Troubleshooting lean condition?

[DAA]

So the CEL came on in my '06 Wrangler last weekend. It was running fine and I was a long way from pavement so I ignored it and it went out by itself after a few start cycles between hikes.

Just pulled the codes a few minutes ago. P0171 and P0174 - "System too Lean". On banks 1 and 2.

Since both banks each threw a lean code, I'm just guessing it's not O2 sensors? That it actually was/is running lean.

So... Where to start looking? How to troubleshoot?

My first thought is the collector flanges have come loose. So I'll make sure they are tight.

But, where else, what else should I be checking, looking for? Most common cause for these codes and the remedies?

'06 Wrangler, 4.0, CAI and Edge moduel and TB installed - which I guess might be related, but that stuff has been there for about 4 years now without codes.

Any and all help/advice appreciated!

- DAA

 

[MikeGyver]

I'd start by replacing the fuel filter. If that doesn't fix it check the fuel pumps pressure at the rail. Other things to check for: intake/exhaust leaks, clogged injectors, o2 sensors

 

[rholbrook]

I'd start by looking for a vacume leak. Its cheap and easy to eliminate at first. You can use ether to spray around and listen for the engine to idle higher. Dont spray it around your exhaust manifold. Speaking of the exhaust manifold, could you have a crack starting? That could cause the code too.

 

['03_RUBI]

Look at the freeze frame data for the codes to see what conditions the codes set under, that will help narrow it down.

 

[DAA]

My cheap scan tool doesn't give me freeze frame data, only tells me that it is there. I can tell you that the CEL came on early on the second full day of mild off roading - just putting down rough two tracks at low speeed/low RPM.

Fuel filter... I "think" the only filter on this rig is the one on the pump, in the tank? Not sure about that though. If there is another one, outside the tank, I'll change it just on GP.

Will check for exhaust and intake leaks for sure. Including checking the manifold close, but being an '06, the last year of productiong for the 4.0, I think they finally had that one solved. But maybe not .

Question - could a cat(s) starting to get plugged cause this code, or would that cause the opposite?

Thanks!

- DAA

 

[DAA]

Just thought I'd update since I dicked around with this yesterday.

No exhaust leaks I can detect. Flanges were tight, no cracks, all looks/sounds good.

No vacuum leak I can detect.

There isn't a serviceable fuel filter on this rig - just the strainer on the pump in the tank, so I wasn't able to change it.

And... It appears Mopar in their infinite wisdom removed the shrader from the fuel rail for '06 so I couldn't even buy or borrow a gage and check the fuel pressure.

I wouldn't think clogged injectors, simply because the motor only has 52K on it and I've always used quality gasoline and put a bottle of Techron through it at every oil change. Plus, it runs smooth as silk, no missing, no roughness at all.

And "I" wouldn't think O2 sensors either, but I'm sure I could be wrong. It's just that both banks throwing the code at the same time, would mean both sensors going bad at the same time and that just seems less likely than that they were telling the truth and the rig was actually running lean.

Anyway... No closer to figuring it out at this point. So I cleared the codes and will hope they don't come back. If they do, I guess I'll have to figure out how to measure fuel pressure without a shrader in the rail. Has to be a way?

Still curious what a cat starting to clog would do? Would that throw a lean code or a rich code?

- DAA

 

[Spork]

Still curious what a cat starting to clog would do? Would that throw a lean code or a rich code?

- DAA

On mine it was a P0420 code Catalyst System Efficiency Below Threshold

For your code what does Jeep do for a mass air flow sensor? (is it dirty?) You can buy electronic cleaner spray and clean it. On my truck it's just a small sensor on the intake with some thin wires, pull the sensor, hit it with the electronic cleaner spray and let it dry for a few seconds and stick it back in.

http://www.obd-codes.com/p0174

 

[rholbrook]

Mass Air Flow Sensor would be
Y next suggestion. Clean it but be very careful. My MIL had one a couple of months ago hat needed cleaning and her car hadess than 80k on it. With 50k on the LJ it just seems odd your having issues. Maybe it's just pissed you havent shot enough coyotes lately. Tell Cindy that I ran into Dawn Anderson. Looks and acts the same

 

[DAA]

Good thoughts on the sensor. The 4.0 doesn't have a MAF, it uses MAP, but I'd imagine it would be just as likely to get dirty and start throwing codes. I think if it is too junked up, a new one is pretty cheap too, compared to a MAF.

Sometime this week I'm going to try and pull the OPDA to inspect the oil pump gear and install a zerk to make the top bushing greasable. Will pull the MAP sensor to inspect and hit it with some cleaner while I'm at it.

- DAA

 

[DAA]

Okay, another update...

I did pull the MAP for inspection and it looked spotless to me. So, I cleared the codes and hoped for the best. Drove it a few times around town, just to get the OBDII cycle going, no CEL, ran fine etc.

Did the SRS run with the guys this weekend. Jeep ran great the whole trip, no CEL until right at the very end. While I had it running at about 1700 rpm in neutral airing up my tires, the CEL came on again. This was right at the Goblin Valley turnoff by Temple Mountain. Drove home and again, it seemed to be running fine. In fact, it almost seemed to be running "better" than fine. Seemed like it might have been pulling grades just slightly better than usual. Maybe that's just my imagination, but it ran great, put it that way.

One other small clue on this trip, that has me thinking it isn't just a faulty reading but really is running lean. For the whole trip, about 400 miles of pavement running mostly 70-80 MPH and about 160 miles of dirt, the Jeep averaged a solid 13 MPG. I track my MPG very closely, at every fillup, all the time, just so I can calculate my range in any given situation. The Jeep normally would have averaged 12 MPG for this trip. A 1 MPG increase isn't much, but I'm fairly certain that it's "real". I think even that small increase in MPG would tend to confirm a lean condition?

Anyway... No closer to solving it. But now convinced I do have a lean condition that I'm going to have to get figured out and fixed. Really no idea where to go from here though. Guess I'll start by just disconnecting the Edge module and see what happens. Don't have a lot of faith in that getting me anywhere though, the Edge has been on there for four years and never had any codes.

- DAA