Check engine light illuminated, error code 303? I have replaced Wireset,Spark plugs, Coil is good. Not sure what is the problem. Can you please assist me? Thanks

On yours, it's a misfire. Plug, wire or coil pack. Have the codes read. this will tell you where to look. 301 is 1 cylinder 303 is # 3. and so on. Pull the wire off the coil, have it close, no spark, replace the coil. Spark, do a tune up. Plugs and wires.

From a reputable repair website:


P0351 - OBD-II Trouble Code

Auto Systems and Repair

Ignition Coil "A" Circuit Primary/Secondary Malfunction Our emissions expert has put together the following information about the P0351 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.
OBD II Fault Code

• OBD II P0351 Ignition Coil "A" Circuit Primary/Secondary Malfunction

What does this mean? The ignition coil or coils are responsible for igniting the air/fuel mixture inside the combustion chambers. Without reliable performance from the ignition coil(s) the vehicle will stumble and misfire.
Code P0351 indicates there's an electrical problem in either the primary ( the computer side ) or the secondary ( the spark plug side ) of the Ignition Coil "A" Circuit.
Symptoms

• Check Engine Light will illuminate
• Engine idles rough
• Engine misfires on acceleration
• In rare cases, the engine may not exhibit noticeable symptoms

Common Problems That Trigger the P0351 Code

• Defective Ignition Coil(s)
• Defective Spark Plug(s)
• Intake Manifold Vacuum leaks
• Carbon buildup in the Throttle Body air passages
• Defective Idle Air Control Valve or Electronic Body

Common Misdiagnosis

• Ignition coil(s) replaced when cause of the malfunction was a vacuum leak
• Spark Plugs replaced when cause of the malfunction was a vacuum leak

Engine misfire code probaly have a coil or plug wire going bad

Hello Frybird.

The codes you have are engine misfires.
Code 300 is random misfire (could be any cylinder).
Code 302 is cylinder #2 misfire and 303 cylinder 3 misfire.

Most common causes are ignition issues.
Spark plugs, ignition wires/boots and ignition coils.

Next would be fuel issues such as fuel injectors.
Next would be emission components such as EGR valves.
Then in a worst case condition would be engine wear parts (valves, camshafts etc.)

The place to begin is ignition as this is a common failure on most cars.

If you need further assistance regarding your question please ask me here in a comment.
Thank you for using FixYa.

KL

Get the codes checked.This will tell you what cylinder is causing the problem.If the wires and plugs didn`t help then you probably have a bad coil.Hope this helps.Good luck.

Could be, but more likely to be fuel. Why do I think that? Carbon build up typically happens when plugs are working (no carbon without fire) but fuel mixture is wrong (air or fuel). If coil, most likely would misfire at all engine RPM, not just low RPM. So, I reckon to look at fuel rail pressure to the injectors first - get a pressure gauge on the fuel rail and check it out. I think, but can't remember for sure, that there is a fuel pressure regulator per bank, but I could be completely wrong. But either way, I'd check that out as it is simple and if it is OK, then check out air path to that bank and any vacuum/air take offs specifically to that bank. If all OK, then why not swap coils? See if problem swaps over. If so, you know it is the coil.

The best ideea is to scan your Engine Control Unit with a VAG-COM, Bosch KTS, ... diagnosis tool. If you have one of these dedicated scan tools you will find definitely the engine fault code-"P...." and the clear description of the error. Also you can try to erase this error (or these errors) from the Engine Control Unit memory. If errors are "sporadic" type you certain have permission to erase them, also for some kinds of "static" errors. Because your Engine "MIL" - Malfunction Indicator Lamp keeps coming "ON" and "OFF" you have a big good hand to clean errors from Engine Management System memory. If you don't have any diagnosis tool, you can also try something else. For check up if the engine have a proper turn, you can successively disconnect each spark plug coil from the engine wiring system, engine idle, car stationary. When you operating this you must be free of chassis ground (battery ground)!!! When you disconnect a spark plug coil and the engine speed (rpm) drops, that means this coil works properly. When one coil disconnected and engine speed (rpm) still remain unaltered, this coil (or spark plug) is out of order. First you can change only the spark plug and check up again. If no changes the coil is defective and must be replaced! My recommendation is first to change all spark plugs on the engine, and after that check up coils. Please Rate my Response! Thanks!

440 and 441 relate to the evaporative prurge flow system and 303 is a misfire detectec in cylinder 3.

Finally, fixed the problem. After testing the car with the fuel pressure gage, I found out that the car had proper pressure 46 with regulator and 55 without. After that tested all the voltages on the sensors. They checked fine so I disconnected the spark plugs while running (be careful not to get shocked, it happened to me a couple of times). Found that plug 3 and 6 not getting spark. So i checked the coil. With the car still running I pulled off the wireset at the coil one by one. All checked good except plug 3. That told me that I was not getting any spark from the coil for spark plug 3. I decided to change the coil. However. I also decided to change the wireset because plug 6 wasn't sparking at the plug. After changing coil and wireset, the car is running like a champ. Wish I would have checked it in the first place. It would have save me about $500. I changed out the fuel pump $300. I bought a new fuel filter $10.00. I bought 2 new O2 sensors $100.00 and also I bought a new fuel pressure gage $50.00. Lastly, new coil and wireset $90.00. The car is running like new now. I think better than we we first recieved it. At least I know the fuel pump, O2 sensors are good and now I have a new tool (looking at the positive side). Plus the car is finally fix and running great!!