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Tue Jan 16, 2024 8:18 pm

Tried posting in the performance forum but thought there may be more input hear. Have an ej25 from a 99 forester. It will start and idle just fine but as soon as i press the throttle it will jump to 2000+ rpm and just stay there. If I press throttle again it will jump ever higher. It won't settle back on its own I have to shut it off. When restarted its back to the stable idle, around 800rpm. There are no codes, tps is zero when off throttle, throttle plate is closed and no vacuum leaks i can find. Anyone ever experience this?

Wed Jan 17, 2024 4:25 am

Leadsled1962 wrote: , throttle plate is closed

How do you know?

Wed Jan 17, 2024 4:53 am

I removed intake boot prior to starting and confirmed throttle plate was closed and took note of cam and hard stop on throttle body arm. Checked that position again after starting.

Wed Jan 17, 2024 7:38 am

At first it sounded like a sticking throttle cable, but that wouldn't explain why it starts low on the restart.

It's almost like some sensor, possibly the throttle position sensor, gets confused when the throttle is pressed.... Even possibly ECU?

Sounds more like a generic subaru issue than anything to do with a specific conversion.

Have you checked the Subaru vanagan group?

It also be a good question for some of the Subaru groups like NASIOC.

Wed Jan 17, 2024 5:21 pm

What VSS are you running?

Wed Jan 17, 2024 5:56 pm

The few issues I've had getting my 03 up and running since August, first was a vacuum leak at the large lower injector seals for the air injector, had to sand the corroded aluminum around the manifold sealing surface, that was from assembling them, shouldn't leak there if undisturbed. Second the TPS was out of adjustment, on decel the engine would idle high even when warmed up instead of cut fuel to slow down. I set it with a multi meter probing the back of the ECU, I think it's 0.5v at idle. It will also idle high if it senses it's about to stall for example when not slipping the clutch enough, it will idle at 2k for about 10 seconds then run normal.
I would suspect an iac issue if the throttle is closed. Try to unplug it and see how it acts then if your able to block off the vacuum inlet to the iac see if that changes the issue.

Wed Jan 17, 2024 6:31 pm

VSS is from Busaru. It simulates a signal rather that mounting at the wheel. I'll double check tps and iacv readings.

Wed Jan 17, 2024 6:43 pm

Leadsled1962 wrote: VSS is from Busaru. It simulates a signal rather that mounting at the wheel.

disconnect it and report back

Wed Jan 17, 2024 6:51 pm

skills@eurocarsplus wrote: Leadsled1962 wrote: VSS is from Busaru. It simulates a signal rather that mounting at the wheel.

disconnect it and report back

^^^100%. Was experiencing exact same issues with a simulated VSS board. Fixed after disconnecting on advice from skills. Swapped to a cv mounted vss.

Thu Jan 18, 2024 5:55 pm

You guys are great, that was it. problem resolved immediately after clipping the vss. I get to work on installing a physical sensor.

Thu Jan 18, 2024 6:46 pm

He also sells a physical sensor. It’s a pretty generic sensor but very convenient to have a little bracket that is ready to bolt up.

Supposedly you can feed it 12v but my ‘94 Subaru ecu diagram says it should be receiving 5v signal so I use a 12-5v converter.

Thu Jan 18, 2024 6:49 pm

https://www.hawkusa.com/manufacturers/zf-formerly-cherry/switches/hall-effect/gs100502

Another option. Would need a bracket off transmission.

Thu Jan 18, 2024 9:00 pm

those simulated VSS deals are a joke. just wire up a real VSS and enjoy how smooth these run.

Fri Jan 19, 2024 8:31 pm

danielheff wrote: He also sells a physical sensor. It’s a pretty generic sensor but very convenient to have a little bracket that is ready to bolt up.

Supposedly you can feed it 12v but my ‘94 Subaru ecu diagram says it should be receiving 5v signal so I use a 12-5v converter.

I think 5 pulses per revolution is more important as that is what Subaru uses. My first VSS was a reed switch in the OXS mileage counter in the two part speedo cable. It was just a switch for ECU VSS pin to ground. 4 pulses per rev it worked OK but not accurate. Same 6 pulses per rev using CV bolts is not accurate. Some sensors will work directly with 5v.(eg. Smallcar's Littlefuse sensor) even though they say to connect it to 12v ignition. Check your sensor specs.