Misfire under light load
#1
Misfire under light load
Hi Guys Here is my Problem....I have an F-150 Lariat 4x4, 3v 5.4, 90,000 miles has a misfire between 45 and 50 miles an hour under light acceleration. Once parked the truck smells of unburnt fuel and the #2 (Left side) Cat smells hot and shows white discoloration, right side Cat is unaffected. The truck has intermittent check engine light and showed a #5 and #8 cylinder misfire. I replaced the COPs on the affected cylinders with no resolve. My question;: is there a reason a misfire would surface at 45-50 MPH and what steps could I take to further troubleshoot the misfire? (note: 3V 5.4 Triton does not have an EGR valve). I would appreciate any help on the subject. Thank You
#2
Mark
iTrader: (1)
What about the plugs for thoses 2 cylinders...90K miles it may be time for plugs.
#3
I am going to change the plugs this weekend. What do you make of the misfire only occurring around 45-50mph? Is there something that the engine does at this speed that would change and cause the misfire?
#4
I had the same problem in the truck that I bought and also noticed the same to varying degrees in most of those that I drove. Changed a few coils which made it a better. Changed the plugs which made it better. Changed the phasers, adjusters, etc., which made it better still. Now with the motor running as it should, I haven't had any more problems. Think that it's probably just a question of getting things right overall whatever that might be in your particular case.
#5
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Join Date: Oct 2010
Location: Virginia Beach, VA
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Your symptom coupled with your mileage are indicative of bad plugs. Change ALL the plugs and you should be fine.
I had the same exact symptom with less miles, and a plug & boot change cured it! If you are going to do it yourself, be prepared in case some break.
I had the same exact symptom with less miles, and a plug & boot change cured it! If you are going to do it yourself, be prepared in case some break.
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#8
I'll start with the plug change and see if new plugs fixes the miss. My Lisle tool just came in the mail today. I am going with the Champion 7989 spark plugs so I wont have to deal with extracting broken plugs again. As for the solvent to soften the carbon build up on the plugs I was going to try Aerokroil. Has anybody use this stuff to loosen there plugs? and it so how good did it work?
#9
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Join Date: Jul 2011
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heres what i did for the carbon problem. took the air filter out and got a funnel with a hose on it to extend inside breather. then i took 3 bottles of the cheap STP injecter cleaner (walmart) and slowly poured them down the engine while revved to about 2000 rpm`s. next i poured a quart of transmission fluid down it. (lots of smoke) drove the truck about 10 miles before i changed the plugs and there was not even a trace of carbon. all 8 plugs came out without a hitch. this is a truck that i bought at an auto auction with 205,000 miles. i have no idea of its service record.
#10
Senior Member
After dumping a quart of tranny oil thru the combustion chamber you probably toasted your cats and o2 sensors. Why in the world would do that.
To the op - what year is the truck. 2005s have know injector problems. At 90k definitely time for a plug change. Use carb cleaner for soaking the plugs. Follow the tsb and you should be good.
To the op - what year is the truck. 2005s have know injector problems. At 90k definitely time for a plug change. Use carb cleaner for soaking the plugs. Follow the tsb and you should be good.