EGR Lift Sensor (Exhaust Gas Recirculation)

[watch4it]

Since the valve operates intermittently, I do not see losing 2" in 10 minutes as a leaking valve; a valve that starts losing vacuum immediately after applying vacuum is
a leaking one. And you said the hoses are damn tight, so no vacuum leaks from there anyway.

Can you take a good picture of the thermostat pipe where the temp sensor and the other two switches are screwed in? One of those is for the radiator fan, and the other tells the ECU engine temperature.

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<a href="http://s984.photobucket.com/albums/ae322/chokeyourchicken/?action=view&current=DCFN0001.jpg" target="_blank"><img src="http://i984.photobucket.com/albums/ae322/chokeyourchicken/DCFN0001.jpg" border="0" alt="Photobucket"></a>

Crap what type of link should i be selecting to let you have a link to my pics? The one I selected the one time posted my picture here on 3Gees. Didn't meen to do that.

here are my latest attempts for pics. Hose #12 and hose #19 come out of the green switch hose 12 goes to the vacuum switch on the themostate pipe hose #3 comes off the other side of that switch and goes to the charcol vapor cannestor mounted on the firewall. Hose #19 goes over to the valve on the front of the plenum on the injection and it has a little nylon adjustor lookin knob on the bottom of it and a vacuum pod in the top. Second picture. I checked the snap type connectores for the 2 switches as you asked and the seem clean and tight when ya snap them back on.
The switches on the thermostat pipe are 1. the vacuum switch with hose 12 running to it and hose 3 from it to the charcol canister. 2. The temp sender next to the vacuum switch. 3. The two switches on the top of the pipe.
All the vacuum hoses That I have messed with were like they were glued on, but they were not glued. I have checked them all and they all seem tight. The ones I took loose feel the same (tight) after I replaced them onto the connections.
Watch4it

[watch4it]

Since the valve operates intermittently, I do not see losing 2" in 10 minutes as a leaking valve; a valve that starts losing vacuum immediately after applying vacuum is
a leaking one. And you said the hoses are damn tight, so no vacuum leaks from there anyway.

Can you take a good picture of the thermostat pipe where the temp sensor and the other two switches are screwed in? One of those is for the radiator fan, and the other tells the ECU engine temperature.

and the other tells the ECU engine temperature.
So the one I changed and that had the loose connection was just for the gauge in the dash it wasn't the coolant temp sensor. It was the single wire switch next to the 2 hose vacuum switch.????

[watch4it]

Well I just went out and I don't know why I checked all the vacuum lines again while engine was up to op temp.
I found the click is coming from the orange colored solenoid next to the EGR solenoid. I unplugged the green solenoid (blk-yel) wire and that made no diff,so i unplugged the EGR selenoid and that made no diff, so I unplugged orange solenoid (blk-yel) wire and it made the click stop. When i unplugged the orange solenoid the click with rapping the throttle stopped. The hoses coming from the orange selenoid are 12 & 15. 15 goes to the vacuum addvance on the distributor and 12 is joined together with the other green selenoids 12 hose and it goes to the vacuum switch on the thermostat pipe.
I put my vacuum gage on the end of the canister that runs to the EGR Selenoid and as soon as I plugged the gauge on the engine stumbled and died. It would run fine with the hose just disconnected from the canister. It looked like It drew about 15-18"hg when I had the gauge hooked up. If i tied into the EGR solenoid hose and reved the engine it would give me about 8" hg and then that reading would drop back to zero. Rap it again and the vacuum would go about 8" and then drop again.
the other hose on the end of the cannister comes off at a ninety and it is the #16 hose to the EGR valve.
Don't know if any of this is relavant.

[Dr_Snooz]

If your air chamber started with three nipples and now has only two, then what happened to the third vacuum line?

[ecogabriel]

Well I just went out and I don't know why I checked all the vacuum lines again while engine was up to op temp.
I found the click is coming from the orange colored solenoid next to the EGR solenoid. I unplugged the green solenoid (blk-yel) wire and that made no diff,so i unplugged the EGR selenoid and that made no diff, so I unplugged orange solenoid (blk-yel) wire and it made the click stop. When i unplugged the orange solenoid the click with rapping the throttle stopped. The hoses coming from the orange selenoid are 12 & 15. 15 goes to the vacuum addvance on the distributor and 12 is joined together with the other green selenoids 12 hose and it goes to the vacuum switch on the thermostat pipe.
I put my vacuum gage on the end of the canister that runs to the EGR Selenoid and as soon as I plugged the gauge on the engine stumbled and died. It would run fine with the hose just disconnected from the canister. It looked like It drew about 15-18"hg when I had the gauge hooked up. If i tied into the EGR solenoid hose and reved the engine it would give me about 8" hg and then that reading would drop back to zero. Rap it again and the vacuum would go about 8" and then drop again.
the other hose on the end of the cannister comes off at a ninety and it is the #16 hose to the EGR valve.
Don't know if any of this is relavant.

First, when you plugged the hose going to the EGR solenoid with the vacuum gauge you acted AS IF the solenoid was acting the EGR system. Engine stumbled and died tells that there is enough vacuum to operate the system, that vacuum reachs the EGR valve, and that exhaust gases find their way to the intake manifold.
I think you tested the EGR solenoid earlier applying battery voltage to it; it should kill the engine when powered

It still surprises me that there are no code 12 and you have an emissions failure for NOx. If there were an electrical problem, the ECU should flag it. For instance, a non-working solenoid is flagged as code 12 because ECU operates EGR and when it compares EGR valve reading (from the valve's sensor at the top) it sees something different as it expected. Same if the valve sensor is the problem. Same if there were a vacuum leak or no vacuum in the system (which we know it is not the case here)

The only thing I can think of is that ECU does not operate EGR system because it thinks engine is still cold, and EGR system does not operate with engine cold. It is maybe anectodal, but my failed NOx values were FAR WORSE than yours -above 2K whatever the unit-.
I know from reading about emissions stuff that if the engine runs rich that cools down combustion chamber (it increases other emissions, but I'm thinking about NOx). The instance in which the engine runs richer is when it is cold. The only thing I am thinking about is that perhaps the temperature sensor is failing, not enough to flag a code but enough for the ECU to see engine as cold.

I would do this: I would unplug the EGR valve vacuum hose and start driving the car that way. If ECU sees engine hot then it would try to operate the EGR system and because of the unplugged hose it would not operate it, so it should post a code 12 and light the dashboard light. If this is the case, then we should start checking the wiring going from the solenoid to the ECU
ON the other hand, if it sees engine as cold it won't try to operate it and there should be no code.

I'll check this logic with my car tomorrow and see what happens.

[ecogabriel]

If your air chamber started with three nipples and now has only two, then what happened to the third vacuum line?

HIs air chamber (the one in the car) has always had three nipples; the one in the box he bought from the yard had two

No third line anymore for 88-89, so the air chamber is different. They used a different solenoid valve so they also got rid of hose #17 that provided atmospheric pressure to the EGR valve when not in use.

[watch4it]

If your air chamber started with three nipples and now has only two, then what happened to the third vacuum line?

http://i984.photobucket.com/albums/a...003_edited.jpg
I never changed the canister. The only part I changed was the CVC Valve out of the JY box to mine. Everything else is still the same parts minus the catylitic converter which I changed on the smog techs advice.

[ecogabriel]

http://i984.photobucket.com/albums/a...003_edited.jpg
I never changed the canister. The only part I changed was the CVC Valve out of the JY box to mine. Everything else is still the same parts minus the catylitic converter which I changed on the smog techs advice.

My canister looks exactly the same; even the black tape is the same...

[watch4it]

I would do this: I would unplug the EGR valve vacuum hose and start driving the car that way. If ECU sees engine hot then it would try to operate the EGR system and because of the unplugged hose it would not operate it, so it should post a code 12 and light the dashboard light. If this is the case, then we should start checking the wiring going from the solenoid to the ECU
ON the other hand, if it sees engine as cold it won't try to operate it and there should be no code.

Hope your not testing on your car. I shure don't want anyone else to have problems.
I did as you stated above and it turned my PGM-FI light back on in the dash panel and set or flashes a code 12 in the ECM.
watch4it

[ecogabriel]

Hope your not testing on your car. I shure don't want anyone else to have problems.
I did as you stated above and it turned my PGM-FI light back on in the dash panel and set or flashes a code 12 in the ECM.
watch4it

I would not tell anyone to do anything I would not do myself.
Yes, I did what I told you on my car. With my car dead cold, I disconnected EGR valve sensor, turned it on and started driving. No codes until engine got warm, then code 12. Turn engine off, then back on, and started driving; as the engine was already warm, the dashboard light came on almost immediately.
Later that day I did another test but this time with what I exactly told you (#16 hose disconnected). ENgine cold, I drove for a mile or so with no dashboard light but once it was warm... dashboard light on and code 12 on the ECU led.

So, whatever problem flagged a code 12 when you first posted seems gone now.
Your ECU does not flag a code when everything is connected because it is using your EGR system. I had thought that if the TW sensor was off range somehow it might not let ECU know that engine was warm enough for EGR to come on... well, I was wrong although the theory was right; you can drive the car while cold and no dasboard light (or computer code) would show up until engine is warm and attempts to use EGR system.

Now we have a failure that is EGR-related but your system -for all evidence we have- works. The only reason left is EGR passages partially or totally clogged. It may be that your EGR valve is clogged with carbon, or the individual runners to each cylinder are partially obstructed. Far less likely, the pipe bringing exhaust gases from the exhaust manifold to the EGR valve may be clogged. IN any case, even if the system works, if there is an obstruction somewhere that prevents exhaust gas to reach the cylinders you'll have a NOx failure in an emissions test.

You may try removing the EGR valve and looking for carbon deposits if you have not done so. With the valve out you may try running the car to see if exhaust gases get to the valve; you'll hear noises if the passage from the exhaust manifold is unobstructed. Oh, the f... nuts on the EGR valve are f... hard to get out; make sure you get a hexagonal socket of the right size or you may not be able to get them out

Try getting the document below; although it applies to Accords 1990 and later they have the same delivery system of individual EGR passages and suffer the same problems; what refers to the 1990 model in that document seems to square right with 3Gs.

http://home.comcast.net/~em-engineering/T2T013.pdf

Sorry for the delay: I was out of town last weekend and I am nuts w/school stuff...

[watch4it]

I would not tell anyone to do anything I would not do myself.
Yes, I did what I told you on my car. With my car dead cold, I disconnected EGR valve sensor, turned it on and started driving. No codes until engine got warm, then code 12. Turn engine off, then back on, and started driving; as the engine was already warm, the dashboard light came on almost immediately.
Later that day I did another test but this time with what I exactly told you (#16 hose disconnected). ENgine cold, I drove for a mile or so with no dashboard light but once it was warm... dashboard light on and code 12 on the ECU led.

So, whatever problem flagged a code 12 when you first posted seems gone now.
Your ECU does not flag a code when everything is connected because it is using your EGR system. I had thought that if the TW sensor was off range somehow it might not let ECU know that engine was warm enough for EGR to come on... well, I was wrong although the theory was right; you can drive the car while cold and no dasboard light (or computer code) would show up until engine is warm and attempts to use EGR system.

Now we have a failure that is EGR-related but your system -for all evidence we have- works. The only reason left is EGR passages partially or totally clogged. It may be that your EGR valve is clogged with carbon, or the individual runners to each cylinder are partially obstructed. Far less likely, the pipe bringing exhaust gases from the exhaust manifold to the EGR valve may be clogged. IN any case, even if the system works, if there is an obstruction somewhere that prevents exhaust gas to reach the cylinders you'll have a NOx failure in an emissions test.

You may try removing the EGR valve and looking for carbon deposits if you have not done so. With the valve out you may try running the car to see if exhaust gases get to the valve; you'll hear noises if the passage from the exhaust manifold is unobstructed. Oh, the f... nuts on the EGR valve are f... hard to get out; make sure you get a hexagonal socket of the right size or you may not be able to get them out

Try getting the document below; although it applies to Accords 1990 and later they have the same delivery system of individual EGR passages and suffer the same problems; what refers to the 1990 model in that document seems to square right with 3Gs.

http://home.comcast.net/~em-engineering/T2T013.pdf

Sorry for the delay: I was out of town last weekend and I am nuts w/school stuff...

Egr Nuts: First time I used a 12 or 13 mm 1/4" drive socket with a 1/4" 360 deg universal with a 1/4" to 3/8" adapter to a 3/8 drive ratchet and extension. Np, No wd 40 just a sharp smack on the ratchet when it was loaded with presshure and it poppedem loose, as the nuts loosened I raised the EGR valve with one hand as the nuts came to the end of the studs, the socket had a little dumb dumb in it to hold the nut. I can never find stuff when it drops.
Iam shure my passageways are clean I did that when I took the head off and the tube from the exhuast manifold was cleaned ot to. I will Pull the EGR and the pipe connection
and make shure they are clear.
I did buy a new O2 sensor and a new TW sensor and changed them. I think it pretty well leaves only the EGR passage ways as to what could be the culprit.
Thanks ecogabriel for the hang time. Hope you are havin fun at it. Quite rare to find someone who will share their time and knowledge and have the hang time you have exibited. Ill reply after next smog!!!
watch4it

[ecogabriel]

Most likely, there is one or two partially clogged EGR passages. If you saw the photos at the end of that document, you could see where the passages get clogged -where the runner gets in to the individual intake runners. Those are small enough to clog themselves with carbon. You could also see how hard is reaching them in our cars and those that came immediately after. Even if you reach them with a hook from the intake chamber I am not sure they can cleaned up completely.

Partially clogged runners would explain why you can still kill the engine when applying vacuum to the valve but fail emissions; exhaust flow reaches the cylinders but not enough during engine operation to keep NOx down. ECU does not detect anything wrong because the only test it does is for the valve sensor position. More modern cars (OBDII) test also EGR flow using other means.

Partially clogged EGR runners are a common failure for Hondas; you google them and they keep popping up.

TW sensor was not likely the problem; its only connection with EGR was telling ECU about engine temperature, and the test you did shows that it is working. It won't hurt anything though (except your pocket) and they are known to cause problems as some guys reported here.
02 sensors are a tune up item so if you do not remember when you replaced it it was a good thing to do.

Good luck

[Dr_Snooz]

I think you drill into the passages from the top of the manifold. There are little blobs of solder or something that you drill out. I can't find a pic. Clean up and then replace with a threaded plug.

[watch4it]

Most likely, there is one or two partially clogged EGR passages. If you saw the photos at the end of that document, you could see where the passages get clogged -where the runner gets in to the individual intake runners. Those are small enough to clog themselves with carbon. You could also see how hard is reaching them in our cars and those that came immediately after. Even if you reach them with a hook from the intake chamber I am not sure they can cleaned up completely.

Partially clogged runners would explain why you can still kill the engine when applying vacuum to the valve but fail emissions; exhaust flow reaches the cylinders but not enough during engine operation to keep NOx down. ECU does not detect anything wrong because the only test it does is for the valve sensor position. More modern cars (OBDII) test also EGR flow using other means.

Partially clogged EGR runners are a common failure for Hondas; you google them and they keep popping up.

TW sensor was not likely the problem; its only connection with EGR was telling ECU about engine temperature, and the test you did shows that it is working. It won't hurt anything though (except your pocket) and they are known to cause problems as some guys reported here.
02 sensors are a tune up item so if you do not remember when you replaced it it was a good thing to do.

Good luck

Downloading a pic of the last smog slip to photobucket. Sorry someone else had my handle "watch4it" so I used an ole stand by "Chokeyourchicken".
ANYHOW it passed this time. I think the sugestion of the O2 sensor as a tune up item was right. I had never changed it but I bought the car with 190,000 + miles on it.
I guess I will go through all the things it takes to clean the EGR Runners just to make shure MOST of the EGR system was addressed.
Thanks again 4 all the help I hope the Karma repays itself to you tenfold. Iam shure in debt to you. Good Job, Practise makes perfect.
Now I'll see 300,000 miles on this little beauty. Then I might try for 400,000.
Sincerely: watch4it
http://i984.photobucket.com/albums/a...0LX/img006.jpg

[watch4it]

I think you drill into the passages from the top of the manifold. There are little blobs of solder or something that you drill out. I can't find a pic. Clean up and then replace with a threaded plug.

http://home.comcast.net/~em-engineering/T2T013.pdf
Here ya go!!
Thanks ecogabriel:
watch4it

[Dr_Snooz]

Nice work! She's good for 400k, just don't give up on her.

[watch4it]

Nice work! She's good for 400k, just don't give up on her.

And I am glad I didn't have to borrow that hammer you are toting around with ya. Thanks for your help.
watch4it

[ecogabriel]

I'm glad you ended up passing smog and you can keep the car running. I had to retrace the thread to see the O2 sensor thing; they are cheap, we generally do not have the resources to test them (I don't have an oscilloscope) it is sensible to replace them.
One thing I like is that you ended up learning things by working instead (or besides) reading about them.

[phrenology]

SMOG FAIL

I had an EGR code on the ECU, ended up replacing the the EGR main valve/lift sensor assembly. The code/engine light went away and the stutter at idle RPMs mostly went away. I took it to smog today and it passed everything in the 15 mph range but failed the 25 mph range tests in NO parts per million blowing a 913. Compared to the previous owners smog at 617 in the same category. I'm not sure what the CA tolerance is in the NO readings but it's testing a lot higher than it did a year ago.

The tech said it was running lean in the 25 mph, I think the problem is also contributing to minor low idle issues. Any guesses? I'm thinking its an 02 Sensor throwing off the map? Its pretty much stock and I don't think any of the original sensors have been replaced. I'm at 117K, so things like sensors could be starting to fail now.

[phrenology]

Any ideas on decreasing high NO @ higher speeds?

[phrenology]

Gonna try to get this high NO reading sussed out next week.

[ecogabriel]

A short answer: running lean may be a O2 sensor on its way out. If you have no record when it was last replaced I'd get a new one; a universal-type runs about $20.

If you don't mind reading take a look at the links below; they talk about emission failures and most likely causes. They apply in general to our cars but there are some things that don't... I keep some of that info in my computer for reference

http://www.auto-repair-help.com/auto...st_failure.php

http://www.aa1car.com/library/tr1196.htm

http://www.asashop.org/autoinc/oct2004/techtips.htm

http://www.autoshop101.com/forms/h56.pdf (I found this and belong to toyota but it is good from what I have seen so far)

Sorry for not posting earlier I'm nuts running with other stuff so I don't log in as I used to


would you mind posting the results of your smog test?

[phrenology]

A short answer: running lean may be a O2 sensor on its way out. If you have no record when it was last replaced I'd get a new one; a universal-type runs about $20.

If you don't mind reading take a look at the links below; they talk about emission failures and most likely causes. They apply in general to our cars but there are some things that don't... I keep some of that info in my computer for reference

http://www.auto-repair-help.com/auto...st_failure.php

http://www.aa1car.com/library/tr1196.htm

http://www.asashop.org/autoinc/oct2004/techtips.htm

http://www.autoshop101.com/forms/h56.pdf (I found this and belong to toyota but it is good from what I have seen so far)

Sorry for not posting earlier I'm nuts running with other stuff so I don't log in as I used to


would you mind posting the results of your smog test?

Thanks for your help. I'll read more when I get home, and post up the Smog results.

[ecogabriel]

I found an article on how to diagnose EGR issues in our Hondas.

It has a way to test EGR valve sensors but I had discovered one anyway; what it is good is the description on how to clean the individual EGR runners. Also, it has a fast-track way to test functionality for 86-87s accords (88-89s are slightly different but there's a service manual for those)... It also described a problem I had recently (a lazy EGR) that is more typical (because of design) in early 3Gs than in the late ones.

http://img213.imageshack.us/i/hondaegr13.pdf/

Anyway, it seems that you may fix the NOx problem (if the failure is not by a large margin) with a new O2 sensor. That is the reason for posting all the links and whatnot; just keep them as reference (plus what it is here on how to check the valve itself)

[phrenology]

I already replaced the main EGR valve before I went to smog. I will try to copy and post my smog reports tomorrow. The smog tech noted that it was running lean at the 25 mph test when it failed the NO. BTW thanks for all the links.