Question about Cars & Trucks
Running code scan get PO 303, misfire on cylinder 3, have checked coil pack and replaced spark plug wire, need possible other problems and checks to diagnose the problem.
The code means that cylinder had no power at some point in time.
The most common reason is a faulty spark plug, but it could also be a faulty injector or low compression.
If you know the plug has spark, the next things to check are compression and fuel.
Posted on Jan 07, 2013
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Posted on Jan 02, 2017
It could be carbon deposits on valve seats keeping valves from totally closing. You can try getting you a can of motorcraft PM3 top end engine cleaner and get engine up to operating temp then remove one of the small vacuum lines from the intake and draw the contents of the can slowly into the engine.After you have drawn in the contents shut engine off and let it soak for about 45 minutes then crank it back up and let it run until it clears. Now it will smoke like a forrest fire while you are doing this so don't be alarmed,just tell the neighbors you are spraying for mosqitos.This may cure the problem. If not you may be looking at a valve job.
This can be verified with a compression test if this is what is causing it.
Posted on Feb 05, 2009
Had the same problem, car was misfiring on cylinder 3 and 4. replaced wires, plugs, and ignition coil. still misfired on the same cynlinders. turned out the main engine wiring harness plug in was coming loose. spent well over $150 on the unneccesary repairs and ultimately fixed the problem wit a $3 bag of wire ties to hold the plug in...
Posted on Jun 01, 2009
I beleive your firing order is 1 3 4 2. 1 and 4 are companion cylinders-meaning the piston is up or down at the same time i.e. compression and exhaust stroke both pistons are up and even on the exhaust stroke the ignition fires in order to burn unburnt fuel/ h ve you checked your trigger. There is a good coil testing tool that is placed over the coil and has a magnetic pickup that allows you to see if the coil is being triggered-just because you have power doesn't mean that you will have spark. I would replace your ignition wires and look at your wiring harness very carefully- if it is very brittle and you see bare wires exposed that is your most likley problem because the trigger is working for 1 and 3 and has the crank senser input for all for spark plugs and the cam senser is used for ignition advance and your fuel injection system. try wiggling your harness and see if your coils start to work. wireharnesses are a major problem on mercedes benz vehicles of that era. I hope I have been helpful
Posted on Jun 18, 2009
SOURCE: 2004 Audi A4 misfire
it is always a good idea to stay with o.e.m parts and yes there is updated parts in the newer coils. and yes the M.A.F will also cause misfire faults but will not make check engine light flash or make car shake and shudder. also check you wire harness going to your coils make sure your ground wires are not cracked. That could be the main culprate. good luck hope this helps
Posted on Sep 03, 2009
Tips for a great answer:
Jul 04, 2015 | Cars & Trucks
Sep 26, 2014 | Cars & Trucks
Jan 20, 2013 | 2002 Mercury Sable
Jan 14, 2012 | 1996 Ford Explorer
A code P0303 may mean that one or more of the following has happened:
Feb 18, 2011 | 2001 Jeep Grand Cherokee
Jul 08, 2010 | Cars & Trucks
May 11, 2010 | 1996 Plymouth Grand Voyager
Feb 15, 2010 | 2004 GMC Envoy
Nov 21, 2009 | Ford F-150 Cars & Trucks
Aug 30, 2009 | 2000 Ford Mustang
102 people viewed this question
Usually answered in minutes!