Engine idle drops and dies after cold cranking?

The description sounds like separated fuel. Ethanol loves to pull moisture out of the air and then that settles into the tank. With the nose tilted down that may be enough to settle the bad mix under the fuel pickup in the tank and you get this response from the engine getting a larger amount of a water/ethanol blend than it can handle. The cold means that the PCM tries to run a richer mixture and that dumps more of the crud into the engine and you get misfires and the engine stalls. I would suggest running it down farther then filling it with non-ethanol fuel. Running more fuel out of it should help remove the moisture.

I thought it might be fuel related. I don't remember how much fuel was in the tank the first time, but the second occurrence I just filled the tank the day before

It can be easily with modern fuels. Especially if you got a bad batch like some folks in Colorado got, theirs was diesel in the gas but water can be much worse.

Ok that's good it could just be fuel. I'll run some of the "good stuff" in it and see if that helps

Let us know. FYI it does have a fuel filter but it is in the fuel tank as part of the pump assembly. As such you normally just change out the complete assembly instead of just the filter, but it sounds more like the fuel itself.

I think I've narrowed it down it only seems to do it when parked facing downward on a hill AND I turn the heat on. It did it to me twice this morning and I had to crank it back up again. The third time I didn't turn the heat on and it stayed running. Once I was driving down the road I turned the heat on and it ran fine no issue, even on hills. Very strange...

Strange. If turning on the heat means you turned the blower motor up in speed that would increase the load on the engine. Try this, park nose down and turn on the headlights, does it stall then? The description you gave earlier still sounds fuel related though, like it's running out of fuel and stalls. I would put a fuel pressure gauge on it and see what the fuel pressure does when it stalls, as well as what the pressure does under normal conditions. For that you T the pressure gauge in the line that feeds the fuel rail under the hood. Normal fuel pressure with the engine running should be between 55 and 65 PSI. So if you see 40 psi and it drops off when you do the test we need to determine if it's the fuel pump or if it's electrical from the increased load that is causing the pump to slow down.

Ok now today I was parked in a flat parking lot with the heat on and anytime the compressor kicked on the engine would shudder and RPMs would drop way down, then it would ramp back up on its own. I turned the heat off and it idled fine the rest of the time I waiting.

I would run a fuel pressure check on it, low pressure could cause it to run under lower power and cause it to stumble, No CEL on correct? May also need a throttle body cleaning if it doesn't jump up the idle fast enough.

Yes no CEL at all. My neighbor has a fuel pressure gauge I'll see if I can check it. Might be a bit since this ice storm is coming tonight. I'm leaning towards fuel pump myself, as sometimes it turns over for a few seconds before firing up, making me think the fuel pump is getting weak.

Yeah, that is a sign of a failing pump. Waiting for the storm myself, already got the low temps.

What's the best way to replace the fuel pump assembly? Just pull up the carpet in the back and take it out through the floor? Also, you said the filter was part of the assembly so there's not one in-line? I was going to just buy the whole thing but wanted to make sure

No inline filter, just the one on the pump assembly in the tank. Not a hard one to access. Move the second row seat forward fully, then lift the carpet and you will find an access panel. Remove it and under it will be the pump, clean off any crud before you proceed. Now disconnect the harness and the quick connect for the fuel line. Then you unscrew the retaining ring and once it's off, the pump lifts out, watch out for the level sender. Now you should get new seals in the kit. The wide one goes in the tank, the pump goes through it and the ring goes on top under the retainer. I like to give them a very light wipe of silicone grease, just so things go together better. If you have spray silicone it works as well. Set the pump in and align it as shown. Align the arrow on the retaining ring with the first thread on the tank and tighten down the ring. The ring gets torqued to 52 ft lb if using a drive tool on it. Now inspect the harness, they can loosen up or corrode and it's much easier to replace the pigtail now then after you put things back together and discover there is a problem. Then attach the fuel line and plug it in and test it, try to rock the vehicle to be sure the level sender works. For the plate, if the original goop is still soft you can re-use it, If it's not a bead of caulk will work, it's just to keep fumes and critters out.

Alright I ordered the fuel pump assembly here's hoping this fixes the issue. It's also time for new brakes so it's gonna be a long day of car work lol

Let us know what you end up with. Good luck.

Ok the new fuel pump assembly is installed and it's running good so far. I'll report back if any issues tomorrow when I know I'll be parked on a hill with the heat on again. If not, it's fixed!

Hope to hear good news.

So far so good. Past two mornings I've had it parked nose down on a hill with heat on and the RPMs never dipped once. Thanks

Sounds like you got it taken care of. Good job.

Whelp, it ran fine for a while and now it's back to dropping idle and shuddering the whole van again. It only does it when idling in park, whether the heat is on or not. If I'm sitting at a red light or driving down the road, it's fine so the issue is with it idling in park

Only at idle, what does it do if you slightly increase the engine speed while setting? How about this test, Put it in drive and hold the brakes, now turn the blower to high, the headlights to high, wipers on. How does it act now? Trying to see if maybe it's electrical, did you do a fuel pressure test on it?

I did an battery load test using a tester with everything cranked to MAX and the voltage was within spec and steady. I haven't checked the fuel pressure I have to see if my neighbor can find his gauges.

Also, I've noticed a chattering sound when accelerating, could a valve adjustment fix all of these issues? It's been over 100K miles since it was done last time

It wouldn't hurt if it's been that long, however they normally wear and gain clearance and clatter. You said it ran better for a while but now acts up, did you disconnect the battery when you did the other work? I'm wondering if maybe there is a different issue. If you did, unhook it again, let it set a few minutes and reconnect and see if it still acts up? It might still be fuel related but on the other end, the idle is controlled by the throttle body and there is a relearn procedure that it follows and then adjusts over time, however if the throttle body is dirty inside it can cause a low idle as the throttle doesn't compensate properly.
Take a look in the throttle body and see if it has any built up crud, soot. If it does clean it and see if it helps. Book says you need to pull the TB to clean it, but if you have access I generally don't, instead I use a dowel rod wrapped with a towel and spray that with cleaner and scrub out the bore.

https://www.2carpros.com/articles/throttle-actuator-service

I actually tried to clean the throttle body when I changed the oil last, but couldn't get the air cleaner hose off due to some hard-line hoses connected to it that I couldnt get off. I guess I'll end up taking it all apart anyways to adjust the valves since it's clattering.

Sounds like a plan.

Ok after reading about how to do the valve adjustment, I ended up making an appointment at the Honda dealer to get it done.

Today I was sitting there idling in a parking lot and out of the blue the CEL came on (finally) but I didn't notice any shuddering or idle drop. Checked the codes and it was "system too lean" on bank 1 and 2. I forgot to mention when I tried to take the air cleaner hose off to clean the throttle body, the hose had a few splits in it, so I guess it's sucking too much air? I got a new hose I'm going to take with me and let the dealer put it on when they adjust the valves and clean the throttle body, hopefully that fixes the issue.

Yep, split hoses can do that as they will cause it to run lean and may cause the other issue you have as well. At idle is when the engine creates the highest vacuum and cracked hoses would cause it to act like it has low fuel pressure and run out of gas. Might want to stick the new hose on and see how it acts. May also want to get a can of carb cleaner and spray some around the other hoses. See if any others are pulling in air. Then if it runs good with no issues you can save some money, unless they are not charging you a ton for the valves.

Ok valve adjustment, throttle body clean, and new intake hose all done today. Here's hoping that fixes everything!

Please let us know, STEVE W. is one of our best!