . You say cover it with something? The something like a hose or a plug. Put it in the can? Do you mean the hose you took off or the thing you put over the nipple
.?

Cover it meaning the nipple, so there's no vac leak. You put the hose in the can. I'm going to try this later on my car to make sure it's safe before I recommend you try it.

Thanks. I am Willing to try it. May clear my code.

Quote:

Originally Posted by oab_au (Post 711843)

It's information like this that I copy and paste into my svx reference document. Thanks, Harvey!

Quote:

Originally Posted by icingdeath88 (Post 711818)

There are tons of ways to do that. One of those ways is to switch to a 92 ECU. One way is to have a working solenoid plugged in and blocked off, so it can't ever get dirty/stuck again, and block off all the rest of the EGR.

https://dl.dropbox.com/u/37735806/EGR.png

inb4 "meme used wrong blah blah blah"

But in all seriousness, if I could that would be cool. My friend removed his from his Talon TSI to squeeze out that extra ounce of boost haha.

Quote:

Originally Posted by EdWindows (Post 716528)

Yes When I took off my intake manifold and replaced all the brittle vac lines I removed the egr I blocked off the open hole in the intake manifold and plugged off the tube coming from the exhaust manifold, could not get the tube out of the header.
I kept the solenoid plugged into the wiring harness under the manifold.

Quote:

Originally Posted by 92 SVX (Post 716554)

I did the same with the intake manifold of my built engine, since it hopefully won't ever have a stock ECU attached to it. I hope you looped a vac line to connect the two nipples; I'd worry about dust and crap getting in there eventually and stopping it from working. Might also be a good idea to relocate the solenoid to somewhere not so hot, so it doesn't fail because the actual solenoid goes bad from the heat after however many years.

The 92 ECU can tell whether the solenoid is connected, and somehow it can tell whether it's stuck or not (probably detects a different current or something??). Like Harvey said, the later ones have a temperature sensor on the intake manifold right where the EGR connects, that the ECU uses to monitor whether the EGR is actually working or not, by detecting the increase in temp when the hotter exhaust gas is flowing past the sensor. If one were to measure the resistance at the different temperatures, one might be able to use a resistor to trick the ECU...

The 92s have a (14mm head) plug where the temp sensor is on the later ones. AFAIK, the 94s don't actually throw a code when the EGR system isn't working though. It will throw a code if the temp sensor is missing, however, which I know because I have a 92 engine in my 94, and if I use the 94 ECU it throws a code (code # 34). Not sure about the Cali spec cars, or the OBD2 cars, but I bet they'll throw codes for a missing temp sensor, a stuck or missing solenoid, and the the EGR not functioning. There are 3 codes: 34, 55, and 56. I think the 92s can only throw 34, because they have no temp sensor, and therefore no way to tell whether the EGR is functioning or not, only whether the solenoid is functioning.

If you want to delete the EGR (on a 92), the most difficult part will be getting the line from the pass. side exhaust manifold out. Once you do that, you can just put in a bolt to plug the hole. I tried and I tried, but I could not get that fitting to loosen. Still haven't quite figured out how to solve that problem. Gene, what did you do?

There's not that much (if any) performance to be gained from removing it though, to be honest. Most EGR systems only open at high vac, and RPMs well above idle, which is basically just when you're cruising. At low vac, high loads, it should stay closed. Recirculating the inert exhaust gas instead of fresh air just reduces the amount of fuel that needs to be injected, which ought to improve mpgs very slightly. I see two main benefits from tossing it: cleaner engine bay, and cleaner engine. The exhaust gas is disgusting, and if you ever look inside port where it goes into the intake manifold, you will cry from how nasty it is.

It also gets rid of a tiny bit of the more toxic by-products of combustion, which I guess it a good thing, but the way it does it is kind of stupid. It lowers the combustion temperature. NOx are formed when O2 and N2 are burned together at very high temps. I guess by diluting the air/fuel mixture with the CO2, H2O and other inert combustion products, it lowers the combustion temp enough to prevent that. Yea, when you burn hydrocarbons, you get CO2, CO, and water. You can think of an EGR as a really retarded water-injection system if it makes you feel better. :lol:

Ed, stop using memes wrong. This isn't Facebook, lol

Quote:

Originally Posted by icingdeath88 (Post 716557)

If you want to delete the EGR, the most difficult part will be getting the line from the pass. side exhaust manifold out. Once you do that, you can just put in a bolt to plug the hole. I tried and I tried, but I could not get that fitting to loosen. Still haven't quite figured out how to solve that problem. Gene, what did you do?

Did you try using this?

http://ecx.images-amazon.com/images/...500_AA300_.jpg

Combined with a crow's foot wrench, it might do the trick.

EDIT: Sorry if the images are annoying. I'm bored with text. :P