BUILD THREAD EGR

[Rams18]

If you keep the computer-controlled QJet and HEI and the original PROM, the computer will adjust fueling and ignition on the assumption EGR is working, and it wouldn't be good if it wasn't. So you'd probably want to either take your chances with a rigged PROM that disables EGR, or ditch the computer entirely and install pre-computer QJet and HEI. But either of those approaches assumes you can get away with it in your state, inspection-wise.

Ok, thanks.

 

[Rams18]

EGR is and has been a crutch for the OEMs to introduce an inert gas into the combustion process, it is no longer needed with today's engine management systems. I am frankly not sure why anybody would try to keep these archaic emissions systems operating. The lean burn operating systems of the past are just that...the past. Today's EFI systems are so efficient EGR is no longer needed. If you are required in your state to have functioning emission system. I'm sorry for your luck!

Ok, thanks.

 

[78Delta88]

I'll check some other things to verify, but I don't think it should throw a code. When you have an O2 sensor in front and behind the Cat, the ECU will measure the difference.

The ECU kind of assumes that one of the O2 sensors has stopped working or out of range. This is also in there to stop typical efforts of defeats. It will throw a code and force you to keep the EGR in active working condition or can fail you in emissions, or toss engine into Limpy.

The 1986 system wasn't that advanced. The original plan was based on engine temperature and load. If engine at operating temp and car in cruise, (not idle or WOT), EGR would get vacuum signal and EGR would open. Engine cold or idle, stop/go city traffic, or WOT, EGR is off.

 

[Rams18]

I'll check some other things to verify, but I don't think it should throw a code. When you have an O2 sensor in front and behind the Cat, the ECU will measure the difference.

The ECU kind of assumes that one of the O2 sensors has stopped working or out of range. This is also in there to stop typical efforts of defeats. It will throw a code and force you to keep the EGR in active working condition or can fail you in emissions, or toss engine into Limpy.

The 1986 system wasn't that advanced. The original plan was based on engine temperature and load. If engine at operating temp and car in cruise, (not idle or WOT), EGR would get vacuum signal and EGR would open. Engine cold or idle, stop/go city traffic, or WOT, EGR is off.

Thanks for the info.

 

[Clone TIE Pilot]

All engines pretty much internally self EGR themselves at idle due to reversion, which is why the EGR needs to be shut off at idle. The reason some modern engines don't use EGR valves is because they use VVT instead to internally EGR such engines using valve timing overlap which sometimes causes coked up intake valves. Also some modern engines use EGR valves inside the intake manifolds and aren't serviceable for extra fun.