My wifes 97 Jetta has had this code twice now in the last year. Both times it would come on and clear it self. I did the spark plugs, wires, cap and rotor 20K ago. Everything is tight and the plug looks ok. Do you think it could be a bad injector? I was told that this could happen. I do run FP60 Plus every fill up. What about using no name brand gas stations? Im wondering if something got into the injector...what are the odds of that happing twice though.
Cylinder #3 misfire
- Thread starter ARB1977
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You say the plug looks okay.
I had a complete misfire on an olds van I brought home, it had an injector so bad (stuck open) the spark plug was soaked and you could hear it missing at idle. Was flooding out, etc. Of all the junk cars I've collected that's been the only injector problem I've ever seen. Naturally an injector could just have a different flow rate from the rest and not be totally dead as describe above...
If the injectors are easy to get at you can always swap them for other cylinders to see if the miss follows.
Can also make sure the plug wires are routed exactly right, etc.
I would google "Jetta P0303" and find a VW forum that's probably nailed this issue.
If its intermitant its going to be harder to locate. If there is another plug wire thats about the same length swap it with number 3 sometime as well. Just move one thing at a time though. I'm betting its the plug wire. I've had that happen more than once and thought injector but as the other guy said pretty rare. My last time with a similiar issue was on my mothers car. Plug wires were bosch I think and only about 1-2 years old. Just installed never taken off or yanked on. Just plain failed. This was on a mazda 626. A short trip from work to home 8 miles or so almost finished off the cat too. It smelled funny and threw a cat effeicincy code a couple of times and was OK after a few days after getting the wires swapped under warrenty. I found it by clearing codes and swapping the number 2 and 3 wires (its I-4) and the misfire code swapped cyclinders after I loaded the engine by doing a stall test.
Start it up at night in the dark and see if your wires are leaking any current. Stop using the FP60 and use a tier one fuel like Shell and see what happens. I have seen fuel additives cause problems with too much use might clog you cat converter. You may want to disconnect your precat and drive to see if it misfires. Just take earplugs. 
From the web:
A code P0303 may mean that one or more of the following has happened:
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer
From the web:
A code P0303 may mean that one or more of the following has happened:
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer
Last edited:
Originally Posted By: ARB1977
My wifes 97 Jetta has had this code twice now in the last year. Both times it would come on and clear it self. I did the spark plugs, wires, cap and rotor 20K ago. Everything is tight and the plug looks ok. Do you think it could be a bad injector? I was told that this could happen. I do run FP60 Plus every fill up. What about using no name brand gas stations? Im wondering if something got into the injector...what are the odds of that happing twice though.
Originally Posted By: mpvue
Originally Posted By: ARB1977
My wifes 97 Jetta has had this code twice now in the last year. Both times it would come on and clear it self. I did the spark plugs, wires, cap and rotor 20K ago. Everything is tight and the plug looks ok. Do you think it could be a bad injector? I was told that this could happen. I do run FP60 Plus every fill up. What about using no name brand gas stations? Im wondering if something got into the injector...what are the odds of that happing twice though.
Originally Posted By: PT1
Start it up at night in the dark and see if your wires are leaking any current. Stop using the FP60 and use a tier one fuel like Shell and see what happens. I have seen fuel additives cause problems with too much use might clog you cat converter. You may want to disconnect your precat and drive to see if it misfires. Just take earplugs.
From the web:
A code P0303 may mean that one or more of the following has happened:
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer
From the web:
A code P0303 may mean that one or more of the following has happened:
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer
Originally Posted By: ARB1977
Originally Posted By: mpvue
Originally Posted By: ARB1977
My wifes 97 Jetta has had this code twice now in the last year. Both times it would come on and clear it self. I did the spark plugs, wires, cap and rotor 20K ago. Everything is tight and the plug looks ok. Do you think it could be a bad injector? I was told that this could happen. I do run FP60 Plus every fill up. What about using no name brand gas stations? Im wondering if something got into the injector...what are the odds of that happing twice though.
I had a misfire on 1 of 4 cylinders due to a clogged injector in my Mazda. It was clogged so bad that it was not ionizing the fuel properly, thus the cylinder was not firing. I ended up pulling all of them out and spraying them inside and out with carb cleaner. Fixed the problem immediately and the car even feels like it runs smoother/has more power after this. I put the clogged injector into a different cylinder just in case it wasn't the problem (or if cleaning them didn't work), but it turns out that they just needed to be zapped with carb cleaner. You can also test the resistance with a multimeter and obviously the impedance should be the same in all of them. If one of them is off, it's probably bad. Also you can put a blade screwdriver to the metal part of the injectors and the handle to your ear, and listen for the "ticking" sound they make when firing, they should all sound the same. And don't forget to lubricate the o-rings and such before reinstalling the injectors, taking care not to get any oil into either of the ends.
Last edited:
Originally Posted By: mpvue
Originally Posted By: ARB1977
Originally Posted By: mpvue
Originally Posted By: ARB1977
My wifes 97 Jetta has had this code twice now in the last year. Both times it would come on and clear it self. I did the spark plugs, wires, cap and rotor 20K ago. Everything is tight and the plug looks ok. Do you think it could be a bad injector? I was told that this could happen. I do run FP60 Plus every fill up. What about using no name brand gas stations? Im wondering if something got into the injector...what are the odds of that happing twice though.
a misfire can be something other than fuel and spark! you also need compression. you could have a bad head gasket, rings, burnt piston etc.. if you cant find the source run a compression test. if compression is good you must also look at the emission system. on a 4 cylinder with exhaust gasses injected back into the intake stream if you plug up the passages on 3 of the 4 cylinders the 1 that is working will put too much exhaust gas in that cylinder and the mixture will not fire.
Originally Posted By: stroked93
a misfire can be something other than fuel and spark! you also need compression. you could have a bad head gasket, rings, burnt piston etc.. if you cant find the source run a compression test. if compression is good you must also look at the emission system. on a 4 cylinder with exhaust gasses injected back into the intake stream if you plug up the passages on 3 of the 4 cylinders the 1 that is working will put too much exhaust gas in that cylinder and the mixture will not fire.
It is not necessarily the ignition.
The fuel injector may be wacky.
You can swap it with another and see if the code reoccurs on another bank.
If it's a 4 cyl, put #3 inj.on 1 or 4, not 2.
Originally Posted By: mechtech2
It is not necessarily the ignition.
The fuel injector may be wacky.
You can swap it with another and see if the code reoccurs on another bank.
If it's a 4 cyl, put #3 inj.on 1 or 4, not 2.
How does the injector seal to the manifold?
Usually an 'O' ring. They can leak air in sometimes.
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