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  #1  
Old 01-29-2009, 10:08 PM
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Location: Virginia
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Smile '97 F150 engine miss and spark knock

I have a '97 F150 with 4.6 V8, automatic transmission, 4x4. The truck was not used for approximately 1 year prior to me purchasing it. When I first purchased the truck it had a slight spark knock during acceleration, slight miss that seamed to clear up and would die when you came to a stop after driving when it was at operating temperature, unless the AC was on. But it was drivable.
Then it would sometimes exhibit a no start condition until it was cranked for several minutes. When it did start it would run really rough,like it had a miss fire or vacuum leak, but would clear up and run okay.
Now it runs rough anytime you start it up, seams like a bad misfire. It can be driven, however you can not accelerate fast or it sounds like it has major spark knock. I have replaced the sparkplugs with autolite platinums, new plug wires, removed the throttle body and spacer and cleaned the carbon deposits from them. Also cleaned the IAC. Also during the whole ordeal there has been no check engine light.
I have read many threads that point at a large range of possibilities but all of the threads have noted a CEL was on. As I have pointed out, I have no CEL on. This could be due to the truck not being driven for very many miles. Trying to avoid the high cost of taking to the dealer, but I am at my wits end for what the cause could be. Any help would be greatly appreciated.
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Old 01-30-2009, 08:37 PM
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Try checking the timing and run Seafoam in the tank.
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  #3  
Old 01-30-2009, 09:03 PM
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Currently I have Lucas fuel treatment in the tank. Unfortunately, I am not sure how to check the timing on any vehicles with electronic ignition. Can you give me a little insite or place to go for information.
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Old 01-30-2009, 10:17 PM
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Ha. Sorry, I was thinking of earlier trucks.
Did you check/change the plugs at any time.
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Old 01-31-2009, 04:17 PM
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Tup. Brand new plugs. Less then 30 miles on them. Changed the plug wires after the plugs. Pulled all the plugs at that time and checked them. The number 4 cylinder was sooted up. It looked like unburnt gas not oil. I am thinking the injector may be bad or partially blocked. Have not been able to get to autozone to get a noid light to test the injector operation.
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Old 01-31-2009, 05:03 PM
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If the plug has raw fuel on it, it is possible the injector is hung open dumping fuel. If it is wet with fuel, the injector is not plugged. It is awkward, but you can pull the fuel rail up with injectors in the rail and see if any are dripping.
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Old 02-01-2009, 10:27 AM
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You can also switch the injectors to different positions to see if the same happens on that position.
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Old 02-01-2009, 10:27 AM
 
 
 
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150, 1990, 1994, 2006, 46, 97, engine, escort, f150, ford, gt, knock, miss, motor, rail, repair, spark

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