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2003 Forester MT
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36 Posts
Discussion Starter · #1 ·
Hey everyone!

I’ve got a 2003 forester X EJ25 5 speed with 241,000 miles. The problem I’m having is that my CEL comes on and says that all 4 cylinders are misfiring. The CEL will blink sometimes (I know it’s bad for the cats. Lol) but it goes away after a second and then stays on.
I’ve changed all the plugs with NGK and wires are NGK as well, new ignition coil (OEM), new valve cover gaskets, and tube seals, new fuel filter, pump and strainer and a new ECT sensor to fix the fans that wouldn’t come on. Also both o2 sensors have been replaced. The car runs great and has no lack of power but does have a slight vibration when cruising in 5th gear. I’m at a loss and could use any help at all at this point. 😭😭😭
 

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2012 SH Manual Diesel
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854 Posts
Is your timing belt replacement up to date?

Is misfire detected from Knock sensors, or Cam and Crank sensors?

Check, and test the sensors; also making sure they are seated correctly. Make sure connectors are clean and serviceable; and wiring harness is intact; and showing the correct continuity, voltage or resistance etc.
 

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2003 Forester MT
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36 Posts
Discussion Starter · #5 ·
Yes, all wires go to the correct cylinders. The thing is the car runs great, I have no lack of power and it doesn’t feel like there is any sort of miss. But the codes still persist.
 

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1999 A/T - 235,000 mi. WA state
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1,011 Posts
So, let's restate this:
The thing is the car runs great, I have no lack of power and it doesn’t feel like there is any sort of miss. But the CEL still comes on
You won't appreciate my saying this, perhaps, but my approach would be two step.
1) Cut a 1" square piece of black electricians tape (can't see thru this; removable easily) and place it over the CEL to block from view,
2) Continue driving just as you have. In time the problem will either go away or present itself in another way.

I was in a car pool with a former mechanic and he commented on an occasional engine miss in my car; I told him what I'd looked for unsuccessfully and that I was going to drive until it eventually showed me what the problem was in no uncertain terms. He laughed and said that's a good practical approach, but he'd usually been able to get repair work out of the fear/uncertainty approach with others. :)
 

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2003 Forester MT
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36 Posts
Discussion Starter · #8 ·
Well, update. I was merging onto the highway and I had a sudden loss of power and my CEL started blinking constantly. I pulled over and the car died. The car will start back up with a little bit of throttle and then idle super rough. Even at idle the CEL will still flash. The codes are still p0301 p0302 p0303 and p0304. There is also a very strong smell of gas coming from the exhaust. I checked the timing and it’s still spot on. I’m out of ideas at this point and will take any suggestions. PLEASE HELP. o_O
 

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2003 Forester MT
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36 Posts
Discussion Starter · #10 ·
I checked the engines timing. I took off the front cover, inspected belt to see if it had jumped any teeth and the timing is spot on still, and the belt is still in decent shape as well.
 

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2003 Forester MT
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36 Posts
Discussion Starter · #12 ·
Yes, the coil pack doesn’t have any cracks in it and I misted it with water to look for arching. I also replaced the coil pack with a known good one and there was no change. I’m honestly wondering if I may have dropped a valve or something else mechanically is wrong because the entire ignition system is new, and the only parts of the fuel system that haven’t been replaced are the injectors, the fuel pressure regulator and the fuel line damper.
 

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2012 SH Manual Diesel
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854 Posts
Since ECU reports all 4 cylinders misfiring, maybe start with the shared common component(s); the engine ground; power supply to injectors; main relay and fuse; crank sensor; engine wiring harness; and ECU. Although not impossible, it’s probably less common for all four cylinders to independently develop the same issues, at the exact same time (usually 1, or a bank of 2, and then gradually others may follow).

With any luck, it might be one of the first 3, or the forth in the list (but don’t overlook the fact, that there could be more than one component involved, especially on a higher mileage car). However, since the ECU was originally detecting the misfire, but the engine itself was initially running fine (no physical rough running/power loss symptoms), I might initially suspect the crank sensor (or associated wiring harness) to be the culprit.

During the recent incident that you reported (loss of power, stall, rough idle etc), the ECU may have detected a dangerous condition, and retarded all parameters to protect the engine, or put the engine in ‘limp mode’.

Still consider, if the timing belt; tensioner; water pump etc.; should be replaced, as a matter of precaution. As it would be a shame; for you to have replaced all the ignition, and fuel system components; along with all your time and effort in diagnosing the issue; to then suffer a major component failure.
 

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2003 Forester MT
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36 Posts
Discussion Starter · #15 ·
Also, does anyone know how to go about testing the fuel pressure regulator? I’ve tried searching everywhere but can’t come up with anything.
 

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2007 Forester Sports XT 4EAT
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