MAF codes, EVAP codes, stalling motor, oh my.

MM3846

Well-known member
Feb 18, 2014
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161
LI, NY
This is going to be a long one, so bear with me. 2013 LR4 V8, 70k miles.

Starting last summer, I started having issues filling the truck with fuel. It was random, and was just the pump clicking off very early here and there. I noticed the fuel pump cover was leaking and replaced it (I'm going to the dealer in two weeks to have it done again under the recall). I'm not sure when exactly the fueling issues got worse, but it got to the point where I was struggling to get any fuel in the truck without it getting spit back out from below the filler neck somewhere. I replaced the DMTL pump and purge valve (based on what I was sure was causing those issues, as well as the codes the truck was throwing), and that fixed the fueling up issues.

The next issue I'm not sure when it started, but the truck would stumble and sometimes mis-shift and/or stall after filling up. I thought it was a trans issue, so I changed the fluid and filter and replaced the pan with a two-piece aftermarket one, and reset the TCU with the GAP tool. I still had the fumbling issues but the trans issue stopped happening as frequently when combined with the stumbling. This was ONLY after filing the truck with fuel, and the mis-shift would ONLY happen once. So to me, it was obviously electronic and not an issue with the transmission. It shifts fine every other time. After restarting the truck, or after that first mis-shift, the truck drove completely normal.

I dealt with this for a bit, and then it went away in the warmer weather. It started again a couple weeks ago, I got a MAF code (dont recall which) and cleaned both sensors. The truck was very hard to start one afternoon, but once it did it cleared itself up and drove normally. I got a fuel tank cap warning and replaced with an aftermarket one. That light still comes up every now and then. I cleaned the MAFs again and put in fresh air filters (it threw a MAF code) and that issue went away for a bit. Driving to work I got a reduced engine performance light.

Here are some live value shots from around that time, GAP tach in the upper right is not correct

idle

1665152785516.png

2500rpm in park
1665152824132.png

2000rpm highway cruising at 70mph
1665152860701.png

The day or so after I took those, the truck randomly stalled at a light. Restarted no problem after. I posted on another forum and was told to look for an air leak, not vacuum leak, and I heard one near the PCV valves, but couldn't feel it. But those are cheap enough so I bought them will put in tomorrow.

It's been driving fine, but this morning again I fueled up and the truck stalled out at a red light a few hundred yards down the road. I restarted it and it was still idling a little rough. No codes but the p0442 I've been getting on and off for a year. so some more values:


idle
hATgVrql.png


3/4-ish throttle, pulling 3k rpm ~50-5
M4leurdl.png


1700rpm or so, cruising after the pull
FK1coutl.png


any ideas from the resident pros? My only idea is a saturated EVAP canister could make for a rich condition, but I'm not well versed enough in this stuff to know more than that.
 
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discostew

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Sep 14, 2010
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Northern Illinois
For your fuel trim you need to smoke test it but a good guess if you don’t have access to a smoke machine is the PCV breather diaphragms in the right valve cover. Make sure all the breather tubes from the valve cover up to your fresh air inlet are fully seated.
I’ve seen a lot of strange vac leaks on these. Like the vac pipe to the brake booster disconnected totally at the vacuum pump( lower front of engine) that cars brakes were fine, fuel trim looked like yours.
 
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discostew

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Sep 14, 2010
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Northern Illinois
As far as not accepting fuel sometimes and running like shit after you fill it. I would bet money the purge valve is stuck open. When you fill the tank those vapors should go into your charcoal canister. When the purge valve is stuck open the path of least resistance is into your intake manifold. Then when you start it it’s flooded for a little while.
Actually I would start with a purge valve cause it could cause your fuel trim to go lean also.
 
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MM3846

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Feb 18, 2014
1,221
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LI, NY
Thanks. Purge valve is a little over a year old, but I've gotten bad OEM parts before with other stuff. My buddy has a smoke tester, I'll have to get over there and check it out. I have the PCVs in a box in my garage too, so those will go in tomorrow. I heard the DMTL pump clicking the other day after I parked the truck at home, not sure if that means much or if it supposed to run with the truck off. I'll give the truck a good once over and look for that vacuum pump line.
 

discostew

Well-known member
Sep 14, 2010
7,706
1,015
Northern Illinois
Thanks. Purge valve is a little over a year old, but I've gotten bad OEM parts before with other stuff. My buddy has a smoke tester, I'll have to get over there and check it out. I have the PCVs in a box in my garage too, so those will go in tomorrow. I heard the DMTL pump clicking the other day after I parked the truck at home, not sure if that means much or if it supposed to run with the truck off. I'll give the truck a good once over and look for that vacuum pump line.
If this purge valve failed again make sure the charcoal canister isn’t coming apart. Charcoal will stick it open.
Those DMTL pumps suck right out of the box. The vehicle will run a test sometimes after the vehicle is shut off, but it usually just sounds like a pump running. The DMTL pump could cause some of the not accepting fuel but I think a stuck open purge valve could cork that vent closed. If that vent is not open when at rest the vapors can’t escape and will cause the pump to shut off repeatedly
 

MM3846

Well-known member
Feb 18, 2014
1,221
161
LI, NY
If this purge valve failed again make sure the charcoal canister isn’t coming apart. Charcoal will stick it open.
Those DMTL pumps suck right out of the box. The vehicle will run a test sometimes after the vehicle is shut off, but it usually just sounds like a pump running. The DMTL pump could cause some of the not accepting fuel but I think a stuck open purge valve could cork that vent closed. If that vent is not open when at rest the vapors can’t escape and will cause the pump to shut off repeatedly

I was thinking I could have killed it last summer trying to shove fuel into the truck, but I haven't had any issues fueling up at all since. I usually don't get the truck to a "full" tank but it seems like other people have that problem, too so not sure if it's related.

It was a "cycling" sort of sound. Buh. I'll order one of those, too. Changing the DMTL sucked. Charcoal canister looks like it's a a real bitch to change.
 

discostew

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Sep 14, 2010
7,706
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Northern Illinois
When you do the DMTL pump reach in over the right rear tire. If you Jack up that corner from the frame and let the suspension hang you can get on those 3 little torx screws. I use a little ratchet that accepts the bits.
 

p m

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Recall didn't touch the pump, but in our much-maligned LR4 the pump went about a year after the flange/filter failed.
I have not seen any codes, the truck just died on the side of the road. But I can imagine the pump being sub-prime for a long while, starving the high-pressure pumps and causing some bizarre behavior.
 

MM3846

Well-known member
Feb 18, 2014
1,221
161
LI, NY
Ok, had a good ole time getting the recall done. Dealer had the truck for a week, when I got it back it dumped fuel all over the place. They sent a flatbed and took it back, fixed it the next day. Apparently they didn’t tighten the filler neck tube.

I can smell fuel vapors around the back of the truck a little bit, still have the P0442 code so it looks like I have to smoke test it. Where do you guys run it? I called GAP and there is no provision in that tool for me to manually open and close the purge valve.

On the plus side, I’ve never been able to get 20 gallons in the tank to actually fill it, but I can now. So I got that going for me, which is nice.

CCE9D080-1FEE-40B8-A446-0D146E4C8D12.jpeg
 

MM3846

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Feb 18, 2014
1,221
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LI, NY
and another update:

found the pipe from the EVAP canister to the fuel tank disconnected (thanks dealership!) so I'm back to the intermittent "check gas cap" and P0442 code. I smoked the truck, but never found any leaks, and when I popped the fuel cap open after letting the smoke run for almost 10 minutes I never saw any. Looked underneath and I think I'm missing a hose?

1668788541169.png

A picture from google, since I couldn't get a good photo of it on my truck. There's nothing attached to that metal stub out at the body side. Anyone have an exploded diagram and part number? Everything I'm seeing shows it as an assembly. Maybe it fell off and is hanging on top of the subframe and I can't see it.
 

MM3846

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Feb 18, 2014
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LI, NY
Smoking out of the vent housing at the filler cap, but isn’t it supposed to leak there?
 
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MM3846

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Feb 18, 2014
1,221
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LI, NY
It should be drawing vacuum, not venting through the filler cap opening.
Right, under normal operation. I was pushing smoke through the pipe behind the purge valve going back towards the fuel tank. With the smoke coming out of the vent, it tells me there are no leaks anywhere. Or am I wrong? This sort of stuff is t my strong suit. I can hear the sucking when I open the gas cap filling with fuel, so that is pulling vacuum.
 
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p m

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Right, under normal operation. I was pushing smoke through the pipe behind the purge valve going back towards the fuel tank. With the smoke coming out of the vent, it tells me there are no leaks anywhere. Or am I wrong? This sort of stuff is t my strong suit. I can hear the sucking when I open the gas cap filling with fuel, so that is pulling vacuum.
My bad, didn't see that you were pushing smoke in. Need to do some reading on this evap system...
 
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MM3846

Well-known member
Feb 18, 2014
1,221
161
LI, NY
My bad, didn't see that you were pushing smoke in. Need to do some reading on this evap system...
Any chance you were able to check something out? Few more weeks left and til state inspection is up, the EVAP code is just persistent now. I have the service manual and it looks like to properly diagnose this with all the computery-doos, I need a T4 tool or similar to run the "Fuel Leak Check" forced test and the "Purge Valve Self Test."

1. Inspect / refit filler cap after smoke test (inspect filler neck for correct fitment to
pocket so that filer neck protrudes)
2. Run engine at idle; Using the manufacturer approved diagnostic system, run Purge
Valve Self Test (to clean the purge valve)
3. Check that the DMTL module wiring connector has been installed correctly and that
the seals around the connector body and individual wires are in good condition
4. Check all fuel system connections are correctly installed and secure
5. Visually inspect purge canister, purge pipes, fuel tank and filler neck for any
obvious damage
6. Try isolating the purge valve by fitting a blanking plug to the purge pipe
7. Carry out a smoke test
8. Replace the DMTL module

I found someone with a similar issue on a L322 that said his filler neck seal was not seated, what's that supposed to look like? (#1 on the list above). I replaced the DMTL with a Bosch unit and the purge valve with an OEM one 7/2021. It looks like the manual wants me to push smoke through the DMTL filter next to the fuel filler neck, or the purge valve (which I've done already) but I can give it a go through the filter this weekend.
 
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