My 1997 Nissan Altima GLE (Engine KA24DE) misfires on cylidner 4 (P0304 code) when the EGR system is attached. When the vacuum hose to the EGR valve is disconnected, the misfire completely stops. All the EGR components test OK on the bench. The car also seems to be calling for EGR right off of idle (in the 1000-2000 rpm range) as well as during normal operation (2000-4000 rpm range).
I've performed the following work/tests on the vehicle:
Replaced intake manifold gasket (upper and lower plenum)
Replaced spark plugs, wires, distributor cap, distributor rotor
Compression tested - all cylinders at 150 PSI (+/- 2 PSI)
Tested vacuum at intake manifold - meter reads about 18" vacuum and steady - revving the engine causes vacuum to drop slightly and then come back up to normal
Swapped fuel injectors for cylinder 2 and 4 to see if the problem followed the fuel injector and it did not - misfire continued on cylinder 4 even w/cylinder 2's injector installed
Tested resistance across fuel injectors (all injectors are at 12.0 ohms +/- 0.2 ohms)
Listened to injectors - all of them seem to be tapping happily away at idle
Adjusted engine timing to 20-deg BTDC
Adjusted idle speed to 750-rpm
Since the problem seems to be related to the EGR system, I also tested the following:
EGR valve (I applied a vacuum to it and the car began to stumble at idle as it should)
EGR BPT valve (removed from the car and blew into the bottom port while checking for airflow at the top 2 ports - the BPT seemed to function properly)
EGR Solenoid valve (removed from the car and tested the valve according to the service manual - it functioned perfectly)
EGR temperature sensor (appears to function within normal resistance limits)
Checked all hoses for leaks, cracks, etc.
have the same problem?
Monday, March 21st, 2011 AT 9:45 PM