Subaru Legacy 2.5 long cranking when cold / hesitation when smashing gas pedal

[legacy200425]

Hello guys,

 

could someone help me with following issues ? When i try to start the car early in the morning in cold weather it takes like 10-15 sec, once its warmed it starts without problem. There's also a big flat spot when i try to smash gas pedal or when i try to accelerate from a stop. I've replaced maf sensor, cleaned map, new fuel pump, new spark plugs, previous owner replaced coil pack.

 

Please does anyone have any idea what to look for ? Because atm i'm kinda desperate.

 

adding link to video + live data

 

[JoeInOregon]

Will start by saying I'm far from the right person to ask but sounds fuel related, clogged filter, dirty injectors.

 

Also more info when it started if you had this issues sense you got it, stock or tune , any fuel system modification extera, and some logs of some kind.

 

Fuel filter and some Lucas oil injector cleaner is a good place to start if you have no codes.

 

Sent from my Pixel 3a using Tapatalk

[darthqwo]

possibly throttle body issues--possibly carbon build up on plate--or drive by wire or compression

 

what software is that and how are you connected

[legacy200425]

possibly throttle body issues--possibly carbon build up on plate--or drive by wire or compression

 

what software is that and how are you connected

 

Hi, it's drive by wire. Throttle body has been cleaned, gasket is quite old so im waiting for new but i dont think there will be difference. I'm using Free SSM

 

I also tried different crank sensor and no difference.. The problem is that if u build up rpms slowly its good.. but if u tap gas pedal fast there's a 1-2sec where it "chokes" then rpms go up.. I also guess

long cold starts has something to do with this. I tried switching the key few times to build up pressure for the start but no difference. Once its warmed up starts all fine.

Edited November 17, 2021 by legacy200425

[MoleMan]

Now here’s the question. What kind of plugs did you use? The fourth Gens hate Iridium plugs so that could be the culprit. Every time I change out my plugs someone always to be in the store complaining about their fourth gen GT or other model running like crap after they sold them iridium plugs.

 

Or the other culprit is the injectors. But those generally will throw a code of something is an issue.

 

By chance where do you live? Could be running like crap because of the winter blend fuel. An easy fix would be grab some Techron concentrate for six bucks and go fill up with ethanol free and see if you still have the same issue.

 

And another idea and just taking a shot in the dark. Who changed the oil last? You or some shop? It could be overfilled and that could be a factor. I know when I was a newb I overfilled my car by a quart or so and it did exactly what you were describing. Also any change in oil brand or quality(Like going to high mileage) sometimes does this. I am very I tune to how oil effects all my cars and Mobil 1 regular seems to be the best. The more you go up in the chain of oil the more robust the add pack is and can bog down the engine and make it feel like you have an issue. In fact to be honest last oil change I switched to Castro’s Edge EP and my daily Honda Civic did EXACTLY what you car is doing. Switched it back to M1 and no issues at all.

 

Just throwing ideas that may help since the point is to get the car working quickly.

[Pleides]

This sounds like a fuel issue to me. Bad injectors, pump, fuel filter, etc.

[JoeInOregon]

This sounds like a fuel issue to me. Bad injectors, pump, fuel filter, etc.

Ya this sounds like an exaggerated version of the "stumble" people get when upgrading , and or removing the damper from the fuel system in the procces.....do these dampers ever fail...kinked or damaged fuel line under the manifold

 

Literally no worthwhile experience specific to this car but sure seems fuel related

 

Sent from my Pixel 3a using Tapatalk

[legacy200425]

Now here’s the question. What kind of plugs did you use? The fourth Gens hate Iridium plugs so that could be the culprit. Every time I change out my plugs someone always to be in the store complaining about their fourth gen GT or other model running like crap after they sold them iridium plugs.

 

Or the other culprit is the injectors. But those generally will throw a code of something is an issue.

 

By chance where do you live? Could be running like crap because of the winter blend fuel. An easy fix would be grab some Techron concentrate for six bucks and go fill up with ethanol free and see if you still have the same issue.

 

And another idea and just taking a shot in the dark. Who changed the oil last? You or some shop? It could be overfilled and that could be a factor. I know when I was a newb I overfilled my car by a quart or so and it did exactly what you were describing. Also any change in oil brand or quality(Like going to high mileage) sometimes does this. I am very I tune to how oil effects all my cars and Mobil 1 regular seems to be the best. The more you go up in the chain of oil the more robust the add pack is and can bog down the engine and make it feel like you have an issue. In fact to be honest last oil change I switched to Castro’s Edge EP and my daily Honda Civic did EXACTLY what you car is doing. Switched it back to M1 and no issues at all.

 

Just throwing ideas that may help since the point is to get the car working quickly.

 

 

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Hi,

 

i'm using NGK-PFR5B-11 those sparks are brand new. I dont think the problem is in gasoline, my friend has a 2.0 121kw 2006 and runs fine and we tank on the same gas station. I live in Czech Republic.

 

About the injectors i'm going to try liqui moly gasoline engine cleaner maybe it'll do something.

 

Oil has been changed recently by me, but i think its not overfilled (i still check that out) engine did the same thing before with old oil even when low on oil..

 

I tried to change the fuel pump just the pump not the whole assembly and that "filter sock" i guess i can try to remove that sock if it gets better or not. But if it would be fuel pump it would have bigger problems when driving or at higher rpms it would work or not ? Because once u take off it runs all fine.. You can cruise slightly above idle and no shaking or something like that..

Edited November 18, 2021 by legacy200425

[legacy200425]

Ya this sounds like an exaggerated version of the "stumble" people get when upgrading , and or removing the damper from the fuel system in the procces.....do these dampers ever fail...kinked or damaged fuel line under the manifold

 

Literally no worthwhile experience specific to this car but sure seems fuel related

 

Sent from my Pixel 3a using Tapatalk

 

Hi, well i try checking that out. I guess there isn't possibility to clean that damper if its clogged or something right ?

[MoleMan]

As far as the plugs you are spot on with the Platinum so that’s correct so I would not change that. As far as your fuel filter/pump I was thinking after I posted my prior response that could be the issue. I believe that part is a complete assembly only and I would just change out the entire part and not try to fiddle with just a certain component of the part. I had to change out a fuel pump a few years back in my daily Honda and I was thinking to myself the whole time I just paid $300 bucks for an entire assembly when I could have changed the filter for $20 bucks or less if the part was not integrated into the assembly. But then again any car Imhave had from 2006 and onward fuel filters are a whole assembly. Just another money grab from the manufacturer but nothing you can do about it. Personally I would not deal with aftermarket pumps and just pay the dealer what they want for the part.

 

Also thinking of something. Did you buy the plugs from a reputable shop? A lot of fake NGK and Denso plugs are being sold online that could produce an issue. Just an afterthought.

[apexi]

Is this a non-turbo? I've come to hate aftermarket coil packs and spark plug wires for non-turbos. The OEM coil pack has a grooves in each coil where the oem plug wires can snap into. Aftermarket wires and coils don't have that, and I think the plug boots can slip off. Not so sure that is your problem, but worth mentioning.

 

 

Did you install an aftermarket or oem maf sensor? If you still have your oem sensor, I'd try cleaning the resistors up inside the maf sensor, as shown in the attached picture. I think a lot of people incorrectly try to clean the temperature sensor because that's what's most visible.

 

 

Have you ever had a check engine light or any trouble codes in the past?

[MoleMan]

Is this a non-turbo? I've come to hate aftermarket coil packs and spark plug wires for non-turbos. The OEM coil pack has a grooves in each coil where the oem plug wires can snap into. Aftermarket wires and coils don't have that, and I think the plug boots can slip off. Not so sure that is your problem, but worth mentioning.

 

 

Did you install an aftermarket or oem maf sensor? If you still have your oem sensor, I'd try cleaning the resistors up inside the maf sensor, as shown in the attached picture. I think a lot of people incorrectly try to clean the temperature sensor because that's what's most visible.

 

 

Have you ever had a check engine light or any trouble codes in the past?

 

 

If the MAF was having an issue it should in theory throw a code. But good point as the OP stated they replaced the MAF it could just be a cheap replacement and causing the issue. I have personally seen a lot of Non-OEM MAFs cause the exact issues the OP is having.

 

I rarely use non oem parts anymore. In most cases they are the same price if not cheaper then some aftermarket brand. Sometimes however you pay through the nose for a part. But for me I do it right the first time instead of having to do it again which I have done in the past.

[SubOperator]

That long cold start time makes me think it's fueling. Either sock filter needs to be replaced, or pump harness connectors need to be cleaned, or both.

 

 

 

Probably easier to check the harness connector. Make sure the connector pins are clean and tight. IIRC there was someone here recently with similar fueling issue on GT, ended up being the connector.

[legacy200425]

As far as the plugs you are spot on with the Platinum so that’s correct so I would not change that. As far as your fuel filter/pump I was thinking after I posted my prior response that could be the issue. I believe that part is a complete assembly only and I would just change out the entire part and not try to fiddle with just a certain component of the part. I had to change out a fuel pump a few years back in my daily Honda and I was thinking to myself the whole time I just paid $300 bucks for an entire assembly when I could have changed the filter for $20 bucks or less if the part was not integrated into the assembly. But then again any car Imhave had from 2006 and onward fuel filters are a whole assembly. Just another money grab from the manufacturer but nothing you can do about it. Personally I would not deal with aftermarket pumps and just pay the dealer what they want for the part.

 

Also thinking of something. Did you buy the plugs from a reputable shop? A lot of fake NGK and Denso plugs are being sold online that could produce an issue. Just an afterthought.

 

Well thank you for your response. The problem is that if it wont be the pump then i spend fortune on that without fixing anything. Those NGK are straight from subaru.

[legacy200425]

That long cold start time makes me think it's fueling. Either sock filter needs to be replaced, or pump harness connectors need to be cleaned, or both.

 

 

 

Probably easier to check the harness connector. Make sure the connector pins are clean and tight. IIRC there was someone here recently with similar fueling issue on GT, ended up being the connector.

 

When i replaced the pump i tried to clean that sock with air and brake cleaner. I guess i can try to remove the sock and see what happens

[SubOperator]

When i replaced the pump i tried to clean that sock with air and brake cleaner. I guess i can try to remove the sock and see what happens

 

 

Look at the harness connector first. Easier to do before pulling the pump out from the gas tank.

[MoleMan]

Well thank you for your response. The problem is that if it wont be the pump then i spend fortune on that without fixing anything. Those NGK are straight from subaru.

 

So that solved the plug question.

 

What about the replacement fuel pump and the MAF? OEM from the dealer or aftermarket?

 

Any parts bought online that have the Subaru name yet are sold by a reseller not an Authorized dealer? Just asking not to harp on you but its something I see alot when buying replacement parts for my Honda is fake parts that look identical to OEM but the packaging is just off slightly so they look authentic.

Edited November 19, 2021 by MoleMan

[All_talk]

It does sound fuel related, I would not continue to through parts and guesses at it... measure the fuel pressure. Tee in a test gauge between the fuel damper and the connection at the manifold. I have run the hose out the back of the hood and held the gauge face down to the windshield with the wiper, so I could see it as I drive. If the pressure is good you can rule out pump and filter issues.

[legacy200425]

It does sound fuel related, I would not continue to through parts and guesses at it... measure the fuel pressure. Tee in a test gauge between the fuel damper and the connection at the manifold. I have run the hose out the back of the hood and held the gauge face down to the windshield with the wiper, so I could see it as I drive. If the pressure is good you can rule out pump and filter issues.

 

Hi, damn awesome idea. I'll try to get the fuel pressure gauge and check that out.

[legacy200425]

It does sound fuel related, I would not continue to through parts and guesses at it... measure the fuel pressure. Tee in a test gauge between the fuel damper and the connection at the manifold. I have run the hose out the back of the hood and held the gauge face down to the windshield with the wiper, so I could see it as I drive. If the pressure is good you can rule out pump and filter issues.

 

 

Hello, today i tried to check the fuel pressure like u said and it seems all fine its within the range. no drops or something like that.

 

I kinda forgot to mention that in that car there's also and LPG, the problem is that the LPG is not working atm. Service told me that all 4 injectors are bad and needs to be replaced + reducer. I didnt mention the lpg because i didnt think it would be somehow related to this issues.. Since it should run fine when the lpg is turned off right ?

[Paycheck]

Hi there...

 

I figured I would chime in with my own similar issue. Hoping to find some glimmer of hope of coming up with a solution. Last post in the thread below is a summary of everything I've seen/tried over the last several years. OP, let me know if this sounds like what you've seen on your own car.

 

https://legacygt.com/forums/showthread.php/removing-05-gt-camshaft-position-sensor-p0340-263392p3.html

 

Thanks,

$$$

[legacy200425]

So thanks everyone for help. I finally solved the mystery.

 

The issues with "hesitation" was a god damm valve cover gasket

 

I noticed that drivers side was leaking quite a bit.. So i decided to change that gasket but when i removed both covers i also checked valve clearence which was bad.. so i did the valve adjustment then replaced the gasket on drivers side. When i put that back together it was a brand new car for a week or so.. then the hesitation was back. So i also did the passenger's side and and hesitation is gone and its all fine now.

 

The second problem was just my stupidity, it was cuz of bad battery.. when i got the car i checked the battery and it seemed fine.. it had like 12.4V i think and the starter was rotating fine i thought.. but i tried to measure the battery while starting and voltage has significally dropped with different battery there wasnt such a huge drop in voltage and car started right up even in very colt temperature.

 

Perhabs this will help to someone..

[Tehnation]

Now here’s the question. What kind of plugs did you use? The fourth Gens hate Iridium plugs so that could be the culprit. Every time I change out my plugs someone always to be in the store complaining about their fourth gen GT or other model running like crap after they sold them iridium plugs.

 

Or the other culprit is the injectors. But those generally will throw a code of something is an issue.

 

By chance where do you live? Could be running like crap because of the winter blend fuel. An easy fix would be grab some Techron concentrate for six bucks and go fill up with ethanol free and see if you still have the same issue.

 

And another idea and just taking a shot in the dark. Who changed the oil last? You or some shop? It could be overfilled and that could be a factor. I know when I was a newb I overfilled my car by a quart or so and it did exactly what you were describing. Also any change in oil brand or quality(Like going to high mileage) sometimes does this. I am very I tune to how oil effects all my cars and Mobil 1 regular seems to be the best. The more you go up in the chain of oil the more robust the add pack is and can bog down the engine and make it feel like you have an issue. In fact to be honest last oil change I switched to Castro’s Edge EP and my daily Honda Civic did EXACTLY what you car is doing. Switched it back to M1 and no issues at all.

 

Just throwing ideas that may help since the point is to get the car working quickly.

 

Wait! Our cars hate iridium plugs? When did this happen? Iridium is oem, and the ngk iridiums is pretty much what like every person on this site uses lol. Where did you get this information?

[Infosecdad]

Agreed, I've only used NGX Iridium plugs and have had zero issues.

 

Can you point to where "4th gen's hate iridium" because I haven't seen that before in the last five years of being on this forum.

[NORULZleggy]

Agreed, I've only used NGX Iridium plugs and have had zero issues.

 

Can you point to where "4th gen's hate iridium" because I haven't seen that before in the last five years of being on this forum.

 

I have been using Iridium for the past 9 years no issues. have them on this 06 LGT fresh build and the car is great.