P0303 code misfire on #3
Freshman User
Joined: Dec 2013
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Here’s what i know. When looking into a misfire condition think F.A.F. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com
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Test the fuel pressure. If you have is it with in specs<o></o>
Test for proper vacuum. If you have done this is it with in specs<o></o>
Test the compression on the coded cylinder (wet and dry) and the one next to it. The results of the compression test should be within 25% of each other.<o></o>
If the compression fails. Do a leak down test. I modified an old compression testing tube by removing the small value in the end. Doing this allows me to introduce compressed air into the cylinder. in order for this type of leak down test to produce results the engine / cylinder needs to be at top dead center of the compression stroke ( this closes both the intake and exhaust values and what you end up with is a sealed chamber. Now you introduce the air. While you’re putting the air into cylinder you need to listen to four locations one at a time. First the coolants: if you see bubbles in the coolant then you have a head gasket issue. Second the tail pipe, if you here air here the you got a stuck exhaust value. Third the throttle body if you here air here your intake value is stuck. Fourth location is the value cover listen for air coming from the same location you put your oil in. if you here it there then you got a ring or a small cracked piston. When I try to resolve a misfire code. These are the first things I do. It helps me pin point a system. If your fire pit (aka combustion chamber) is sealed. And you have good fuel pressure. Then the problem is with the ignition.<o></o>
fficeffice" /><o></o>Test the fuel pressure. If you have is it with in specs<o
></o>Test for proper vacuum. If you have done this is it with in specs<o
></o>Test the compression on the coded cylinder (wet and dry) and the one next to it. The results of the compression test should be within 25% of each other.<o
></o>If the compression fails. Do a leak down test. I modified an old compression testing tube by removing the small value in the end. Doing this allows me to introduce compressed air into the cylinder. in order for this type of leak down test to produce results the engine / cylinder needs to be at top dead center of the compression stroke ( this closes both the intake and exhaust values and what you end up with is a sealed chamber. Now you introduce the air. While you’re putting the air into cylinder you need to listen to four locations one at a time. First the coolants: if you see bubbles in the coolant then you have a head gasket issue. Second the tail pipe, if you here air here the you got a stuck exhaust value. Third the throttle body if you here air here your intake value is stuck. Fourth location is the value cover listen for air coming from the same location you put your oil in. if you here it there then you got a ring or a small cracked piston. When I try to resolve a misfire code. These are the first things I do. It helps me pin point a system. If your fire pit (aka combustion chamber) is sealed. And you have good fuel pressure. Then the problem is with the ignition.<o
></o>
Thread Starter
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Mountain Pass
Joined: Nov 2012
Posts: 112
Likes: 11
From: Hurst,Texas
After a trip to Ford it was a simple fix they put it on their scanner which does more than mine and found a hard miss on cylinder #2 tech installed his test plug and it fixed the miss. All this crap and it ended up being fouled plugs due to fuel additives which I add about every 10 or 15 fill ups so their tech told me to STOP adding the fuel additive OKAY so maybe this is it sound kinda of far fetched but what the hell I have nothing to loose at this point. So changed the plugs out got my money back from orielly's auto because the plugs had less that 6 months on them Manager was great about giving me my money back so after all that I was out the diagnose fee that Ford charged $90 and my labor so far it's been running fine for about 3 weeks with no issues just filled up with premium gas for this tank see if I can burn some of the crap out of the cylinders. I'll keep posting on progress and let see if this fixes it.
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