I got a the check engine light on my 1991 LS400 and the code is "71", which is a EGR System Malfunction. The car will all of the sudden idle real rough and then go back to normal. I read where the EGR gasket causes this. I have changed the EGR valve gasket and cleaned the HELL out of the EGR valve. The car is still running rough. Anyone had this problem and what was the fix?

 

I did the following to relieve the problem.

1) I took the EGR valve off and cleaned the HECK out of it.
(2 - 12mm nuts). I used (WD40) and a small wire brush
to clean it. I also made sure the diaphram could move up and
down.

2) I took the mounting bracket the held the EGR valve (2 - 12 mm
nuts and 2 - 12mm bolts). This bracket has a temp sensor on
the bottom. I also cleaned the heck out of this.

3) Bought gasket material to make new gaskets for the EGR valve
and the bracket.

4) I also found that the air duct hose from the air filter was
cracked. I used black duct tape to fix for now until I find generic
air duct hose.

5) Disconnected battery terminal for 1 minute to reset ECU and
clear check engine light.

Car is running great for the past 3 days and no check engine light.