Questions about EGR

[carcrossy]

1. What route does the exhaust gas travel once the egr valve sends it into the intake. Someone mentioned that there are 4 separate channels that take the exhaust to each cylinder. Supposedly these narrow channels can clog with carbon?

2. Leaks in the exhaust before the cat converter are supposed to introduce O2 which drives up nitrogen emissions. I have a pin hole in my egr tube. Would this be enough to cause my nitrogen emissions to go way up?

3. Will a hole in the muffler cause driveability issues. For example, will it cause back pressure to vary and make it hard for ecu to manage egr system?

4. How do you clean the filters on the BPT valve? Just spray them with carb cleaner?

5. Thanks.

Mechanical failures
In closing, I'll leave you with a pattern failure seen in '85-'92 Nissans, models 240 SX and Stanza, and some Hondas about the same vintage. They have individual EGR passages running to each cylinder. Eventually, some of these passages (one or two) will plug up with carbon while others stay open. The remaining passages receive 4-runner EGR volume, which is far too much and causes a misfire on the affected cylinders. It happens above idle and under load. Sometimes you can unscrew Allen head access plugs to clean out the passages, other times you must remove the upper intake plenum chamber to do the repair.

[idlafie]

1. What route does the exhaust gas travel once the egr valve sends it into the intake. Someone mentioned that there are 4 separate channels that take the exhaust to each cylinder. Supposedly these narrow channels can clog with carbon?

2. Leaks in the exhaust before the cat converter are supposed to introduce O2 which drives up nitrogen emissions. I have a pin hole in my egr tube. Would this be enough to cause my nitrogen emissions to go way up?

3. Will a hole in the muffler cause driveability issues. For example, will it cause back pressure to vary and make it hard for ecu to manage egr system?

4. How do you clean the filters on the BPT valve? Just spray them with carb cleaner?

5. Thanks.

Mechanical failures
In closing, I'll leave you with a pattern failure seen in '85-'92 Nissans, models 240 SX and Stanza, and some Hondas about the same vintage. They have individual EGR passages running to each cylinder. Eventually, some of these passages (one or two) will plug up with carbon while others stay open. The remaining passages receive 4-runner EGR volume, which is far too much and causes a misfire on the affected cylinders. It happens above idle and under load. Sometimes you can unscrew Allen head access plugs to clean out the passages, other times you must remove the upper intake plenum chamber to do the repair.

It would help if you posted a little bit more information about your car. Like what model year it is & whether it is stock KA or modified.

1). You can clean out the intake using a can of SEAFOAM. See YouTube for additional....

YouTube - The Official "How To Use Sea Foam" from Sea Foam and GUY. (http://www.youtube.com/watch?v=D11ZVYwj62w)

2). A pinhole leak in your EGR tube might cause your NO readings to go up, however it might not be the cause for your high NO readings. High NOX readings is the result of your Exhaust Gas Recirculation, (EGR) system not working. You could have a cut, melted or split vacuum line or bad soleniod somewhere in the EGR system...You'll need a Factory Service Manual to trace the lines & fix the problem.

The purpose of EGR (Exhaust Gas Recirculation) is to reduce the NOx emissions by putting a portion of the vehicle's exhaust gas back into the intake manifold so it mixes with the fuel and air in the combustion chamber. Air is mainly made of oxygen and nitrogen (O2 and N2). At temperatures above 1300°C (2372°F), these molecules split apart and rejoin with each other to make nitrogen oxides (like NO, NO2, etc...).

By adding hot exhaust gases into the combustion chamber, you are lowering peak combustion temperatures. The lower temperatures prevent the O2 and N2 from splitting and combining. Even though the exhaust is hot, about 600°C (or 1112°F), it's much cooler than the 1300°C required to make NOx.

In summary, the exhaust adds mass, increasing the heat capacitance of the mixture (i.e. making it harder to heat up the mixture in the cylinder). Peak temperatures are lower, reducing NOx formation, which ultimately reduces smog in the environment.

3). A hole in your muffler will not cause driveability issues. All it will do is make your exhaust louder so anyone in a 1/4 to 1/2 mile radius will hear you coming before you get there. If you have driveability issues, try doing a tune up. Change your distributor cap & rotor, along with your fuel & air filters. Replace your spark plugs with the recommended heat setting & make sure they are properly gapped, (.39 to .44 or is it .039-.044..???...see your FSM). Use your Factory Service Manual to set idle & timing. Follow the exact procedure listed in the FSM to make sure your idle & timing are set properly.

4). Using Carb Cleaner should work to clean your BPT valve. You should also check & clean the SOLENIOD valves running to your BPT valve. They control vacuum running to the BPT & EGR valves. Make sure none of the vacuum lines are cut / torn / melted or missing. If they are fix or replace them. Use your Factory Service Manual to trace the vacuum lines along with how to test your Soleniod valves. If the Solenoid valves are not functioning properly then you WON'T get any vacuum to the BPT or EGR valves, resulting in high NO readings.

Anyhow, if you use the SEARCH function here on Zilvia you'll find plenty of responses I've posted to people's smog problems...Here's one of them...
http://www.zilvia.net/f/tech-talk/59074-runnin-rich.html.

Anyhow, hope this helps....

ID

[carcrossy]

Thanks for the reply. I appreciate it. My car is a stock 1992 manual 240sx.

The EGR works when I apply a vacuum to EGR: Car will stall during idle. When I race the engine, the EGR moves up a few millimeters. I'll have to check if it is not rising enough.

My EGR does not come on during idle which implies that the egr solenoid works since the computer has to send power to solenoid for it to close off vacuum to bpt/egr.

I also have high HC and CO during driving test. I guess a ton of things could be doing this.

During idle my CO is ok but the HC is high. THey dont read NO during idle.

I already read some of your othe posts on cleaning egr and theory and I appreciate it.