EGR functions, questions and more...(have searched)

[CDE]

Hi...I mostly talked to Nistech about this problem before...I have been all over this site, and have learned quite a lot about my 240 (89, ka24e). My problem was that I was having a slight shimmy starting around 80 kph (at slight acceleration). I have been reading for several months now and got together with an old buddy that has had some mechanical experience. I told him of my problem and he tried a few things before we finally came up with the possible problem. It was the EGR valve...



We unplugged the hose from the top of the valve, and plugged it.



Viola, no more shimmy at 80kph. He thought that this might possibly mess up a few things once I plugged the hose, but wasn't sure. It just would disable the EGR...? He had this problem with old chryslers or something, but it was at a much lower speed and that's where the idea to do this came from. Anyways, I have read up on every EGR thing on this site but I still have a few questions.

I did the test where I would run the engine at 2k rpm and push the diaphram up on the egr. THe engine did sputter and almost died. It seemed to have a more adverse effect when the engine was at just an idle. From what I gather that means that it is working properly....But what exactly is that hose for that I disconnected? should I also cap the valve where the hose was connected?

The car is also running quite rich. I get crappy milage. I had planned to do a fuel filter change, as well as new O2 sensors to help get a bit more milage, but from what I've read this wouldn't effect milage all that much.

And also, what is this little thing on the hose that's connected to the egr? I was going to take the EGR off and clean it with carb cleaner tomorrow, but I just wanted to know some more info.



And just one more thing...I had an exhaust problem - sounds like a tinny rattle when I accel, and am thinking something either the resonator or cat is pooched. Could a plugged cat cause weird backpressure that would mess up things like running rich and a wonky EGR? My line of thought points toward the exhaust system because the EGR passed the push-n-almost stall test.

What are your thoughts? (anyone...)

Thanks in advance,Chris

[JoeKansas]

I just had the egr valve off of my ga16i engine a few days ago. A simple vacuum pot controlling a cast iron bodied valve. This is how the Chilton book describes it's theory of operation: EGR system is used to reduce combustion temperatures in the engine thereby reducing the oxides of nitrogen emissions and controlling detonation (ping). Recycled exhaust gas is drawn into the intake manifold from the exhaust manifold with the flow controlled by the EGR. As the throttle valve is opened, more vacuum is applied to the egr valve vacuum diaphragm. The diaphragm moves a tapered valve, that allows exhaust gas to pass into the intake manifold.........edit some blah blah blah.......The system does not operate when the engine is idling because the exhaust gas recirculation would cause rough idle at low rpm......

Anyway, my engine has an EGR control solenoid. That could be causing your problem (if your engine has one) because it could be telling your EGR to open and when it shouldn't be.

[CDE]

I had a rough idea of what the EGR did (but thanks for the explanation), and is that pic of the little cylender which is about the size of a quater (circumfrence wise) - is that the solenoid?

[s13sr20chris]

that plastic valve is just a one way valve. the nipple on the top is as joe says for vacuum to open the valve. you should also have a bpt. that stands for back pressure transducer. it is part of the control circuit.

[CDE]

I was going to take it apart and clean it, but since it almost stalled when I pushed up on the diaphram, that means the EGR is functioning properly???

And my other main question was if the exhaust is plugged and has too much back pressure, would that cause the EGR to function when it's not supposed too? Or would it be the control solenoid that's malfunctioning when that happens, or possibly the BPT? I mostly understand the idea of the whole EGR system, but I'm just trying to figure out how they work together. The reason for my problem seems to be that vacuum line that I unplugged from the EGR and I'm just trying to figure out what's causing that. The BPT is seemingly working properly...I don't have a vacuum gauge so I can't be sure...

[NISTECH]

When pushing up on the egr that just tells you it will flow when the Solonoid regesusts it to providing the Bpt closes its vaccum vent sending vaccum to the egr valve.

[s13sr20chris]

right, to rephrase what nistech just stated...if you push up on the diaphram and she stumbles, it just shows that the egr CAN work properly. the control circuit still has to work properly too. plugged exhaust will cause more of a problem on its own than the miniscule effect it would have on your egr operation. it is possible to have too little backpressure and not get enough egr flow but that wont hurt performance one bit.

[CDE]

Thanks for the info!

I'm thinking it's more of a control valve issue then.

I've been getting VERY bad milage out of my 240 - only 320ish KM out of a 38 or so Litre fill up. On my last tank, I unplugged that hose about 1/4 thru the tank, and now I'm at 380 and still have a good 40 or so K left in the tank...The next fill up will be able to tell me whether or not it has made a huge difference or not but I didn't think an egr would effect milage so much from what I've read.

Thanks for the responses once again...I'll post my milage difference after my next tank of gas..

[NISTECH]

Thanks for the info!

I'm thinking it's more of a control valve issue then.

I've been getting VERY bad milage out of my 240 - only 320ish KM out of a 38 or so Litre fill up. On my last tank, I unplugged that hose about 1/4 thru the tank, and now I'm at 380 and still have a good 40 or so K left in the tank...The next fill up will be able to tell me whether or not it has made a huge difference or not but I didn't think an egr would effect milage so much from what I've read.

Thanks for the responses once again...I'll post my milage difference after my next tank of gas..

Something to ponder:Funny how a device designed to help reduce pollutants and reduce amount of fuel emissions out the tail pipe can actualy create a problem with excessive fuel consumption [increasing pollutants 10 fold] when it malfunctions. The irony...lol

[SidewaysAndHighways]

What would happen if you just plugged off the EGR? Anything Bad?? I Don't have enough backpressure to open my EGR so I tried bypassing the BPT, and it worked, but it sputtered under speed holding throttle so I switched it back so it would run smoother.

[NISTECH]

What EGR does is recirculate the exhuast,basically giving volume to the cyl but reducing the amount of oxygen to combine with the nitrogen. This reduces Nox emission which can create photogenic pollutants [ the haze you see in the air] If you have the situation he has going on you are still cutting back on the Nox but your CO and Hc is going through the roof. CO is what causes health issues. So its kinda a trade off. but going with out it wont be real bad but will contribute to the photogenic emissions you can see. You still have some control as long as you still have the cat installed. But it does not do as good a job as the EGR does controlling the NOx.

[CDE]

Something to ponder:Funny how a device designed to help reduce pollutants and reduce amount of fuel emissions out the tail pipe can actualy create a problem with excessive fuel consumption [increasing pollutants 10 fold] when it malfunctions. The irony...lol

I thought it was quite ironic also...lol.I bet I will still pass emissions because I plan to get a nice new big cat on my new exhaust system. I will also have to get an air-care certificate (emissions test) because I'm moving to a part of my province that requires it. I'm hoping with the EGR diconnected I can still pass air-care...if not I'll just plug it back in and get them to retest right away...heh. AND...if that doesn't work I guess I'll actually have to break down and buy a control valve.

Sideways - that sounds like what my car was doing...except the opposite! Did you plug the same hose as I did?

[NISTECH]

Are you familier with the test? do they test it on a dyno? If so it will measure Nox. The rhodium bed in the cat is not strong enough to clean up all the Nox a car wil emit. Running a tad on the rich side will help drop the Nox though as it cools the cyl a bit. Nox needs 2 things to form, Heat and pressure. Removing your t-stat could also asist in bringing down those temps a bit. I dont know their proceedures up there for smog testing but here in california, we are to wait till the car reaches full operating temp to test. So there are a variable of issues here you could encounter. Being to rich will cause you to fail for CO and HC being to lean will cause you to fail for HC and NOx as a lean condition can bring on the heat in the cyl. [The more oxygen the hotter the fire] Without a gas anaylizer its really hard to nail the mixture right. If they only do a 2 speed idle test[no dyno] then Nox is not measured and it is purly a visual inspection and maybe a functional check of EGR.

[s13sr20chris]

What would happen if you just plugged off the EGR? Anything Bad?? I Don't have enough backpressure to open my EGR so I tried bypassing the BPT, and it worked, but it sputtered under speed holding throttle so I switched it back so it would run smoother.

yeah, dont bypass the bpt. you will just be losing power and creating more emmissions. my motor is a non emmissions motor and i dont miss my egr one bit.

[CDE]

Are you familier with the test? do they test it on a dyno? If so it will measure Nox. The rhodium bed in the cat is not strong enough to clean up all the Nox a car wil emit. Running a tad on the rich side will help drop the Nox though as it cools the cyl a bit. Nox needs 2 things to form, Heat and pressure. Removing your t-stat could also asist in bringing down those temps a bit. I dont know their proceedures up there for smog testing but here in california, we are to wait till the car reaches full operating temp to test. So there are a variable of issues here you could encounter. Being to rich will cause you to fail for CO and HC being to lean will cause you to fail for HC and NOx as a lean condition can bring on the heat in the cyl. [The more oxygen the hotter the fire] Without a gas anaylizer its really hard to nail the mixture right. If they only do a 2 speed idle test[no dyno] then Nox is not measured and it is purly a visual inspection and maybe a functional check of EGR.

I honestly have no idea how they test it...for the 20-30 dollar charge I don't think a dyno is involved...As far as I know, they just hook up a computer to the end of my tail pipe and test emissions that way. I'm just moving down to the coast (Kelowna BC to Langley BC) and here in k-town I've never needed aircare...My last car didn't even have a cat!

I know Cali is pretty anal about emissions. I'm pretty sure the "aircare" on the coast is a little more slack. I'm going to fill up with Chevron premieum and take it when i'm a good ways thru the tank...I just don't want the headache of not passing even with my egr reconnected. But from what you're saying I should be fine because my car does run a teenie tiny rich.