2004 Ford Thunderbird Q&A
2004 Ford Thunderbird Question: hesitation while accelerating
no codes shown. tps and iacvalve replaced with tuneup. car accelerates ok when not racing to speed. hard acceleration causes hesitation at first. maf and o2sensor not replaced. codes have shown this on my other ford. someone questioned me about the air snorkel??????????? would that be a rare problem? - cadjaw
The air snorkel...also known as the air tube and air filter box -- making sure they are secure and not cracked or broken, as unmetered air getting into the engine can cause issues. However, I don't feel like that is the issue. When you say a tune up was performed -- what in all was done? Did they replace the spark plugs AND the coil boots? You really need to replace those boots during a tune up on this car. Also, the boots should be inspected to determine if there is any oil contamination. The valve cover gaskets on the 3.9L V8 can seep oil into the plug holes and oil soak the rubber coil boots...which deteriorates the boots and causes them to arc under load. Being that your concern is primarily under load, I'm going to suggest you focus on the coil boots first, if they have not been replaced. Any way you look at it -- just do not throw parts at this car! A good diagnostic test is in order, which will be cheaper than making an error in parts. Good luck! - DaveJHM
If you experience difficulty starting the engine when cold, stalling at idle, or hesitations during acceleration, it may be the idle air bypass valve. This valve helps the vehicle idle steady when ...