Hey Guys, got a 2004 Wrangler Unlimited with 4.0. Have had a check engine light for both the P0172 & P0175 codes detecting the engine is running too rich. I have replaced fuel pump, fuel injectors, IAC Valve, MAP Sensor, Throttle Position Sensor, and all the O2 Sensors when I put the new catback exhaust in. This code has been around since before any of these new parts and I just cant seem to get the the bottom of it. Also has a rough idle when its cold as well. Any suggestions or ideas would be greatly appreciated.
Engine Running Rich
- Thread starter Kwanderson2004
- Start date
What brand O2 sensors did you install, Bosch or NTK. Is your temperature gauge registering the normal 210 degrees or close while you're driving?
All Proper NTK Sensors upstream and downstream, engine temp is well within normal operating range.
New IAT went in just fine, cleared the code and it came back within ten minutes of driving. Running out of ideas that are causing these codes at this point.
John Scoggins
TJ Enthusiast
What is the condition of the ignition system? Have you checked the fuel pressure to see if it is running to high (above 58PSI)? Check for a restriction in the intake system, including the air filter.
Since you have changed both O2 sensors, have you checked to make sure the signal circuit is not open (maybe from wiring harness damage) or shorted to voltage?
If you have an OBD tool that can look at the PID's real time, check the O2 PID voltage signal to make sure it is sending a good signal (the signal should float around a bit)
Since you have changed both O2 sensors, have you checked to make sure the signal circuit is not open (maybe from wiring harness damage) or shorted to voltage?
If you have an OBD tool that can look at the PID's real time, check the O2 PID voltage signal to make sure it is sending a good signal (the signal should float around a bit)
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Yep, time to check live data.
I'm beginning to suspect broken or damaged wiring, somewhere.
However, since this thread popped up right near a PCM thread, have you swapped out PCM's (with a friend's) to see if the problem remains?
I'm beginning to suspect broken or damaged wiring, somewhere.
However, since this thread popped up right near a PCM thread, have you swapped out PCM's (with a friend's) to see if the problem remains?
Vacuum leaks can cause these codes. Your cold rough idle also could be caused by vacuum leaks that go away after vacuum line rubber expands after the engine heats up to operating temperature.
Ignition coil is new, what voltage should I be getting from O2 circuit if I check it?
Is there a engine/exhaust tick? My cracked exhaust manifold fooled with my o2 sensor causing fuel delivery issues.
swampy@06LJ
New Member
Curious if there’s been any progress or solution to this? I’m battling what sounds like a very similar situation. 06 LJ, I bought it at the end of April, the CEL was on, P0172 and P0175 codes. It was a very clean LJ, just had some things neglected on it. I installed a S&B CAI, Reman Bosch 6 hole injectors, replaced the IAT sensor, MAP sensor, both upstream O2 sensors (with proper NTK), among many other little odds and ends. I thought I had it, made it 2 different ~15 minute drive cycles. Took my wife and son for another test drive for an ice cream cone since they’ve been so patient with me and the new Jeep. After ice cream, the dang CEL comes back on with the same codes... I don’t have immediate access to a DRB, my buddy has one about 90 minutes up the road.
My O2 sensor codes were ultimately cured by replacing the precats. With the new precats the old O2 sensors were reinstalled. No O2 codes or misfires in the 8-9 years since Blaine replaced all three of the cats for me. One precat disintegrated on the way home from a wheeling trip. Its internals were blown downstream where they plugged the main catalytic converter which suddenly took me from 65 to 5 mph max on the highway.
swampy@06LJ
New Member
Thanks Jerry! My Jeep does have what sounds like a heat shield rattle that I can’t seem to pinpoint, but it was also lower on the priority list. I pounded on the pre cat with my fist, not a significant noise but Bank 2 had a little bit of a noise. It’s got 156K miles so I think it’s feasible this could be a real possibility. The previous owner had the #6 valve spring break and a repair shop fixed it about a month before I bought it. I’m wondering if there was a potential back pressure issue. There was a recent exhaust repair too... might be on to something here. Also, I want to let you know I read your review on the PRP Daily Driver seats and I ordered them a few weeks ago. I’m hoping they show up in the next few days. I’ll update this thread with my findings.