Is there any new insight on this? I too have had this code pop up occasionally and as of yet been able to find an exact situation that might cause it. I have suspected an exhaust leak but the code doesn't pop up frequently enough to support this. To be fair, even though this is my primary vehicle I barely get 6000 miles a year on it. Time wise I can go 6 plus months of the code not coming on but then get it 3 or 4 times in a single month. I know this motor isn't a power house but I'm wondering if this could be why the jeep seems to fall flat on its face past 3200 rpm even with the upgrades I have added.
Fuel pressure testing?
- Thread starter DAA
- Start date
DAA
Well-Known Member
- Location
- West Bountiful, UT
I'd test your fuel pressure. Mine was, is, running fine. I did feel like it had more top end after the pump swap, but, like you said, it's kind of hard to tell 
.
Regardless, something wasn't right with the old module. With the new one, this is what I see with key on, engine off, what I see at idle, and what I see with the throttle opened up. Picture is with the throttle open. Needle is much more steady under throttle, too. It takes a dip, then comes right back and sits pretty solid. It used to bounce a lot, wherever it was, with the old one.
Buuuuttt.... But, but, but... My code came back. Along with a very small evap leak, but that is basically normal for this rig.
So, fuel was on it's way to becoming a real issue and I'm glad I swapped out the module before it bit me at a bad time. But I still need to figure out what is throwing the code. Haven't had time to mess with it yet. Going to look harder for an exhaust leak first, starting by simply making sure the flange and manifold bolts are all tight. Then look harder for a vacuum leak (good excuse to score a cheap smoke tester). Then I'll go to sensors, starting with the MAP (I don't really suspect the 02s, but....).
- DAA
.Regardless, something wasn't right with the old module. With the new one, this is what I see with key on, engine off, what I see at idle, and what I see with the throttle opened up. Picture is with the throttle open. Needle is much more steady under throttle, too. It takes a dip, then comes right back and sits pretty solid. It used to bounce a lot, wherever it was, with the old one.
Buuuuttt.... But, but, but... My code came back
. Along with a very small evap leak, but that is basically normal for this rig.So, fuel was on it's way to becoming a real issue and I'm glad I swapped out the module before it bit me at a bad time. But I still need to figure out what is throwing the code. Haven't had time to mess with it yet. Going to look harder for an exhaust leak first, starting by simply making sure the flange and manifold bolts are all tight. Then look harder for a vacuum leak (good excuse to score a cheap smoke tester). Then I'll go to sensors, starting with the MAP (I don't really suspect the 02s, but....).
- DAA
Last edited:
- Location
- Vehicular limbo
There's only one way to fix this, really. Dave needs a Bronco.
- Location
- Bountiful, land of rocks
LS swap that gal
Lol. I too get a random 456 code. Funniest thing for me is I usually get these codes right before emissions are needed. Always gives me a chuckle. I probably shouldn't ignore it but it's been literal years of these codes randomly popping up and going away either by force (tuner) or on their Own. The longest i have had a code was a week or two. I personally don't have the patience to trace random codes. I will keep following whatever you post about this
DAA
Well-Known Member
- Location
- West Bountiful, UT
Minor, inconclusive update...
I ordered a cheap smoke tester from Amazon. Fun little unit, glad I have it now. It found two vacuum leaks I didn't find spraying flammable brake cleaner and carb cleaner. One of them, where the PCV goes into the intake manifold, I couldn't believe the flammable spray hadn't shown it - it's a decent leak in the most obvious place. So I tried spraying that spot again with the engine running, and yeah, now that I know it is there, the change in running is faintly detectable. The other vacuum leak, on the tiny elbow pipe from the MAP sensor to the TB, even knowing it's there because of the smoke, I couldn't tell anything spraying it with the engine idling.
I want to use factory parts and didn't want to mess with LHM Bountiful, so I ordered them online but they haven't shipped yet. Might clear up my lean code, maybe. Just have to wait till the stuff gets here and see.
I decided to put the smoke machine to use looking for my very small evap leak, which I had a strong suspicion was coming from a pipe connection to the leak detection pump and evap cannister, that had to be disturbed while changing out the fuel pump. That wasn't it though. It was a pinhole in a vapor line on the other side of the tank where I think it got pinched on reinstalling the tank for the new fuel pump. I'd have NEVER found that leak without the smoke.
It was luckily in a spot on the outboard side of the top of the tank that I could kind of reach by unbolting the shocks and drooping out the rear axle to get it out of the way. Without dropping the tank. I cleaned up the section of vapor pipe with acetone and put a good wrap of electrical tape on it as best I could. Still just a tiny bit of smoke escaping - but way less than before. So I hosed the new tape down with hairspray, let it dry, put another layer of tape on, hosed that down with hairspray. I can't see any smoke coming out anymore. The repair may not last, or maybe it will, but I think it will last long enough to clear that evap code and I know exactly where the leak is now if and when it comes back.
- DAA
I ordered a cheap smoke tester from Amazon. Fun little unit, glad I have it now. It found two vacuum leaks I didn't find spraying flammable brake cleaner and carb cleaner. One of them, where the PCV goes into the intake manifold, I couldn't believe the flammable spray hadn't shown it - it's a decent leak in the most obvious place. So I tried spraying that spot again with the engine running, and yeah, now that I know it is there, the change in running is faintly detectable. The other vacuum leak, on the tiny elbow pipe from the MAP sensor to the TB, even knowing it's there because of the smoke, I couldn't tell anything spraying it with the engine idling.
I want to use factory parts and didn't want to mess with LHM Bountiful, so I ordered them online but they haven't shipped yet. Might clear up my lean code, maybe. Just have to wait till the stuff gets here and see.
I decided to put the smoke machine to use looking for my very small evap leak, which I had a strong suspicion was coming from a pipe connection to the leak detection pump and evap cannister, that had to be disturbed while changing out the fuel pump. That wasn't it though. It was a pinhole in a vapor line on the other side of the tank where I think it got pinched on reinstalling the tank for the new fuel pump. I'd have NEVER found that leak without the smoke.
It was luckily in a spot on the outboard side of the top of the tank that I could kind of reach by unbolting the shocks and drooping out the rear axle to get it out of the way. Without dropping the tank. I cleaned up the section of vapor pipe with acetone and put a good wrap of electrical tape on it as best I could. Still just a tiny bit of smoke escaping - but way less than before. So I hosed the new tape down with hairspray, let it dry, put another layer of tape on, hosed that down with hairspray. I can't see any smoke coming out anymore. The repair may not last, or maybe it will, but I think it will last long enough to clear that evap code and I know exactly where the leak is now if and when it comes back.
- DAA
- Location
- West Haven, UT
Do you mind sharing the make/model of the smoke machine. I've had an on/off Evap code for 10 years in my TJ
DAA
Well-Known Member
- Location
- West Bountiful, UT
DAA
Well-Known Member
- Location
- West Bountiful, UT
And you are welcome to borrow mine for a couple days if you'd like. I think I'm done using it for now.
- DAA
- Location
- West Haven, UT
Might take you up on it.
DAA
Well-Known Member
- Location
- West Bountiful, UT
Fixed the vacuum leaks yesterday. Both the P0171 and P0456 have cleared themselves and the CEL not lit anymore today.
Win.
- DAA
Win.
- DAA