Using an EGR restrictor plate to minimize the lean miss is a cool fix. I have been running with the egr vac line plugged and being constantly reminded by the CEL. When emmission test time rolls around
all that is needed is to replug the vac line, easy. I don't know if I'll pass with the restrictor plate and don't want to go through an annual plate jockey for testing. Has anyone tried using a vacuum
delay valve on this problem? You know the little check valves of the 70 's and 80's. Thanks for any feedback

 

If the EGR/EVP doesn't respond immediately to the computer's vacuum inputs, it'll still throw a code & turn on the CEL.

 

[updated:LAST EDITED ON 19-Dec-02 AT 07:30 AM (EST)]Dude, Go ahead and put the restrictor plate in.. That way the EGR valve will move when it needs to and the EVP sensor will think it's working properly and you will NOT get the CHECK ENGINE LIGHT!!
You get rid of the lean mix miss and it will pass the emissions test too!!! Sniffer tests on the exhaust are at idle and the EGR is closed at this point>> Install the egr blocker plate!!!!!!!!!!!

ftwfred

 

Not all emission tests are at idle. Depends on state and the area. Mine (Northern VA) is tested at 25 MPH for a few minutes, then at 35 MPH for a few minutes. As I recall anyway. I think other regions in the state don't even have emissions test.

Don't know if EGR is open at those speeds; my guess would be yes -- engine is hot, not at idle nor at WOT.

Raul

 

I tried pluging the line too, then made a plate for the egr. It ran better with the plate and gets much better gas milage than with the line pluged. I don't know how that affects milage, but it sure does. That plate is the best thing I ever put on the truck. I spent years and many dollars trying to cure a lean miss. It would run ok for about 8-10k miles if all the ignition components were new and the injectors clean. As the truck got older, it was more difficult to keep it running right. I found this forum and read about the plate and it now runs better than it did new.
Bill
'91 F-150 4x4, 300, 5 speed trans

 

So long as its not blocked its still working, so it is still recirculating the exhaust gasses. This is a good thing!

BTW, the only way an EGR system would lower the amount of lean missing you've got is because you're not compounding a normal lean condition. If you are running stoichiometric, you aren't going to have much leftover air in the CC after it fires. Exhaust gasses are inert so when they get recycled, you aren't leaning it out any because you aren't adding any more oxygen. The problem is that when you're running lean normally, you will have leftover oxygen, and when it gets put back into the chamber, you're running even more lean. Continue the cycle.


-=Whittey=-

 

You all have gotten me interested in this EGR Restrictor Plate. I've been trying to find an earlier post where somebody tells exactly what it is and how to do it. So far, I haven't found the information. Can somebody help me out here?

Thanks,

Meck

 

From my understanding of modern fuel injection, whittey is exactly right. What makes this engine skip when there is a malfunctioning EGR valve is the fact that too much exhaust gas is being let in because the valve is leaking. If anything, the more exhaust gas, the *less* lean the mixture is. When you block off the EGR, you're actually getting more lean because the exhaust is inert.

Engineers found that when cruising (not idle or WOT, it runs like crap) that they could meter out the fuel very lean and still provide plenty of power, but the lean condition produced excessive NOx emissions, because the combustion in this situation is so hot. To cool the combustion process, the EGR lets inert exhaust gas in, bringing the mixture back to stoich. Think of it, perhaps, as the exhaust just being a space filler, effectively reducing your displacement. Less fuel and fresh air combust efficiently in the same space, for better fuel economy.

Anyway, I had the same problem, but the truck is so old and we plan to use it so infrequently and off-road that when the EGR tube broke, I just put a pipe plug (standard thread, available at the hardware store) in the fitting in the manifold and capped off the EGR valve inlet. I can't believe how much better the truck runs without exhaust leaking in at idle, but of course the check engine light is on. (Do I care?)