I picked this car up right towards the end of winter. There was an odd, sudden dip in the idle at the time but it wasn't all that bad and the price was right (famous last words). Anyway it starts fine with a solid tact but after a few minutes the tact starts to vary. Eventually it's misfiring so bad that you can't even touch the gas pedal without it bogging like it's flooding out. Seems worse when it's humid and/or when the car runs for a while. No engine light. Except once and that cleared on it's own. And right now it's not pulling any engine codes. Replaced cap, rotor, spark plug wires, spark plugs, and cleaned the fuel system. Still does the exact same thing. Anyone have any idea what's wrong? Mechanic charged me $820 for the work so far but being a fairly reputable dealer refunded everything! Any thoughts? Any common issues with this car I should be aware of?

 

Welcome to DF
If its misfiring, you should be getting a code. One of the problems with misfires is the valve leaking oil in the spark plug tubes. But there could be others like a crank sensor, o2 sensors, and EGR circuit.

 

Thanks MT. The place I took it to assures me there are no codes. Even I've only seen the engine light come on once. Fuel Delivery then? Or would that throw codes too? I'm grateful that the shop refunded my money but I'm left wondering about their ability to diagnose. Shouldn't these parts be testable? Not just replacing parts until we find the right one?

 

Another thing. It runs fine for the first 10 minutes then gets progressively worse until you can't touch the gas pedal at all. Interestingly though if I manually move the throttle very slowly I can get it to higher RPM's. Quick movements though and it bogs. Throttle position sensor heating up maybe?

 

how did you clean the fuel system?,does throttle body look clean when you look inside,could be sensor but that should turn on engine light

 

Hello BillS. I initially cleaned the throttle body just by spraying it and wiping it down hoping it would help. The mechanic did a more thorough cleaning but I'm not sure what was involved. Based on your comment I unplugged the throttle position sensor to see if I'd get an engine light. I have one now. So I think that rules out that sensor. It also means that the engine light is working lol. It narrows down the question too. What would cause the 2.5L V6 to hesitate so badly that you can't even touch the pedal while also not turning the check engine light on?