Desperatly need help with a P0303 and P0305 code.

SKILLEDHANDS2

MEMBER
1996 FORD RANGER
300,000 MILES

I am working on a 1996 ford ranger with a 3.0L(vin U) with 300,000miles. My issue started with a P0306. 4 months prior I had replaced all plugs, wires, coil pack and had both cylinder heads rebuilt at a machine shop. I narrowed down my problem to a faulty injector. Replaced all 6 injectors with new factory injectors and now I have a p0303 and p0305 codes. This started right after replacing injectors. Swapped injectors from 3 and 5 to 1 and 2 and still have the same codes. I have checked vacuum and I have 15 at idle. I have 150psi compression in all cylinders and all plugs look normal. KOEO I have 40psi fuel pressure. At idle it misfires really bad and my LT fuel trim is 18% on bank 1 only. While driving it goes down to normal. Bank2 fuel trims seem normal. I have even blocked off the EGR port and it didnt change. I have run out of ideas on whats causing my issue. Please email me if you watn further info. I am a ASE certified tech that has run out of ideas to fix this issue. Any help would be greatly appreciated.

5 Replies

KHLOW2008

CERTIFIED MECHANIC
41,816 POSTS

Under such circumstances, get back to the basics. Recheck the spark plug, ignition coils and wires. New components might be faulty.

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Saturday, October 15th, 2011 AT 8:39 PM

SKILLEDHANDS2

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3 POSTS

I have checked and rechecked all new components. Only new components were the injectors. Swapping them did not change the misfire condition. I know it has to have something to due with the fuel trim levels being so bad on bank 1 but I am not seeing an issue that would cause it. I have replaced all rubber vacuum lines and my gauge is reading steady vacuum of 15 at idle.

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Monday, October 17th, 2011 AT 2:35 PM

KHLOW2008

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You mentioned replacing the spark plug, wires and coil packs. Were they rechecked?

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Monday, October 17th, 2011 AT 4:36 PM

SKILLEDHANDS2

MEMBER
3 POSTS

I have rechecked parts and swapped plugs from 3 and 5 to 1 and 2. I still am leaning towards some type of vacuum leak due to the fuel trim issue but my gauge is steady at 15 at idle. Engine smooths out will driving. Everytime I touch this truck it turns into a headache.

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Monday, October 17th, 2011 AT 4:45 PM

KHLOW2008

CERTIFIED MECHANIC
41,816 POSTS

Misfiring at low rpms would not be noticeable when the rpm increases or load decreases. The most common causes of misfirings are spark plug wires rather than spark plugs.