7 replies to this topic

[El_Freddo]

1999/2000 Subaru Liberty.

I’m wondering if anyone knows of a way to fix the harsh/sudden off throttle to idle and from idle to on throttle response of the EJ251?

I’m specifically looking at low load and coasting situations - cruising in 4th or 5th around town at 60km/h, slow manoeuvring in car parks in 1st gear.

I’ve put up with it for some time and now I’m thinking if there’s a way to sort it. An old mate of mine sold his outback over this throttle response issue! Apparently he tried many things, one of them I remember was a progressive throttle cable wheel so lots of foot movement was needed from zero to small throttle openings. That didn’t work. I think the issue is the plunger style IACV.

Knowing this, I’m wondering if anyone knows:
A/ Does the EJ202 suffers the same throttle response issues?
B/ Could the factory ECU accept a different throttle body from a later model that uses a better IACV rather than the plunger style of the EJ251?

Lots of wondering on this one. I want to avoid buying parts only to find they don’t work because the ECU doesn’t accept them. But this might be the only way.

Also, anyone know what sort of IACV the EJ202 uses?

[allpaw4]

Its something that seems to be the same with most gen3's in my experience, not just the 251's. My H6 did it, although much less noticeable with the auto. And the 201 that was in the GX also did it. But. All of my cars have all had reasonably high to very high kms. H6 had around the 360 to 370 mark, 201 had 390, and the old 251 I had that was doing it was 230ish. I've got no idea what causes it, but I'll be very interested in what you find out. It would stand to reason that the IACV or TPS would be the culprit though.

If I find some time in the next few weeks, I can have a look at the old 201 engine thats sitting out the back of the shed.

Cheers,
Ben

Edit, the reason I thought about this recently just came into my head... Last week this happened to me in the gen5. Very light throttle input results in a disproportionate increase in revs, particularly once the car is at temp.
Hence why this post peaked my interest Bennie!

[El_Freddo]

I believe this issue started a very long time ago - and I know I’m not the only one! I’m just at the point that I’d like to do something about it. This issue is the worst part about this vehicle experience I reckon.

The plan with Basil is to keep him going so my sister’s mate’s daughter can learn how to drive manual with him. This got me thinking about this on/off throttle response issue. Putting your foot on the clutch pedal with a tiny bit of pressure can reduce the symptoms by allowing some clutch slip when in a carpark situation, but this isn’t the way to learn to drive nor is it the solution and it doesn’t help with light load and town speed limit cruising.

Interesting that your Gen5 is doing it to some degree.

I’ll have to pull the IACV plunger and check it out. It’s been a number of years since I’ve looked at it. Maybe it just needs a new rubber seal? Maybe - long shot here - a bbq gas bottle/hose grommet could possibly do the trick. Worth a try for a few bucks. I’ll look into it.

Got a pick a part run planned, I’ll look at other throttle bodies and see if anything might be worth further investigation if they’re not too expensive.

Lots to ponder.

[duncanm]

Make sure its not excessive drivetrain lash, shagged diff bushes,  engine mounts, pitch stop mount, etc etc.

 

All of those things exacerbate the feeling of a harsh on/off throttle.

[Barbbachello]

If we're talking about the jerking around when say cruising in a carpark in 1st gear around 20kmh. My understanding is its the ecu turning the injectors off/pulsing for emissions/economy things

Goes away/is miles better with an aftermarket ecu. Tune may also fix it

Not a viable solution for an NA shitter

Doubt swapping the IACV would work. The gen 3s are usually 6 wire stepper motor setup. Everything else is 3 wire PWM type operation

[El_Freddo]

Thanks Duncan, I’ll look into the bushes, I think they’re ok as this issue was there from day 1.

I reckon you’re on to it barbs, it feels like a sudden switch off of something. Typical Subaru to make this model’s IACV different to everything else in their line up!

Interesting that they cut the injectors for emissions but let it “run on” when it’s cold and you just want the revs to return to idle or some sort of a downward trajectory before tomorrow when it does it. Makes downshifting worthless.

Thanks for the input fellas. Good for thought.

Allpaw, might want to check your mounts as per Duncan’s suggestion.

[El_Freddo]

After thought this morning on my way to work: I’m guessing the factory ECU can’t be “tuned” to get this issue sorted..?

[allpaw4]

Yeah, mounts are fine in the gen5, its not a small step in revs, like 1 to 200, probably the CVT switching something on once it detects the throttle pedal isn't at 0%. Might be a "dead spot" on the pedal in the ecu settings too, so it immediately jumps to a 3-4% on or something. Scaling issue on the pedal input? So many things it could be when everything is electronic, but it's not something thats really concerning me that much, more so curiosity when you started this thread!

Cheers,
Ben