I have a 2004 laredo 4.0 inline six. It recently developed a dead miss in cylinder four and indicated the throttle position sensor was bad. I replaced this and saw no improvement in the misfire. The misfire got way worse the engine started loping and the engine light started flashing. I changed the oil and added lucas oil treatment due to an unrelated tick in the engine. I used seafoam prior to the oil change in crank case air intake and fuel tank with a fresh tank of midgrade gas. I changed the coil pack and plugs with autolite plugs which is what the book called for. Now I have a misfire in cylinder four and six. The engine runs quieter but misses just as badly. I admit i did not read the code once the engine light started flashing so the misfire in cylinder six was most likely already present. I should note i purchased all parts from NAPA and opted for the more expensive coil. I need to know if there is another module on the vehicle that is responsible for regulation of the current to the coil. Or if an air fuel mix could be responsible? My mind is all over the place on this with everything from the 02 sensor banks to the fuel injectors themselves but this seems like a fire not fuel issue. Any thoughts?

 

Take it to a shop. You will save money in the long run. A throttle position sensor will not cause a single cylinder misfire.

 

Will a bad lifter...?

 

There are only 2 things that will cause a misfire in one cylinder consistantly, a bad or shorted plug or an injector not injecting. THAT could be caused by being plugged with crap or not opening due to electrical causes.

 

And loss of compression.

 

If compression is good im going to change out plugs and move the fuel injectors around to see if the miss follows. Thanks for the advice.