jerry

Had my 01 that I just purchased start misfiring on me the other day and posted a question about it. After trying to figure it out myself I finally just took in in to the dealer. They flushed my injectors for me and told me it was fine the first day because it wouldnt misfire for them. I told them it had to sit running for a while and get hot but they didnt believe me. Before I got it home in 5 o'clock traffic it did it again. I turned it around and brought it back. They just called me and said they moved the #3 to #2 position and the computer gave a misfire #2 code. Same when they moved it to #1 spot. So its definately a bad #3 injector. Heres my question- why do so many #3 injectors that I read about on this forum go out? Is it a bad design of the intake where they sit(picking up too much heat ?) And if it is it seems to me shielding it with a plug boot would make the heat prob. worse since it is likely not radiant heat otherwise all the inj. would misfire. Can anyone shed some light ?

funkle95xj

The 4.0, especially in the xj, is well known for this. It is caused by the #3 injector being located extremely close to one of the exhaust manifold pipes. In this area, it is exposed to alot of heat soak. This can lead to the fuel inside the injector vaporizing, leading to a misfire condition due to a temporary lack of liquid fuel flow. Obviously being exposed to higher than normal heat can lead to premature failure of the injector as well. I'm sure having to deal with this vaporized fuel condition isn't exactly easy on the injector either.. A good way to counter this and prevent it from happening is to get some of that quality heatsheild tape (available at most auto parts stores) and wrap each injector with it, like a mini heat shield. This can help lower the temperature enough to stop, or at least minimize this condition.
HTH!!

jerry

thanks my friend, I'll try it !