Nissan Repair: nissan computer code, gas mileage, service engine soon light

Question
I have a Nissan 1997 Sentra. 1.6L automatic, 122,000 miles, uses no oil and I maintain regularly that has the service engine soon light comes on, stays on and then goes off after some time. In the last year it has been on about 8 times. I have asked many people what the code means and  can not get an answer that corrects the problem. The code is always 400 "Flow Malfunction". I change all filters, fluids, plugs, etc. myself. As of late the car hesitates every now and then from a cold start and then goes on with no problem. This problem has not affected gas mileage. Any answers???

Answer
hi dan.  well i did some research on your 97 sentra and i have found that an error code of 400 is caused by a faulty egr and to fix this is to replace the egr and/or back pressure tube.  i hope this helps, its the best i can do
for now.  good luck!

btw...welcome to the "whats causing this hesitation in my nissan now..." club.  ;)