p0174 p0304

Question

I'm working on a 2005 Freestyle 3.0L. As the engine warms up, it develops a lean misfire. Starts,idles and runs good until it warms up. I watched the LTFT 1 and 2 ans saw the number 2 bank is bias lean. The egr module, number 4 injector, spark plugs, fuel filter and O2 sensors are new. None of these ever made any improvements. I did a smoke test on the intake manifold, no leaks. I can disconnect the the number 4 coil while running....still has a misfire. I swapped the coil and plug from number 4 to number 5 cylinder to see if the misfire jumps...it did not. If I slowly press on the gas in drive, it keeps having a misfire until about 1600 rpm then it suddenly hits on all 6 cylinders. Take my foot off the gas, and it returns to idle with the misfire. Did not find any TSB's that apply to this either. So, if anything jumps out at you, I would greatly appreciate the help at this time!.Thank you!

Answer 1

I have almost the exact same problem. Only with me it's cylinder #6. Have you found the problem? Would you mind sharing if you did?

Answer 2

This misfire is caused by the valve seat. You can do a running compression test and it will be confirmed.