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Wed Apr 09, 2025 12:00 am

Been having some pretty consistent start up issues but there is a very obvious pattern.

When I attempt to start the van it cranks and starts but has very, very low idle around 100-200 rpm then dies within 3 seconds or it will just fail to start altogether. The pattern here is that it always fires right up effortlessly on the second attempt and runs perfectly fine. So it almost feels like something is maybe clogged and is being cleared up after the initial cranking, which is why is always starts up on the second attempt.

I'm hoping someone here can help me out, thanks!

These things have been replaced recently:

- Spark plugs
- Fuel pump
- Fuel filter
- Ignition switch
- Starter
- Fuel tank reseal
- Battery

Details of the van:
1987 Vanagon 2WD
Manual transmission
2.5 Subaru engine (from a 2003 Impreza)

Wed Apr 09, 2025 5:06 am

Seeing as you have a "modern" conversion I would suggest inspecting the Idle Control Valve. If that is not used in Subaru conversions maybe someone will correct me, but on Zetec conversions our Idle Control Valves can become gummed up and not respond appropriately. Initial start up will have low/erratic idle until things warm up.

If this is the case you can remove and clean it with solvent or replace the whole unit.

Once again, this is only in the assumption that Subaru conversions keep the Idle Control Valve during the swap.

Wed Apr 09, 2025 10:28 pm

Subaru engines do use an idle control valve, and someone else actually thought it might be that as well so good to know a second person is saying the same thing.

I will check out the idle control valve later this week on Friday to see if it's the culprit. If it in fact is the idle control valve, does anyone have any opinion on if it's fine to just clean or better to just buy a new one? This is probably the original one so it's at least 20 years old.

If anyone has any thoughts on what else could be causing these failed starts though, would appreciate some more input. Thanks!

Thu Apr 10, 2025 12:09 am

Codes? Could be low fuel pressure due to faulty fuel pressure regulator. Cycle key to ON a few times to cycle the fuel pump then try to start it. Could check fuel pressure as a double check before buying part.

Fri Apr 11, 2025 2:36 pm

So I cycled the key to on a few times this morning and it started right up the first time, instead of normally the second time.

Does doing this help build up more than normal fuel pressure, which in turn helps start the engine by clearing any gumming (temporarily) in the idle control valve or the fuel pressure regulator?

Fri Apr 11, 2025 2:54 pm

One possibility is that the fuel pressure regulator slowly leaks down as the engine sits. Repeated cycling of the key builds up pressure which holds long enough to easily start.

You can test the operation of the regulator by installing a simple hose and pressure gauge on the fuel line tee on top of the block. There is a small screw you remove to open the test port. Just push a hose (¼"?) over that port.

Fri Apr 11, 2025 5:20 pm

With the green test connectors together and key to ON, the fuel pressure with a good regulator cycles 40-45 psi consistently on my 02 2.5L with VW pump. If the 40 psi starts falling between cycles it's a bad sign even before hard starting symptoms appear. Got one from Rockauto. Replacing it is DIY.

Wed Apr 16, 2025 10:29 pm

So since the van started on the first try after cycling the key on and off a few times, does this mean that it's more likely the fuel pressure regulator or the idle control valve?

Wed Apr 16, 2025 11:13 pm

Cycling the key on to position 2 (not cranking) causes the fuel pump to prime the fuel lines. You do that a couple times, it's primed, and it should start easier.

If that's the case, check the fuel regulator like others suggested.

Cycling the key doesn't do anything to the idle air control valve (IACV), I'm fairly certain. Still doesn't mean it's not dirty though.

Thu May 15, 2025 6:30 pm

Just wanted to post a update on this, turns out it was the idle control valve. I removed it and it was really dirty! I cleaned it up with some MAF cleaner I had lying around, plugged it back in and it's been turning on like butter every time now. Thanks everyone for the advice on input on this.

Thu May 15, 2025 11:21 pm

Cycling the key had it start first try but it turned out to be a very dirty IACV? Weird! Did you not have issues with it stalling at stops before this?

Fri May 16, 2025 4:56 pm

Yeah sometimes it would stall at stops, but that is only if it started but with low RPM and I decided to just drive and I would gas it a bit so it wouldn't stall. But typically if it started but had really low idle, I would turn it off then back on because I knew something wasn't right, then I would prime it with the cycling key method and then it would start with normal RPM.

Fri May 16, 2025 6:05 pm

No code? My 02 2.5 threw a code for the IACV when it started stalling and it was good after cleaning.