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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

need help badly

 
  #1  
Old 01-06-2011, 01:47 PM
NTimidate3
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need help badly

i have a 89 f 150 witha 302 got good spark but yet i have a misfire on #3 cylinder check compression all cylinder are between 125 -140 psi all plugs and wires are good and getting spark if anyone has any ideas please let me know thanks
 
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Old 01-06-2011, 01:51 PM
van o
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Got fuel at the #3 cylinder. could be a bad injector
 
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Old 01-06-2011, 02:39 PM
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When did this problem occur?

Since there isn't a cylinder balance test for this vehicle, other than shorting the injectors out, what leads you to #3 cylinder not firing correctly?

If you are completely sure that #3 isn't firing correctly, I would check the plug itself. I have heard of the porcelain having a stress crack from overtightening, just from age itself, or if it were hot and water hit that plug, causing a miss. You need to disconnect the plug wire from the plug and check for spark to that cylinder.

Let us know what you find.

Also check that the plug wire itself is GOOD! I have heard on here that plug wires, though new, have been bad out of the box. Check for resistance with no more than 5K. Wiggle the wire to ensure it isn't shorting out.
 
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Old 01-06-2011, 02:44 PM
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don't forget the obvious... check your cap and rotor. I would swap around a plug and wire to see if you still get spark. Is your plug wet with gas? does it smell rich? if so you are getting fuel but it still might not be enough. I'd swap a couple injectors and see if the miss moves cylinders.
 
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Old 01-06-2011, 03:14 PM
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i removed the # 3 plug wire from the cap while it was running and the engine stayed idling the same way verses the the other cylinders made the engine run rougher. i also ohm check the wire and it checks out good
 
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Old 03-01-2011, 11:58 PM
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my truck does the same thing but with cylinder 8. it has spark and new plugs and wires. il take off that wire and it will run the same. injector not firing? i dont know what else it could be
 
  #7  
Old 03-02-2011, 07:22 AM
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I would think it's an injector... Like I suggested before. Swap your #3 and #5 injector and see if the miss moves to #5 with the injector. If it does I suggest getting a set of refurbed and flow matched 19# injectors... You can also go to RJM and get a refurb kit yourself and then do a self clean with a injector wire from the JY. If you want to know how to do the home clean on the injectors let me know...

1992 F150 Fuel Injectors 5.0 302 5.0L 4x4 Rebuilt Set 8 on eBay!
 

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