sputtering hesitating when it is humid moisture

[Perry]

I am having an issue with my Astro van sputtering hesitating when it is humid moisture or raining. I get a PO300 DTC code (Random misfire)
It idles fine and only sputters when I step on the accelerator.
I brought it to a shop and they told me in a roundabout way they could start replacing things and see what happens or wait until it dies all the way. None of these are prudent choices in my opinion. So I was hoping that someone else has had this same problem and as a better idea what it might be. Thank you. Perry

[markmitch]

it may be a EGR valve , I once had a buick that did that till I replaced it.

[icebrrg3rd]

Usually when it is moist/humid/raining/damp and you have a misfire, it points right to the ignition system. Common culprits are either the distributor cap is cracked/bad or the plug wires are arcing. It's a common complaint here. If those are good then the coil would be next on the list.

-Andrew

[binder]

Three things I would check/change are coil, Distributor cap and rotor and possibly ignition Control Module. Spend the extra few bucks and get the AC Dleco parts, most of the time, they tend to last longer.

What will probably happen if you dont change them, is that it will become harder to start in time.

But 99% of the time moisture related problems are ignition related

[Jasen]

PO300 can be a PITA, don't ask how I know.
1st. place I'd look is cap&rotor for corrosion, crack's & clogged dist. vent screen's. ACDeleco really is the only way to go on these van's. Also check the rubber splash guard's in the front wheel wells aren't missing or folded up. Next unplug all your ignition & emission elec. plugs (1 @ a time), squirt them w/ WD40, blast them out with compressed air, remove rubber seal & clean them and plug body, apply dielectric grease to seal to insure a water tight seal and plug them back in.

[WoodButcher]

PO300 can be a PITA, don't ask how I know.
1st. place I'd look is cap&rotor for corrosion, crack's & clogged dist. vent screen's. ACDeleco really is the only way to go on these van's. Also check the rubber splash guard's in the front wheel wells aren't missing or folded up. Next unplug all your ignition & emission elec. plugs (1 @ a time), squirt them w/ WD40, blast them out with compressed air, remove rubber seal & clean them and plug body, apply dielectric grease to seal to insure a water tight seal and plug them back in.

x2, Start with the cap and rotor, AC Delco only. If you change the wires get a high quality 8mm set, plugs, stay away from splitfire and bullpuckies like that. AC Delco are good. It helps alloy to have help when you do the wires but the rest is easy. The doghouse is the biggest PITA in my book but I've gotten good at that, with luck you won't need to.

[Perry]

Thank you all for the great advice. I need to find a day to change the bearing hubs so I will have the rubber off and can look at the plugs too. Never had the dog house off but if it is anything like my c7500 probably will be one of those days where a lot of strange yelling comes from the inside of the van

[djwarren312616]

Big Yes on the ACDELCO parts all the way. I had sputtering at all speeds and particularly noticable above 70mph. Changed plugs, wires, cap & rotor and she runs smooth as silk now. For the doghouse and the plugs I would buy yourself a long extension (12in+) spark plug socket and then if your really up to it, buy a bit for a drill (mines 18v Dewalt) to mate to the extension, makes the doghouse much easier. Also easier to get most the plugs from the side behind the tires with the extension.

[Jasen]

https://www.astrosafari.com/viewtopic.php?f=43&t=13085

[binder]

Taking off the doghouse is not really that bad, sure it adds another 30-40 mins to almost any job, but if you are replacing ignition components in the winter, at least you have some protection from the elements. Spark plugs take way too long to change on this van, especially the last two on the drivers side.

I often wonder, is this vehicle is a marvel of engineering, how they got everything to fit into the small spaces provided, using up common components. Or if it is an engineering nightmare, thought up by some drunken GM engineers, trying to use up as much **** old inventory as possible, with out giving a single thought to anyone having to perform repairs or logical placement of components?

I usually tend to think it is the latter.

[Perry]

Yes I agree, it is most likely the later I replaced the window regulators and the power door lock actuators last year. Turns out they are the same parts from the Firebird/Camaro line

[Jasen]

Taking off the doghouse is not really that bad, sure it adds another 30-40 mins to almost any job, but if you are replacing ignition components in the winter, at least you have some protection from the elements. Spark plugs take way too long to change on this van, especially the last two on the drivers side.

I often wonder, is this vehicle is a marvel of engineering, how they got everything to fit into the small spaces provided, using up common components. Or if it is an engineering nightmare, thought up by some drunken GM engineers, trying to use up as much **** old inventory as possible, with out giving a single thought to anyone having to perform repairs or logical placement of components?

I usually tend to think it is the latter.

Look at the newer F250's and up, you have to pull the cab to anything more then check the coolant level.