Hi. My 2002 base auto with 57k miles started missing at idle and I thought maybe bad gas as I just bought it off of an old lady so I added some 93 and continued to drive it as my mechanic friend said to do and now it's began to miss under load and my cel came on and has a current code for the rear knock sensor which most stuff I read means it's likely bad but could this cause my misfire? Any suggestions would be greatly appreciated and thanks.

 

Causes could include spark plugs ( bad plugs, or wrong plugs) timing, fuel mixture, gasoline properties, bad knock sensor, etc.

There’s plenty of mechanically skilled members of the forum who may chime in. I’m more a hobby guy, and if it was me, I’d start at the local garage and have them hook up their scope. Spend $100 and then decide what to do.

 

Welcome to the Forum and your recent purchase…your misfire can be caused by many things so if your mechanic friend has a scan tool I’d start there…you can use the DIC to access your trouble codes…without wasting money on guessing what’s wrong take your car to a diagnostic shop…not a repair shop and certainly not a dealership…both are not equipped to diagnose cars only change parts…where are you located ??

 

If the only code you are getting is a knock sensor could I would wager that's a symptom not a cause. What code is it for the knock sensor?

As far as your miss fire I would bet the previous posters are correct in the spark plug and or wire guess. If you want to check it here is my suggestion:

Since you have no p0300 or specific cylinder code you can unplug one fuel injector at a time while running to identify what cylinder is not producing power. You can also do this with a scan tool with bi directional controls usually called cylinder deactivation or something similar. This only really works with a constant miss, intermittent miss is a bit harder. lowest or no RPM drop that's the cylinder to look into. Once you have your cylinder, pull the plug on it and look for scorch marks down the porcelain. If you see scorch marks that don't rub off bad plug. Other slightly easier test is lightly spray your spark plug wires with water, If it starts missing like crazy bad wires.

Like the previous posters have said there are a ton of other potential causes clogged injectors etc. Most often a hard miss is going to be a bad plug and or wire. If you feel confident enough you can try the above if not, I would recommend finding a good diagnostic shop.

 

Get an IR thermometer and take temperatures of each exhaust manifold as it exits the head. If a cylinder is missing it will be colder than the cylinders that are reliably firing. Once you have identified the misfiring cylinder(s) start swapping the following items one at a time from the bad cylinder to a good cylinder: plug wire, spark plug, ignition coil, and fuel injector. If the miss follows that part you have found your problem and know what to replace.

 

You said missing, does it stall and shuts off?

 

It throws p0332 and I'm gonna try pulling the injectors an look at plugs and wires. Was gonna change a that this coming week anyway. Doesn't stall and is a steady miss