About 3 weeks ago i started getting missfire codes on my 4.0 TJ. Since that time the problem has gotten worse and now has no power at highway speeds. The code thrown is sometimes is cylinder 2, sometimes 3. in the drive way its fine at any RPM and will rap up with out any problem.
Under Load while driving - It has a slight poor throttle response at low RPM but is mostly fine. At higher RPMs (~2600+) it has low power and kinda just chokes out.
Here is what I have done so far
- I pulled the plugs and checked them they were all fine and were gapped in spec - (autolite double platinums with ~10k on them). I moved them around and the problem stayed the same.
- I replaced the coil pack with an extra I have from an 2005 and have the same problem.
- I replaced the fuel injectors with my spare set of freshly cleaned ones and still have the same problem
The vacuum at idle is 18 in/hg. The gauge doesn't shake or jump although every 30 seconds or so it will cycle down to 17 and back up (might be the AC though). with the engine wrapped up in the drive way the vac is rock solid at any given RMP.
from idle if i open the butterfly and release it the vac dives to about 15 then jumps up to 24-25 as i release it.
I'm gonna go pick up a longer hose and check the VAC under load and see if I see anything and maybe check the compression.