johnblagg

Ok I getting a egr code 71 ...but the valve is fine took it off cleaned it and tested and replaced it ....what else cold cause the code 71 ...I have noticed that suddenly the fuel tank seems not to be pressurising like it was last week ?

I am not noticing any rough idle but when I apply vacuum to the egr valve itself it just slows idle down and dosent really make it stumble?

mdbrown

My car doesn't have an egr valve so I'm not real familiar with the ones used on the ES but often the egr valve itself isn't the issue but the sensor built in it is actually the failure. You will still need to replace the valve assembly if that's the case.

johnblagg

The temperature sensor is seperate and does not require replacing the entire egr.....

1992 es300 by the way ...im wondering since the temperature sensor was only on the california model about just using a resistor in its place to get rid of code and leaving the rest alone ...does the code trigger a different timing map or change anything ?

mdbrown

Not necessarily talking about a temp sensor, lots of egr sensors have a sensor that measures how far they open and how long they stay open. When that sensor fails the ecm thinks the egr is no longer working.

johnblagg

this model has not got that either ...the only sensor I have found is the temperature sensor and if I bypass that with a resistor ecu thinks everything is fine.

Im wondering what the results are to this since only the California version of this model had that sensor at all

johnblagg

so far the only reason I can see for the code is the temp "probe' sensor for the egr gas temp ...have not got hold of a meter to test it yet to see if it is in fact bad ...the code started out intermittent and has now became a constant so for now I guess Ill bypass it since I have not taken egr tube off to clean it out yet .

johnblagg

OK I was sitting thinking about the problem and it hit me ...the bimetallic vacuum valves ?

I had totaly skipped over them while looking at the problem and when I pull the lines to check them they both seem bad ,I can blow air right through with them cold and they should be closed when cold ?

The one going to the egr valve itself also lets air suck in through the little filter cap ontop of it so is a vacuum leak .....and shoot they think these things are made of gold

The one going to the charcoal cannister would explain the sudden fact the gas tank has no pressure build up since it is full open at all times letting vapors vent out

johnblagg

well I decided that since the tvv valve that goes to the egr seems to do nothing other than shut off vacuum to egr untill the engine has warmed up past a certine temperature. It seems redundant since the egr actually operates depending on the amount of vacuum the engine is generating and seems to work just great without this valve at all .....anyone that can give me any reason it is necessary is welcome to chime in here and help me on this one?

Upon doing so I find my egr code has gone away and I did two test drives of 10 miles each to see if it was actually working correctly.One from a cold start and no issues at all present, no rough idle no problems I could detect....I waited about 1/2 hour and another test drive with engine not really cold but not fully warmed up ....again no issues and no egr code. I dont see any reasone to spend $70 for this one if it does not actually have any real effect .....

I will drive a day or so checking for the code to see how she does and then go to work on the charcoal cannister valve issue and see what I can do about that one ....

mdbrown

The purpose of the egr valve is to lower the combustion temperature to prevent the formation of nox so it could create some driveability issues when the engine is cold.

johnblagg

actually the tvv valve only keeps the egr vacuum shut down untill the engine warms up, and at idle its my understanding that the egr is not active anyways so I dont see it doing that,and in fact so far it hasnot ....code is gone and she is running just great but tomorrow morning will be the real proof on that since it is getting down into the 20s tonight and the first start up tomorrow will tell the story.

The way it was there was no vacuum at all to the egr so it was in fact effectively deleted and may as well have not existed at all.But at the same time the ecu would have seen a lean condition due to no exhaust gas recirculating causing the o2 sensors to tell the ecu to enrich the system and cause mpg to suffer due to the faulty reading from what I have gathered from reading the posts on this and doing lots of reading on forums everywhere trying to learn this engine and how it is supposed to work when its all functioning correctly.

How can it actually working now cause a drivability issue?Unless it was stuck open all the time "which it is not" there will not be a issue with drivablility when it cold.

It was throwing the code because the temperature sensor on the egr was not being heated up due to the valve not opening at all previously due to a total lack of vacuum which had to be affecting more than the egr system in fact and causing other issues although I have not noticed any other issues ,and mpg has been improving with every thing I have done so far.

mdbrown

Actually a non working egr system shouldn't create any issues at all with the car and shouldn't effect fuel mileage at all. The egr system is much like the evap system in that it doesn't add anything to the performance of the car. The only time the egr system is an issue is if it's stuck open or opens too early, otherwise you shouldn't know it exists.

johnblagg

There seem to be a lot of people on both sides of the egr issue fence on that,some claim it helps ...some say it lowers ...I say it is required in some places and not a choice,and while It is not a issue right where I am It is on the car and It will operate since the ecu in this vehicle is programed to function with it in place and it was minor work to fix it...and who knows my learning how it works and where the parts affecting it are located and how to at least bypass them to get it functioning may just help someone else .

Today from a cold start there is absolutly no drivability issue and the code is gone so the egr seems to be working just like it should ...problem solved and for a couple of hundred dollars less that the parts would have cost me at that ! In time as I have time and funds I will get the parts and replace them but untill then It is running well and has no code ....pretty good patch job if I do say so myself.

mdbrown

As long as you aren't experiencing any issues then you are fine. Yes, it is a requirement anywhere there are emissions tests. As for effecting performance or mpg, if it does at all it's a negative and not a positive. It works by routing a portion of exhaust gases back into the engine to lower combustion temperature (thus preventing the formation of oxides of nitrogen). If it's working properly then it will not make itself known at all, if it fails in any way at all then it can possibly have a detrimental effect on performance or mileage... it will never be a positive at all.

johnblagg

Hmm well I fixed it and mpg went up a couple mpg actually got 19.2 today in mixed driving.

Like I said I read statements to both effect all over the net. some for, some against, and some saying no one realy knows ....I ordered the modulator vavle new today just because although my repair is holding up and it is working they make a different one for diferent models and I assume spring tension and the diaghpram itself allows more or less travle in order to controll the amount egr opes or closes and when it gets in will see if it helps or not ..in fact may dissconnect egr just to compare the difference for myself .

So Far evey thing I have done has made a positive difference including restoring egr function .

Replacing knock sensors as well and from what I read everywhere my es300 should be running in limp mode since they are both throwing codes and totaly dissconected from the system since the wiring harness is totaly shot that goes to them, and I have the wires cut back to where they are still good and just shorted to ground in effect telling the ecu they are crap so according to everything I have read the ecu should have went to limp mode and she should be running like total crap and have no power at all and lol certinly not be getting 19 mpg and have plenty of power to zip around.......