What is the purpose of an egr valve? - 1988 Chevrolet S-10

You have so many questions...First i would pick up a wotkshop manual .

Yes, you can clean it, although getting any interfering carbon completely out is difficult. to ck it without reinstallreinstall, use a vacuum pump. You should have one anyway to check the vacuum pot and ease of valve function.- Good Luck- Ned

I guess the answer depends on the purpose of the question.
Yes the engine can run without the EGR in place. If the EGR is removed and the engine started it should make a huge noise from the exhaust leaking. So you should not drive it with the valve removed.
The EGR valve redirects some of the exhaust gas back thru the intake to be reburned. That reduces emissions going out the tailpipe.

You cant,without the EGR having a clear flow you end up with a hole in your piston.The purpose of the EGR not only is it emission such as Nox.But it cools the combustion chamber.Ten year ago yes it interfered with power now the engine fuel stratedgy is to have a EGR,The MAF looks for the opening

P1406 EGR Valve Pintle Position Circuit Fault
This code is usually caused by carbon buildup in the EGR valve. The carbon deposits prevent the valve from closing completely.

After removing the EGR valve, clean the pintle seat area of the valve and the corresponding passageway in the engine.

or simply replace the EGR valve.

The purpose of you EGR Valve is to recycle un-burned fuel back into the engine, not only improving fuel economy by reducing the engines pumping losses, the EGR increases the mass in the intake; more mass means higher pressure, or less vacuum. Now the piston has less resistance during each intake stroke, which results in better gas mileage.

So if your EGR Valve is clogged, damaged or simply just not working - the those rich un-recycled fuels will make your car burn richer. (Which will make you burn more fuel.)

Hope this helps!

that sounds more like idler control valve, but the egr is in close position all the time, opens only when is in gear, and is controled by computer, rpms, etc. Thanks.
P.S. what you can do is to check if is open when the engine is off, is this is the case then you need a new egr. good luck.

Hi, this is your EGR pipe. The EGR system is an emission control that feeds combusted gasses back into the intake to lower the combustion temperature. The flow is controlled by the computer thru the EGR valve. Please let me know if you have more questions, and thanks for using FixYa.

Before you unpack the EGR you might be able to save the old one by cleaning it an then collect a refund. The purpose of the EGR is to supply a measure of exhaust gas to the intake mix so that the charge delivered to the engine is reduced in oxygen. This reduces the ignition temperature and prevent nitrous oxide formation in the exhaust. The EGR valve has two ports in it side by side. The one to the exhaust is gated by the valve and the other is connected to the intake. The valve is pulled open by a diaphragm acted on by a vacuum line from the intake manifold. The EGR valve is often monitored and regulated by differential pressure feedback exhaust DPFE sensor that lies upstream on the vacuum line leading to the EGR. If this DPFE fails it will report the same EGR light. Remove your EGR valve and plug the open EGR intake port on the manifold with a cloth and reconnect the vacuum line to the EGR valve. Start the car and now watch the action of the EGR valve. It should seen to open and close depending on engine demand. If it looks badly coked, spray it liberally with carb choke cleaner and wipe with a cloth until everything is polished metal. If the EGR looks good and is obviously working take a long look at the DPFE sensor; DPFE sensors have a reputation for failing many more times more often than the EGR valves they monitor.

Perform a valve clearance inspection and adjust if necessary. Tight or sticking valves will cause a misfire or rough running concern. Note: Perform valve adjustment when the engine is stone cold. 4cyl: INT 0.26mm EXH: 0.30mm (V6 engine are hydraulic and no adjust necessary.) Also check for a sticking or stuck open EGR valve. For diagnostic purposes only: Remove the EGR valve. Place a business card over the EGR passage and bolt the EGR valve back on. This plugs the EGR ports and if the misfire goes away the EGR valve is partially stuck open and is defective.
Check for low fuel pressure. Check for low compression. Check cam timing. Check for a weak ignition coil. Also don't over look the possibility of worn or broken engine mounts which cause excessive engine movement and engine vibration. -hope this helps

Your EGR valve appears to be leaking. The valve is most likly dirty or sticking causing the exhaust gasses to enter the intake manifold and causing the missfire. At highway speeds is when the exhaust gas is allowed in the engines intake system for combustion chamber cooling and emissions purposes.
I would suggest removing the EGR, cleaning the valve and have the valve checked.
Good luck.