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Leadsled1962 Samba Member
Joined: March 13, 2017 Posts: 12 Location: KENTUCKY
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Posted: Tue Jan 16, 2024 8:18 pm Post subject: EJ25 High Idle Issue |
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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? |
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vanis13 Samba Member

Joined: August 15, 2010 Posts: 4382 Location: ABQ NM USA.... Except when not
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Posted: Wed Jan 17, 2024 4:25 am Post subject: Re: EJ25 High Idle Issue |
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Leadsled1962 wrote: |
, throttle plate is closed |
How do you know? _________________ 83.5 Westy with Subaru 2.5, 4 spd manual, center seat, COLD A/C on 134a!, Winter camp heated with an Espar B4 gasoline furnace
www.SuperVanagon.com - some stuff I make |
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Leadsled1962 Samba Member
Joined: March 13, 2017 Posts: 12 Location: KENTUCKY
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Posted: Wed Jan 17, 2024 4:53 am Post subject: Re: EJ25 High Idle Issue |
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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. |
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vanis13 Samba Member

Joined: August 15, 2010 Posts: 4382 Location: ABQ NM USA.... Except when not
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Posted: Wed Jan 17, 2024 7:38 am Post subject: Re: EJ25 High Idle Issue |
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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. _________________ 83.5 Westy with Subaru 2.5, 4 spd manual, center seat, COLD A/C on 134a!, Winter camp heated with an Espar B4 gasoline furnace
www.SuperVanagon.com - some stuff I make |
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WillRB Samba Member
Joined: October 23, 2020 Posts: 227 Location: Ohio
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Posted: Wed Jan 17, 2024 5:21 pm Post subject: Re: EJ25 High Idle Issue |
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What VSS are you running? _________________ 1984 Vanagon Westfalia w/ Subaru Conversion (99 Legacy 2.2 Phase II) 2WD 4speed 4.57 R/P (.828 straight cut 4th) GT TBD |
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dvom Samba Member
Joined: April 27, 2020 Posts: 16 Location: West Haven, CT
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Posted: Wed Jan 17, 2024 5:56 pm Post subject: Re: EJ25 High Idle Issue |
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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. |
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Leadsled1962 Samba Member
Joined: March 13, 2017 Posts: 12 Location: KENTUCKY
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Posted: Wed Jan 17, 2024 6:31 pm Post subject: Re: EJ25 High Idle Issue |
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VSS is from Busaru. It simulates a signal rather that mounting at the wheel. I'll double check tps and iacv readings. |
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skills@eurocarsplus Samba Peckerhead

Joined: January 01, 2007 Posts: 17829 Location: sticksville, ct.
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Posted: Wed Jan 17, 2024 6:43 pm Post subject: Re: EJ25 High Idle Issue |
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Leadsled1962 wrote: |
VSS is from Busaru. It simulates a signal rather that mounting at the wheel. |
disconnect it and report back _________________
gprudenciop wrote: |
my reason for switching to subaru is my german car was turning chinese so i said fuck it and went japanese....... |
Jake Raby wrote: |
Thanks for the correction. I used to be a nice guy, then I ruined it by exposing myself to the public. |
Brian wrote: |
Also the fact that people are agreeing with Skills, it's a turn of events for samba history |
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WillRB Samba Member
Joined: October 23, 2020 Posts: 227 Location: Ohio
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Posted: Wed Jan 17, 2024 6:51 pm Post subject: Re: EJ25 High Idle Issue |
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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. _________________ 1984 Vanagon Westfalia w/ Subaru Conversion (99 Legacy 2.2 Phase II) 2WD 4speed 4.57 R/P (.828 straight cut 4th) GT TBD |
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Leadsled1962 Samba Member
Joined: March 13, 2017 Posts: 12 Location: KENTUCKY
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Posted: Thu Jan 18, 2024 5:55 pm Post subject: Re: EJ25 High Idle Issue |
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You guys are great, that was it. problem resolved immediately after clipping the vss. I get to work on installing a physical sensor. |
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danielheff Samba Member

Joined: January 22, 2016 Posts: 168 Location: San Diego, CA
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Posted: Thu Jan 18, 2024 6:46 pm Post subject: Re: EJ25 High Idle Issue |
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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. _________________ '70 Squareback 1835cc
'85 Vanagon GL Camper, EJ22, Peloquin Diff, Burley rear disc brakes, SC big front brakes, Espar D2L, 250ah Lifepo4
'85.5 944 NA |
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WillRB Samba Member
Joined: October 23, 2020 Posts: 227 Location: Ohio
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skills@eurocarsplus Samba Peckerhead

Joined: January 01, 2007 Posts: 17829 Location: sticksville, ct.
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Posted: Thu Jan 18, 2024 9:00 pm Post subject: Re: EJ25 High Idle Issue |
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those simulated VSS deals are a joke. just wire up a real VSS and enjoy how smooth these run. _________________
gprudenciop wrote: |
my reason for switching to subaru is my german car was turning chinese so i said fuck it and went japanese....... |
Jake Raby wrote: |
Thanks for the correction. I used to be a nice guy, then I ruined it by exposing myself to the public. |
Brian wrote: |
Also the fact that people are agreeing with Skills, it's a turn of events for samba history |
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wesitarz Samba Member
Joined: August 20, 2012 Posts: 1730 Location: Victoria,B.C.Canada
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Posted: Fri Jan 19, 2024 8:31 pm Post subject: Re: EJ25 High Idle Issue |
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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. |
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