Lately my car has been having issues, where it just shuts off for what seems to be no apparent reason. Right before the car shuts off, the rpm meter starts to shake (going up and down a little bit). Also, it seems like the engine starts to stutter slightly. I'm not having any problems starting the car in general. There is no particular amount of time that I have to drive for the car to shut off. Some days I can drive for 15 minutes before it happens, other times I can go a few days and it not happen. The odd thing is that I can usually start it right up after it shuts off. If I do have to wait, I only have to wait about 10-15 seconds. Lately, it has gotten a lot worse. It seems that it drives fine the first time that I start it up, but once I turn the engine off and then start it up again, then it tends to shut off shortly after driving and will do so multiple times. This mostly seems like it is happening now whenever it has been restarted and I push on the brake while driving.
I am thinking that I have some electrical problems. Right now I am getting the following codes: 71 EGR System Problem and 14 No Ignition 1 Signal. Any ideas or suggestions would greatly help. By the way, I have a brand new starter and battery and the alternator is checking out fine. I had a friend suggest taking a look at the relays under the hood.
By the way, the car is a 1991 Lexus LS 400 with about 191,000 miles.