Expert: Sean Halliday - 12/6/2007

Question
Hi Sean -

I have a '96 Nissan Altima that started idling roughly only occasionally for about two weeks but ran fine between bouts.  It has now stopped running, sometimes starts but runs rough and dies when put into gear.  It really seems like fuel starvation but why was it intermittant before?  Would a fuel pump or clogged filter fail that way, or could this be a sensor?

Answer
Fuel pump will not do this.If it was,it would stop completely.Its more likely to be the EGR valve or a vacuum leak.I would also check the fuel pressure regulator.Remove the vacuum line and look for fuel leaking into the regulator.I have seen this before and the regulator will cause this symptom exactly,stalls and runs badly.You will need to run through the test procedure for all possible causes which are,fuel pressure test,spark test to eliminate the electrical system,vacuum pressure and obvious things such as plugs,fuel filter, cap and rotor,spark plug wires.Its got to be done by one thing at a time as there are many components that cause this so as not to throw parts at it until you fix it,its tedious but necessary.You will find the cause if you follow the right way.My advice is to get a manual for your car as they are about $20 and very helpful if you are gong to keep this car.It will take you through all you need to do to find the problem.You will need a vacuum tester and fuel pressure tester but thats not too expensive.One more thing is to look for a tear in the air intake rubber from the air filter as this sometimes happens on these cars.