2001 nissan quest shaking,and sometimes shut off losing power wasting gas,i did tune it up what could be

Question

I did a major tune up,timming,all belts,all oxygen senors, knock sensor,head gasket,gas filter,fixed air leaks,water pump,distibutor itself,spark plugs wires ebg valve,air filter,thermostat,gas cap,this about a year and half,recently I did the plugs and sparkplugs,the van feels like its losing power,wasting more gas,and shaking to the point now that its shutting off,only when I slow down or stop(idle) I have to put in n. And keep my foot on the gas so it won't shut off,and the only code I'm getting is p0300,what else can I check or change???

Answer 1

The P0300 code means that multiple cylinders are misfiring. There are many thing that can cause the misfire, injectors, spark plugs, spark plugs wires, head gasket. Unfortunately without testing the vehicle you will be just guessing what the problem is. Before changing more parts, you should try to diagnose the problem to find the cylinder(s) that are misfiring. You could start by performing a compression test.

Answer 2

your problem is most likely the bearing inside the distributor, its either seized or damaged and causing the camshaft senor disk to warp or move out of place. very common problem. take the cap off the distributor, than take the screw out of the rotor button, next remove the two screws that hold the cover under the rotor button, now grab the shaft and wiggle it side to side to check for play, there shouldn't be any movement.. it is also common for  the coil inide the cap to short out with the housing.

another common missfire problem is when the vehicle gets wet, water runs down the firewall to the top of the spark plugs and shorts the plug.