Bucking Under Heavy Gas & Higher RPMs

[driverdave]

I have an 84 Westy with a 91 Subaru 2.2 that's been running well up until the last 100 or so local miles.

A couple of times leading up to today, it felt like someone turned the key off, pressing on the gas had no effect, but this would end rather quickly, within 10 seconds or so. Happened maybe 3 or 4 times.

Today, the van would start but the engine would surge between 500 and 1500 RPMs, and then stall if I hit the gas. I was able to limp it around a little bit, but every time I would get above 2500 RPMs or so, it felt like someone was squeezing my fuel line. Pressing on the gas pedal would result in worse performance, and the engine seemed starved of fuel. Lots of bucking if I tried to gas it harder.

Van was low on fuel today, I thought I ran out, but same symptoms now that it has about a 1/2 tank of gas.

Installed a new fuel filter within a year or so. Fuel tank is maybe 3 years old.

I'm leaning towards a bad fuel pump. I can hear it when I turn the ignition, but it seems like the engine is not getting the fuel it needs. Can fuel pumps fail like that, where they work but don't pump the required fuel pressure?
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1984 Vanagon Westy with a 91 EJ22 KEP Conversion

[tjet]

My fuel pump went like that.

[danfromsyr]

bucking is a good indication of a lean operating symptom.
mine did that also when the fuel pump died.
have a 1989 ford f250 pump now the last few years.
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[driverdave]

Hi Dan! Those clutch parts are still running strong, van has been cross country with no further clutch issues, thanks again!

This issue ended up being a bad Subaru mass airflow sensor. When I started the van without it plugged in, it ran way better. Although I've read that this is not a definitive test (I think the ECU disables some other inputs if it sees the MAF missing) it was a bad MAF in my case.

Grabbed a used one from a pick n pull and the van is running strong again.

This has got me motivated to get some gauges installed so I have a better idea of what is going on when things act up.
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1984 Vanagon Westy with a 91 EJ22 KEP Conversion

[danfromsyr]

Ohh, Hey great..
it's tough to nab parts in a pinch. and Vince is a great guy/friend/mechanic..

you may be able to read the OBD-I system for some of the ECU inputs & vitals. check with the Subie guys.
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[driverdave]

Yeah, deciding on whether to piece together a real time OBD1 diagnostic tool for the EJ22.

This guy has a great writeup http://www.4bc.org/vanagon/engine.html

Tempted to put together that Evoscan tool.
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1984 Vanagon Westy with a 91 EJ22 KEP Conversion

[WestyBob]

Driverdave -- good job diagnosing that. I have a subie power plant but haven't run into that problem yet.

[driverdave]

[driverdave]

Got the Evoscan cable & software.

Works well! Probably could have made the cable for far less, but I appreciate the effort, and the software is nice, so happy to support them. If you have an EJ22, would recommend this, nice to be able to see live engine diagnostics.

This has me motivated to start an Arduino project for a dashboard gauge. Going to try to cobble together something to pull the water temp reading from the Subaru SSM port. After that, will try to add in an oil pressure gauge.

Just ordered a basic Arduino starter kit to get familiar with things.
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1984 Vanagon Westy with a 91 EJ22 KEP Conversion