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2004 Forester Stuttering,Sputtering, and Hesitating when hard on the throttle


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2004 Forester XS 5-speed

107,000 Miles

500 miles on new oil and filter

500 miles on new K&N air filter

Rough idle was cured with seafoam approximately 2000 miles ago

 

My car has always run great and has given me no problems in the year I've owned it. I've put a lot of miles on (20,000+) but I have kept up with the maintenance religiously. It did start idling a little rough a few months ago and I gave it a full seafoam treatment last month (2000 miles ago). That is the only thing I have done out of the ordinary and everything has been kosher since.

 

This past week I got an oil change and installed a new air filter then drove 500ish miles from Pennsylvania to Vermont without incident. When I left Vermont to come home, I got about 30 miles down the road and the car started stuttering and hesistating when I'd get on the throttle hard. I figured, it might be a fuel filter so I picked one up and AutoZone and swapped it in the parking lot. I also put a bottle of seafoam in the fuel tank in case I had a gunky injector.

 

Even after swapping the filter, the problem persists. It idles great and runs totally fine at any RPM, but if the engine gets under too much load, like accelerating or maintaining speed up a hill, it starts stuttering and cutting in and out. It hasn't stalled yet, despite me going pretty hard on it a few times just to see what would happen.

 

It runs well enough that I made the 500+ mile drive home just fine, it was just annoying to pass people or go up big hills.

 

Anyone have any idea what's going on? I am completely at a loss and would love some advice.

Edited by jmoss5723
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Is the engine cutting out entirely for a second or is it just the power delivery dropping way off and on quickly?

If the latter: When was the last time your knock sensor was changed? Mine flaked out on me without setting a check engine light and was causing all kinds of bucking and hesitation under load.

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If your car has a MAF sensor the oil from the K&N has worked its way onto the sensor element and "clogged" it. It will need to be cleaned with MAF sensor cleaner and the K&N replaced with a regular paper filter.

You may also need to clean the intake piping and filter box to remove any excess oil to prevent a recurrence.

 

If no MAF sensor, change the spark plugs and wires. Even if you don't have a CEL on this sounds like typical misfire under load symptoms due to old spark plugs.

 

Knock sensor is easy to check and can cause this type of issue as well.

Search for my Knock sensor 101 thread for specifics on locating, inspecting, and changing the knock sensor.

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Is the engine cutting out entirely for a second or is it just the power delivery dropping way off and on quickly?

 

If the latter: When was the last time your knock sensor was changed? Mine flaked out on me without setting a check engine light and was causing all kinds of bucking and hesitation under load.

 

Definitely the latter. Knock sensor will be my next check. Thanks for the advice.

 

If your car has a MAF sensor the oil from the K&N has worked its way onto the sensor element and "clogged" it. It will need to be cleaned with MAF sensor cleaner and the K&N replaced with a regular paper filter.

You may also need to clean the intake piping and filter box to remove any excess oil to prevent a recurrence.

 

If no MAF sensor, change the spark plugs and wires. Even if you don't have a CEL on this sounds like typical misfire under load symptoms due to old spark plugs.

 

Knock sensor is easy to check and can cause this type of issue as well.

Search for my Knock sensor 101 thread for specifics on locating, inspecting, and changing the knock sensor.

I do not have a MAF, I have a MAP. So maybe spark plugs are the issue? Would that start acting up all of the sudden like that? I would figure that would be a gradual progression.

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You might scan for 'pending' codes after the next time it happens. Wondering if a bad spot on the TPS could do this too.

 

I THINK you have a larger 'cap' on your fuel pump with a sort-of strainer/filter in side. While 2000-2003 legacy and Outback models have had problems in that area with a small cap and o-ring being compromised (and shutting cars down completely), the issue has never been reported in 04 . Maybe the Forester Forum would know for certain. You can get the cap and filter on-line, dunno about just the filter.

 

Frankly, I think you have other things to check before the fuel pump but, I suppose I mentioned the above because it's a remote possibility.

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Went to Advanced Auto to investigate my check engine light (its always on because of an evap leak, so I check it periodically for other codes) I have a misfire on cylinders 1 and 2 which are front passenger and front driver, respectively.

 

I decided to check compression and plugs/wires first. I disconnected the wire to the plug for cylinder 1 and I was met with LOTS of dirty oil all over the rubber hood for the plug. OH NOOOO!!! I crawled underneath and found some more oil.

 

BAD HEAD GASKETS!!!!! :eek:  :mad:

 

My oil is clean and my coolant looks good, so i don't think I'm mixing fluids, just losing oil and sending it places it doesn't belong. Off to the stealership. I needed the timing belt done anyways....

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Went to Advanced Auto to investigate my check engine light (its always on because of an evap leak, so I check it periodically for other codes) I have a misfire on cylinders 1 and 2 which are front passenger and front driver, respectively.

 

I decided to check compression and plugs/wires first. I disconnected the wire to the plug for cylinder 1 and I was met with LOTS of dirty oil all over the rubber hood for the plug. OH NOOOO!!! I crawled underneath and found some more oil.

 

BAD HEAD GASKETS!!!!! :eek:  :mad:

 

My oil is clean and my coolant looks good, so i don't think I'm mixing fluids, just losing oil and sending it places it doesn't belong. Off to the stealership. I needed the timing belt done anyways....

 

Uh, what you found is most likely due to leaking VALVE COVER and spark plug tube gaskets.

 

not saying you might not also have leaking head gaskets....just, it's common for older soobs to have oil in the plug tubes.

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the heads are the first thing to leak have done six in a row all leaking oil into the plugs and leaking down from the head seam right above the oil fillter and on the back ds rear coner of head none were over 160000kms the head gaskets go before even the alt belt or battery wears out. Anyway worth checking I find is no point doing any work on engine unless your taking it right out to do full reseal or you end up going right back in to tear it down agian

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the heads are the first thing to leak have done six in a row all leaking oil into the plugs and leaking down from the head seam right above the oil fillter and on the back ds rear coner of head none were over 160000kms the head gaskets go before even the alt belt or battery wears out. Anyway worth checking I find is no point doing any work on engine unless your taking it right out to do full reseal or you end up going right back in to tear it down agian

 

You just named every place that I am leaking oil. And I have about 170,000km.

 

I wish I had noticed sooner, but my oil pan gasket was leaking AND my oil pan had a hole rusted through it. This made the whole underside of my car fairly oil all the time, and I didn't notice the more expensive leaks.

 

On the bright side, I've got very little rust on my undercarriage  :lol:

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Anyone have an opinion on driving the car like this?

 

I had (have?) misfires on cylinders 1 and 2 (front passenger and front driver, respectively) and it is obviously leaking some oil. However it is not overheating, mixing coolant and oil, or losing any coolant. If I don't ask it for much power (easy up hills and minimal passing) it feels like its running fine. I have another car that I can drive daily, but I have to drive this thing 130 miles to the closest shop I'd trust.

 

I've put 500+ miles on it since it started showing symptoms.

 

Thoughts?

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well, you need to get the misfiring under control. No good will come from driving a car regularly misfiring. Tough on some parts including the cat converter.

 

As for leaking, LOTS of cars are driven with leaks and, while less than ideal, if you keep it topped off, and maybe clean the oil off occasionally, that isn't a big deal.

Edited by 1 Lucky Texan
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well, you need to get the misfiring under control. No good will come from driving a car regularly misfiring. Tough on some parts including the cat converter.

 

As for leaking, LOTS of cars are driven with leaks and, while less than ideal, if you keep it topped off, and maybe clean the oil off occasionally, that isn't a big deal.

I'm not worried about the oil leaks, mostly the misfires. I was figuring that it was misfiring because of the oil being in places it should not be...?

 

My other concern is how high is the risk that I will start mixing oil and coolant or overheating? LIke I said, it is not doing these things yet, but I'm afraid it might. Is it likely enough that I should even worry about it?

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I'm not worried about the oil leaks, mostly the misfires. I was figuring that it was misfiring because of the oil being in places it should not be...?

 

My other concern is how high is the risk that I will start mixing oil and coolant or overheating? LIke I said, it is not doing these things yet, but I'm afraid it might. Is it likely enough that I should even worry about it?

 

 

Maybe someone could suggest a shop near you in PA that could help determine what work must be done now, what you need to save up for in the future, and what you could live with. Is there evidence now of coolant in the crankcase? perhaps sending a sample off for oil analysis is a good idea. Is there combustion gasses in the coolant? That's not good either. BUT, if you are just weeping/dripping oil and coolant externally, that might be manageable. Top-off the oil every tankful or every second tankful of gas - as needed, try the Subaru 'conditioner' in the coolant to slow down the weeping. get the valve cover gaskets changed to stop the misfiring. that 'might' be all that's needed.

 

you just need good diagnosis.

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External oil leaks do not mean it is leaking coolant.

I still think you should clean the area and check again for leaks every few days, or every day if you can.

 

If the head gaskets actually are leaking now is the time to replace them since you're due for a timing belt.

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Did heads on a 02 legacy 220000kms had burnt a path past the cly and had worn a spot about 3 thow into the head they will run like thiss for long time the owner said it started overheating at 170000kms so lasted a bit but defanatly did damage to head bottom end was ok. I have been telling customers 155000 is the magic number right before its first timing belt i pull engine do full reseal headgaskets and wp and timing belt idlers ect

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External oil leaks do not mean it is leaking coolant.

I still think you should clean the area and check again for leaks every few days, or every day if you can.

 

If the head gaskets actually are leaking now is the time to replace them since you're due for a timing belt.

 

Did heads on a 02 legacy 220000kms had burnt a path past the cly and had worn a spot about 3 thow into the head they will run like thiss for long time the owner said it started overheating at 170000kms so lasted a bit but defanatly did damage to head bottom end was ok. I have been telling customers 155000 is the magic number right before its first timing belt i pull engine do full reseal headgaskets and wp and timing belt idlers ect

 I'm getting it all done.

 

Timing belt is actually a little bit overdue, head gaskets are definitely bad, and valve cover gasket is leaking. Getting it all done at once and it should be all better for another 100,000+

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