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Amedee, Subaru Technician
Category: Subaru
Satisfied Customers: 26451
Experience:  ASE Technician advanced level specialist. Wisconsin certified emissions state inspector
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Subaru Forester: misfire..the cylinder #3..rain..ignition coil

Resolved Question:

Car: Subaru Forester 2006.Problem - misfire in the cylinder #3 after a 2-3 day of a moderate rain.We already replaced spark plugs, wires and ignition coil. The problem is still there. My mechanic suspects a computer - the problem with contacts. I was looking under the hood and wondering if moisture can get in between the contacts in the cable connector that connects the sensors to the computer?
Submitted: 6 years ago.
Category: Subaru
Expert:  Amedee replied 6 years ago.
Hello and Welcome to Just Answer. My name is XXXXX XXXXX I will try my best to assist you and your 100% satisfaction is my goal. I have been working on these vehicles for over 10 years so I am very familiar with this system and how they work. However, keep in mind, that I need some solid concrete facts/evidence/clues from you in order to give you a good answer about your vehicle. Please realize that all my answers are based solely on the info that you provide me with.

When does the engine misfire? At idle or just under a load?

Do you know what the engine vacuum is at idle or just when it misfires?
Customer: replied 6 years ago.
When my wife started a car, it was running roughly. As she pulled out of the driveway, the check engine light started blinking. After a short while it turned off, and then both, check engine was steady on and cruise control light started blinking.

Later that day, I disconnected the battery, the lights reset (became off) and they was not on since. I cannot tell you anything about the engine vacuum unless you tell me how to measure it.
Expert:  Amedee replied 6 years ago.
Have you tried any injector cleaner? A lot of times the injector cleaner will clean this type of problem up. There are two ways injector cleaner works. 1 put in the gas tank and let it run through the whole system. It will clear the fuel filter strainer in the tank, the external fuel filter, the lines and last the injectors as it enters the engine. (This may take a few days). Or 2, hook it up to manifold vacuum (a vacuum hose) and let the vacuum suck it in the engine. There is a special tool that is used for this and is rec strongly. (But if u are careful one can accomplish this without a special tool). This method of entering the engine through vacuum cleans the back on the valve extremely well. The back of the valve is where the carbon builds up and when the injector sprays the gas will get absorbed in the carbon instead of going in the cylinder. This will then cause a performance issue. Both of the methods are very important will work very well and both will definitely help on gas mileage! If this running problem is the injector and this does not clean up the running issue injector replacement may be necessary.
Expert:  Amedee replied 6 years ago.
Also, before i forget, there is a TSB out for a misfire condition. According to the TSB, the fix is a ECM re flash.

Also, last but not least, lets not forget about an engine mechanical problem. Sometimes a valve can stick open causing the cylinder to misfire..
Customer: replied 6 years ago.
I can try to clean the injectors (and I did it by adding the cleaner to the tank, but I did not do the vacuum sucking onthis car), I have done this with Seafoam on another car.
Real question i have: why does it happen after a few days of rain? I have an impression that water condensates somewhere and causes the problem. Could it be a fuel injector? Probably.

As of ECM, we did reflash it recently, there was a recall. But the problem continues.
Anyway, let me try the Seafoam, and if it does not work, we will try replacing the fuel injector.
Customer: replied 6 years ago.
also what is the tool for cleaning via mainfold vacuum?
Expert:  Amedee replied 6 years ago.

Sorry for the delay!


There are a few tools.. depending on how you want to clean the intake will depend on which tool you are going to want to buy. They make a fuel injector cleaner kit that would be a good idea to get.


Usually ignition components are affected by rain or moisture. However, it could be the crank sensor, engine mechanical or yes.. a bad leaky, stuck injector.

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