legacycentral bbs

Normally I'd suspect IAC but 3000rpm is some pretty good throttle input. Can't be lack of fuel or weak since it runs great wide open when those systems are under the most stress.

It only does this when you lift off the throttle while driving. It hot and cold idles just fine. It only dies when you take your foot off the gas while driving.

I'm thinking maybe MAF.

Thoughts?

What about the tps. Does it take off again if you give it gas?

jefferson wrote: ↑Sun Oct 24, 2021 3:18 am What about the tps. Does it take off again if you give it gas?

If you gas it when it's trying to stall it will stay running but you gotta stay on the gas enough to keep it running. If you take your foot off it will try and stall.

This isn't happening 100% of the time. The behavior is intermittent. Like I said it idles fine.

I'll probably swap a TPS off a different car rather than buying one and see if that fixes anything.

Last night I swapped the MAF for one that was working fine when pulled from a car 2yr ago. We'll see how it does today. The old one had 3x as much black stuff (i.e. brake and tire dust that passed the filter over the last 200k) as the "new" one. We'll see how it does...

Let us know how it goes. I had similar stalling issues while driving and it was the MAF.

Died again and wouldn't restart today so that wasn't it.

I'm not sure what else it could be. TPS isn't in the "critical path" so that shouldn't cause a no-start condition.

Maybe crank sensor?

The problem only shows up when the car is warm so I don't suspect fuel delivery or ignition issues since those should show up regardless of temperature. The fact that it has slight trouble restarting tells me it's not the oxygen sensor.

Is there any sensor I can unplug that will cause the car to run in open loop all the time? It would be nice to see if I can isolate the problem.

How old is the coolant temp sensor?

If you unplug the coolant temp sensor and try to drive does the problem still exist?

Same question if you unplug the O2 sensor and try to drive?

Legacy777 wrote: ↑Tue Nov 02, 2021 6:25 pm How old is the coolant temp sensor?

If you unplug the coolant temp sensor and try to drive does the problem still exist?

Same question if you unplug the O2 sensor and try to drive?

I'll try that after work or this weekend, whenever I get around to looking at the car next.

Coolant temp sensor is 6-10mo old. The prior one was keeping the fans on all the time. Maybe the replacement is a lemon.

I just don't see the coolant sensor making the fuel trims rich enough to stall the car though. If it were out of range in the high direction the fans would be on.

I'd also vote for CTS issue.

FWIW, my '98 Forester - very similar setup to yours (a different TPS and ECU - ok kinda different) - had similar issues. Idled fine, ran fine above 3K, but mine would stutter and hesitate to accelerate from 1500-3K. I fount two possible causes:
1 - wrong bolt on bottom right of IAC - was too long and probably caused a vac leak
2 - stuck injector. Took all 4 to a local injector shop and was told one was 'sticky'.

Fixed both and the stutter/hesitation is gone.

GL,
Td

The coolant temp sensor can cause all sorts of weirdness from my experience so I wouldn't rule it out without doing some testing.

Did you use a new Subaru temp sensor or aftermarket? The Subaru one should be around $20 and it's what I'd recommend using.

The car sat for a week and won't start regardless of whether temp or O2 are plugged in

What's fuel pressure supposed to be on these? I removed the fuel line coming from the filter and fuel just kinda dribbled out while it was cranking which doesn't seem right for an EFI system.

I sprayed it with starting fluid and it ran great (massive exhaust leaks notwithstanding) so that seems to point to fuel.

Possible my "new" $20ish fuel pump is dead after only ~10 operating hours? It was aftermarket but it's 2021 and I don't think it's unreasonable to expect an electric motor with molded plastic on the ends to cost more than that.

I used a cheap aftermarket temp sensor FWIW

Fuel pressure should be around 36 psig if I recall correctly.

There is connector under the rear passenger seat area that is notorious for shorting out and causing issues. I'd recommend checking that and that the pump is getting the proper voltage. What I did is pull the pins, cut the wire, and used the appropriate wire size insulated spaded connectors.

Legacy777 wrote: ↑Mon Nov 29, 2021 6:46 pm Fuel pressure should be around 36 psig if I recall correctly.

There is connector under the rear passenger seat area that is notorious for shorting out and causing issues. I'd recommend checking that and that the pump is getting the proper voltage. What I did is pull the pins, cut the wire, and used the appropriate wire size insulated spaded connectors.

Will it be obvious upon inspection if the connector is failed? Like will there be corrosion or something? Or do I have to test it for voltage drop?

It may or may not be obvious. On my car the connector was a little brown which could possibly indicate it had gotten warm. You can check for voltage drop and continuity as well (make sure the ignition is not on when you test for continuity across the connector).

Here's a pic of the connector and what I did. The two smaller yellow connectors are the new connectors I added.

New fuel pump fixed it.

I couldn't find the connector but I was looking on the driver's side. If it causes problems again I'll a) check out the connector.

Ok, good to hear you got it fixed.

Fuel pump on one of the other cars died 10ft after filling up with gas. The OEM fuel pump lasted 210-230k on the white car and this one has 245k on it so I'm not exactly surprised.

Thankfully I bought multiple to have in stock after the ordeal with the white car so it was just a case of getting my girlfriend to find it and bring it to me.