akimber

On my 1996 Chevy c1500 pickup, 4x2 and 5.7L 350. I recently got this P0302 error code. Spark plugs are less than 10000 miles old. I changed out the spark plug wires, swapped spark plugs between cylinder 4,2, changed distributor cap and rotor. I had AutoZone clear the error but it still comes back after about 2 minutes. At lower speeds the truck sputters a lot. Has any one had this error before and knows what the possible cause might be? Any suggestions are appreciated.

kcb37

What kind of gas do you put in it? The computer can tell you which clyinder is misfiring by vibration. If you have a bad knock sensor it would cause vibration and poor idle or not be very drivable. I don't know how to check these but it is a thought. The knock sensor will adjust timing so you don't have a preignition. Good Luck

akimber

Last night I put in a can of B-12 Chemtool and a half tank of Premium gas (usually i put in regular) hoping it would clean out my fuel ejectors. I drove around last night for 20 or so miles with no change, then another 20 miles this morning, but still no change. I'll check on the knock sensor tonight. Is there any way to check to see if the fuel ejector is working properly?

NCHEVYHEVN

The gas is not going to be a problem. All you need is 87 and anything higher is just waist. And thinking if you run higher octane that it will clean out the system is silly also. Just go get a fuel system cleaner and pour it in the gas tank.

GMJunkie

Change coil packs around and see if it throws the same code on a different cylinder. It could just be a bad coil pack.

NCHEVYHEVN

It only has 1 coil pack and a distributor.

kcb37

If the knock sensor is bad better gas can help, sometimes. I only say that because the knock sensor adjust the timing to keep the gas from igniting to early. If it is going bad then a higher octane will not ignite as soon and may get it to run better.

NCHEVYHEVN

What are you talking about? The octane rating is how much the gas can be squeezed before it detonates and last I checked timing doesn't change the compression ratio of a motor. Just changes when the sparkplug fires.

kcb37

NCHEVYHEVN when you have a high compression engine you need a higher octane so you don't have pre detonation, on a fuel injected, and I belive a throttle body, the knock sensor will change the timing so you can run a lower octane. If the Knock sensor goes bad and won't adjust the timing then 87 octane may not work, but if you put in 91 it has a possablility of running better because the timing won't need adjusted to make it run right. But then the knock sensor could just be all messed up and a little higher octane rating wouldn't do anything. If you can't figure it out from this I don't know what to tell you.

kcb37

akimber
I am curious, do you pull a lot with this? If you do how much weight?
I'm kinda thinking, cause you changed your plugs and your wires around, you don't really have anything else to make one single cylinder misfire.
But if your valve seats or valves themselves were bad it wouln't get the full effect of fire. It wouldn't hurt to do a compression test.
I think this is kinda a reach and probably not it but worth looking at.
Good luck.