[Marana]

My 2015 Forester XT only at 43k miles and its summer throughout the year around 90F

Last few weeks my cold start is getting worst. When I start, the engine idle rough, I can hear misfire and the annoying knocking/clicking sound that is random and doesn't seems to have a pattern.

Here is the link to the cold start and you can hear those knocking or clicking sound.

Funny is when the car hit around 104F or blue light went off, the rough idle is gone, clicking sound is gone and there is no misfire. Throughout the day everything drives fine.

There is no error light showing at all.

Any help will be great!

Thanks

 

[hengyu408]

Have you done anything to the car recently? Might be a bad tank of gas.

 

[Marana]

Nothing has been done to the car. It's stock.

The sound is high pitch and coming from the left side near where the battery location.

I went to my friend who told me could be faulty fuel injector/s.

Would like to know if any forester xt owner encounter such issues.

 

[Pursuit]

Mine does this as well, as does a friend's WRX with the same motor. This is normal, at start up the ECU runs the high pressure fuel pump (the whining noise you hear) and high rpm to heat up the catalytic converter, as the cat quickly starts to get up to operating temp there are mini combustion explosions of the unburnt fuel hitting the cat (the knocking noise you hear). If it's worse recently than in the past, you may also be getting bad gas or air filter may be clogged. This time of year condensation can build up in motor as well and contribute to the cat behavior described above as well, esp if PCV is sticking open.

 

[dentinhe]

Mine was doing something like that as well, I ended up taking it to the dealership for service. It was getting carbon buildup in the top end of the motor. They tore it apart and cleaned up the inside and reassembled it under warranty. They had it 6 weeks, said they had to talk to the Subaru engineers. I did get a free loaner and put 7,000 miles on it.

 

[MNTNDRMNGFXT]

Six weeks?! That's a huge amount of time. I'm surprised it took them that long.

 

[karlaudi]

So, all things being equal, the trouble lies in the cold start system it would appear. Not being familiar with the exact design, I would pay Subaru and download the Factory Service manual from their website to learn what is in the cold start circuit of the ignition and fuel injection systems and intake manifold and how they work exactly.

It would seem that you are not getting fuel enrichment needed to start a cold motor. Think the fuel injection version of a carburetor choke, since the problem goes away when the engine is at operating temperature. So depending on the design it could be one or more of the following, or something else Subaru uses for cold start operation:

A failed temperature sensor and / or its wiring

A failed cold start fuel injector and / or its wiring (if used)

A failed auxiliary air valve or idle speed motor / valve and / or its wiring (if used)

A cracked , broken, or disconnected air hose, pipe, or other item used during cold start that is allowing air to enter the engine below the throttle plate.

And so on...


The clicking sound could be the fuel injectors and when the engine is running normal the sound is muffled or it is from a component that is used during cold start. Hard to know exactly without being there. The sound you are referencing in the link sounds like a loose component banging from a rough idling motor, but it really is hard to tell for sure without being there or having a visual reference.

 

[Scooby24]

I would guess you've got a serious injector problem.

Are you still under powertrain warranty? I'd get it in ASAP.

 

[Marana]

Good Morning All,

Thanks for all the reply.

Just some update from my side.

I was advise to use Fuel Injectors cleaner to run the car for at least 2 tank to see if it does improve the problem I face during cold start.
But after two weeks and 2 round of using the fuel injector cleaner it didn't improve. The two cleaner I use is Fuel Doctors and Amsoil PI.

It just get worst day by day. The cold start behave like the following;

The car didn't want to start first time. On the second try, the car start but the rpm is jumping around the 500 - 700 rpm and it stay there for a good 4-5 sec before it shoot up to the 1500rpm and the rpm jump up and down (I guess this is call misfire)

The car still have the random ticking/clicking sound and the engine vibration is not normal.

Once the engine is up to temperature at (70c or 158f), the rpm settle down to around 700rpm but you do randomly ticking of the needle which indicate some sort of misfire.

At the beginning injectors were thought to be faulty. This was verify by the mechanic as all 4 of them is working normally. So we rule out the injectors.

Im still waiting for the mechanic to update me the status of the car.

 

[Marana]

Mine was doing something like that as well, I ended up taking it to the dealership for service. It was getting carbon buildup in the top end of the motor. They tore it apart and cleaned up the inside and reassembled it under warranty. They had it 6 weeks, said they had to talk to the Subaru engineers. I did get a free loaner and put 7,000 miles on it.

Hi dentinhe,

So you saying it is all cause by the carbon buildup?

 

[Scooby24]

Next I'd check spark. One new coilpack can be rotated around.

 

[Marana]

Hi Scooby24,

I've changed the spark plug. The coilpack and injectors also checked. All is fine

 

[Scooby24]

Ran crc intake valve cleaner?

 

[Marana]

This I have yet to perform. Actually the car never did any cleaning for the build up of carbon. Will try to use the cleaner to have a try.

 

[Andrewfscn]

@Marana is there any update after using crc cleaner?

 

[dentinhe]

Carbon build up is what I was told? The dealership told me they tried it a few times because they had to run it through a cold engine. So it does seem it’s something from start up causing the problems. I have had the series of lights on the dash light up again, set up an appointment with the dealership and they went off on their own. I don’t run premium fuel like they “recommend but don’t require “ but I have been using Lucas brand fuel injector cleaner about once a month, and no more problems. I hope this helps?

 

[Corn]

One might consider when using these injector cleaners and these upper engine cleaners which are applied to intake manifold. First the injector cleaners which are applied to fuel. When I was comparing the instructions on those I noticed that some of them say that in some cases it should be applied to little by little and not the whole bottle to full tank. I don't remember the exact wording though. That makes sense if you think about the DI fuel system. It has high pressure fuel pump which is more critical to lubrication than low pressure port injection system. How much more wear you're causing to the high pressure pump when using these fuel injector cleaners and whether it will ever cause problems to your pump I can't tell. But it made me having second thought about those and chose not to buy it.

Next is the upper engine cleaners that are applied to the intake manifold. When I pulled my o2 sensor out after using the upper engine cleaner it was gunked with oily residue. You might get cleaner valves and maybe piston head but are moving the problem to O2 sensors and catalytic converter? My point is, some might not consider the side effects these things might cause.

 

[slothman]

How much more wear you're causing to the high pressure pump when using these fuel injector cleaners and whether it will ever cause problems to your pump I can't tell.

...You might get cleaner valves and maybe piston head but are moving the problem to O2 sensors and catalytic converter? My point is, some might not consider the side effects these things might cause.

In Australia Subaru require the application of its own brand fuel additive and upper cylinder cleaner at every service, or 6,000 km. Neither seem to be causing any issues. I'm guessing the chemicals are much the same as those found in other brands, and in the case of the fuel additive as found in high detergent premium fuels. Fwiw, Subaru UK recommends Techron fuel additive.

 

[Marana]

@Marana is there any update after using crc cleaner?

Sorry for the late reply Andrew, It doesn't seem to make any difference but as of now, the main issue kinda focus on the fuel pump and the fuel filter.

The reason why is that when the petrol left around 30%, the cold start will have those random knocking and misfire. Whereas if the petrol tank is above the 30% level, the cold start is completely fine.

 

[Marana]

Mine does this as well, as does a friend's WRX with the same motor. This is normal, at start up the ECU runs the high pressure fuel pump (the whining noise you hear) and high rpm to heat up the catalytic converter, as the cat quickly starts to get up to operating temp there are mini combustion explosions of the unburnt fuel hitting the cat (the knocking noise you hear). If it's worse recently than in the past, you may also be getting bad gas or air filter may be clogged. This time of year condensation can build up in motor as well and contribute to the cat behavior described above as well, esp if PCV is sticking open.

@Pursuit

Thanks for the info, I hope is the bad gas and I changed the air filter which might have indirectly cause the issue but it does helps to improve the fuel mileage.