P0302 on 1.8L 1999 Mazda Protoge??

[Clay]

Friend of mine at work has a 1999 Mazda Protege with a 1.8L 4 cylinder.

He recently had a code for a bad MAF sensor, so he replaced it. It seemed to run better, but now the car will not idle (ie have to drive it will two feet when off the gas/slowing down), and is throwing a code P0302, which means cylinder 2 misfire detected.

The plug wires are only a year or so old, he put new plugs in it at the same time. He took out the new plugs recently, cleaned them, and reinstalled with no change, then he took the old plugs back in, with no change.

any thoughts? things to look for??

thanks,
clay

[Matt86]

P0302 is a misfire code. If it has the dual coil set up, try swapping the ignition coils and wires to see if the misfire has moved.

[Big_P]

+1 to what Matt said. I don't exactly remember what that setup is, but if you can swap a plug wire around, try that.

You could use a stethescope and listen to all the injectors, if number two sounds different than the others then it may be your problem. But I doubt it, in my 6 year career of fixing cars I can count on one hand how many injectors I've had to replace.

[Clay]

ok, we can try that.

Today at lunch we went out to look at the car.

Car seems to initially start up and run fine, but after a few seconds the idle falls lower and lower until it almost wont idle. The computer is doing this. I manually bumped up the throttle and let it come back down. It holds a good throttle again, then the idle slowly falls down to where it almost wont idle at all.

I pulled all 4 plug wires, and they all had GREAT spark. This thing must be use an MSD type multi-spark system from the factory.

To me it seems like the computer is pulling the idle down. I just dont know why.