need help with misfire codes
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Lead Driver
Joined: Apr 2001
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From: Midwest
need help with misfire codes
2004 4.6 140,000 miles. Here are the codes PO 300,302,303,316. Engine runs great and no check engine light until under heavy throttle. Then check engine light comes on and engine misses. Just had a new cat put on passenger's side for this problem. Thought it was fixed,but it's back again. Really don't want to clog another cat. How can I determine if it's the coils on cylinders 2 and 3 or something else? Really don't want to throw coils on if it's something else.
Hotshot
Joined: Jul 2005
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when you have the coils off, inspect the boot for damage, cracks, carbon tracks.. and make sure the spring is stretched out enough to the end of the boot to get good contact on the plug when installed..wipe off the boot of any oil / moisture/ dirt... blow out the hole around plug with air to get and water or oil out that could cause a short.
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Lead Driver
Joined: Apr 2001
Posts: 6,335
Likes: 6
From: Midwest
when you have the coils off, inspect the boot for damage, cracks, carbon tracks.. and make sure the spring is stretched out enough to the end of the boot to get good contact on the plug when installed..wipe off the boot of any oil / moisture/ dirt... blow out the hole around plug with air to get and water or oil out that could cause a short.
Hotshot
Joined: Jul 2005
Posts: 11,931
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take the coils off 2 and 3 and switch with 6 and 7 ( or other) and rerun the test.
this will tell you the coils are BAD if the code moves to #6 and 7..
If the code stays at #2 and 3, then the electrical plug is bad... or INJECTORS are the problem.
this will tell you the coils are BAD if the code moves to #6 and 7..
If the code stays at #2 and 3, then the electrical plug is bad... or INJECTORS are the problem.
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Lead Driver
Joined: Apr 2001
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From: Midwest
Thought I replied to this but don't see my reply. Swapped coils and codes came back to the same cylinders. would spark plugs do this? Not sure if they have been replaced. 140,000 miles on the explorer. How hard to swap injectors? Would have to release fuel pressure,right? How hard is that with no schrader valve?
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Logistics Pro
Joined: Jun 2009
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From: Cedar Rapids, IA
You shouldn't rule out the camshaft position sensor for the random misfire code either. I'd start by changing out the spark plugs though if you don't know how long they've been in the 140k mile engine.
-Rod
-Rod
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Lead Driver
Joined: Apr 2001
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From: Midwest
UPDATE: here's what's going on now. I replaced the coils and plugs on cylinders 2 and 3. Plugs looked really good and were still gapped correctly. Drove it for 15 minutes. Runs fine at normal acceleration. Hammer it and check engine light comes on and now get codes 300 and 301. Replaced #1 with a known good coil,drove it again,same codes. what next? codes seem to be moving around.
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Lead Driver
Joined: Apr 2001
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From: Midwest
Yes,only po300 and po301 now. Haven't had po316 since I first made this post.
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