hesitation and idle issue.
Hello jf, I know this has been discussed before, but I haven't found many final answers to this issue. The jeep is a 98 wrangler 4.0 liter This problem happens when the jeep is hot or cold. The jeep takes three or more attempts cranking for it to start, which I will assume is the fuel pressure check valve. Then at around 2000 rpms it hesitates, backfires, and loses rpms unless I push in the clutch and give it enough gas to hit 3000 rpms. Then it will be fine for a second, then repeat over and over through every gear until I stop, at which point the idle drops down to 500 rpms or less, sometimes stalling. There is a strong smell of unburnt fuel in the exhaust, and it backfires on a downshift. Now to what I have done, replaced the downstream oxygen sensor after code p0138 was thrown, fuel injectors cleaned, IAC cleaned, TPS cleaned, TB cleaned. My last couple of suspicions are CPS and fuel pump. I haven't checked fuel rail pressure as I do jot have a fuel pressure gauge. I am stumped, not sure what I should do next.