I have a 1996 Saturn SL2, 104K miles. The engine runs rough and the #4 cylinder has a weak spark. The engine check light is on. A shop got the failure codes 420, 405, 341 and 304. I have replaced the plugs, plug wires, coils, ignition module and crank position sensor. Nothing helped. On rare occasion, the check light will go off and the engine will run fine for 10 to 30 minutes. I purchased the repair manual and it seems that there is nothing more to replace. What do you think the problem is? Thanks for your help.
P0420 Catalyst System Efficiency Below Threshold (Bank 1)
P0405 Exhaust Gas Recirculation Sensor A Circuit Low
P0341 Camshaft Position Sensor Circuit Range/Performance
P0304 Cylinder 4 Misfire Detected
your car dont have a camshaft sensor. are you sure u wrote down the correct codes? your car is 1996 so i assume its obd2. and i also assume those are generic codes and not manufacture codes. well based on those codes i assume your egr is tripping out causing the cylinder 4 to misfire. the camshaft sensor detects that jerky misfire causing the computer to think the sensor is reporting incorrectly. of course the cat cant handle the all that carbage the misfire caused so the o2 reports cat is not doing its job.
But ur car dont have a cam shaft sensor so it throws my theory out of the window
when does this misfire happen? during light acceleration? idle? wide open throttle?
Did you ever figure out what was causing the error codes on your '96 SL2? I have the same vehicle, with about the same mileage, and am seeing a nearly identical problem (Service engine soon lamp on, camshaft position code, and O2 sensor code). The car almost always stumbles during warm-up when the temperature gage passes the 1/4 mark, frequently causing the "Service ..." light to come on. The dealer service manager says this is the EGR valve openning. Now the lamp is almost always lit. I suspect the EGR is the root cause, and the misfire and O2 errors are symptoms of this. The plugs, wires, and EGR could stand to be changed, but I'm determined to avoid "shotgun troubleshooting". What was your experience? Thanks!
I think he/she is probably never coming back...and if he or she does come back, they'll only ask silly questions and say they they know better than anyone else lol....dont worry....:banghead: