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Old 04-14-2005, 10:58 AM   #1
b5o5m5b
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Exclamation Intermitent Power Loss at all RPMs MY00-2.5RS-MT

I've got a wierd one for you guys. I'm getting intermitent power loss at all RPM. I've been noticing it for the last few months but now it's made the car undrivable.

It's most noticible when I'm driving at highway speeds. The car will be running just fine, but then for a breif second it will loss all power (kinda like it's run out of gas or something) but as soon as it's gone the power will come back. It started doing this rarely, but in the last few weeks it happens more offten (like two or three times every 10mins). Sometimes I would get a CEL, sometimes not. When I did read the CELs it was reporting misfires on all four cylinders.

The car has 80.000 miles on it. It had the original plugs and wires up unitl last weekend when I changed them in an attempt to fix this problem. I havn't seen any CEL misfires since the plug/wire change but it still runs poorly. I've also replaced the fuel filter with no change.

This morning, a letting the car warm up (a rare thing for me) it was idling VERY bad. It sounded like revs were bouncing up and down from 300-700RPM. When I got in the car I noticed the CEL was flashing, so I shut-off the engine, let it sit for a few seconds, and restarted it.

I tried to drive it down the block, but but had very low power and backfiring trying to accelerate from a stop, when shifting to second, and going into third. At that point I turned around and brought the car back home, becasue I didn't want to risk possible damage.

I'm going to start looking at the injectors this evening when I get home.

I'm not sure if there are any Subie Mechanics on the list, but if anyone has a suggestion I'd like to hear it.

Thanks,
Derek.
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Old 04-14-2005, 11:23 AM   #2
holland_patrick
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Need a new Cat???? my jeep had that problem.. If you feel adventrous make a cut in the pipe just befor your cat and if you get your power back that's it if not patch the small whole up with that putty stuff.
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Old 04-14-2005, 12:30 PM   #3
b5o5m5b
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Yeah... I would think cat too if it was a more consistant lose of power, but 95% of the time it runs just fine. The sputturing and kicking seems to occur at any speed/RPM combination.

I should also mention that I have a Stromberg cat-back exhaust and K&N airfilter (which I just cleaned 3mos ago).

Derek.
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Old 04-14-2005, 12:38 PM   #4
SOLUTION
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I'd suggest the front O2 sensor and the knock sensor. I had the same problems before in my 2000 RS.
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Old 04-14-2005, 01:56 PM   #5
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experienced it before too. traced it to a loose connection for the MAP sensors.
either that or possibly faulty map sensors.
u might want to check it out.
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Old 04-14-2005, 02:49 PM   #6
b5o5m5b
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Thanks for the tips everyone...

Is there a test I can perform on the MAP or knock sensors to see if they're faulty? Maybe pull the wiring plugs and check for a certain impedence with an ohm meter?

Derek.
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Old 04-14-2005, 04:49 PM   #7
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How is your clutch holding up? I remember when I owned a 5 spd honda civic, driving on the hwy I had intermitten loss of power. I asked a buddy of mine and he said it was the clutch slipping. We changed the clutch (clutch was pretty low, almost to the the screws) and everything was fine after that.
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Old 04-14-2005, 10:31 PM   #8
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A clutch isn't going to cause a CEL or misfires.......

Look into a new coil or ignitor.

Jay Storm
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Old 04-14-2005, 10:36 PM   #9
Tim Sanderson
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Is the whole car dropping out? Like the everything electrical?

I think Storm is on the right track.
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Old 04-15-2005, 12:02 AM   #10
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you may also want to check your alternator...may be an o2 sensor as someone else mentioned
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Old 04-15-2005, 01:03 AM   #11
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Electrical or sensor related. Since it's all/nothing, it not, say a single plug wire. I would:

Check all ground wires. Take em off, clean em, put em back on.
Check all sensor plugs. Take em off, clean em, put em back on.
Check coilpack, and all plugs.
Do a grounding mod.
Use dielectric grease where appropriate.

Should take two hours tops to do everything. If you still have an issue, it's probably a bad sensor (e.g. MAP) or coilpack.
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Old 04-15-2005, 07:05 AM   #12
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What spark plugs did you use and did you use OEM plug wires?
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Old 04-15-2005, 08:52 AM   #13
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id check int his order because of cost, but it is most likely your front oxygen sensor

plugs + wires
Fuel filter
Pcv
front 02
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Old 04-15-2005, 09:00 AM   #14
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Hesitation/loss of power and I automatically start thinking something electrical and related to the combustion process.

Look at the plugs/wires/coil pack (bet problem is related to this)
O2 sensor (front mainly) how has the gas mileage been? Horrible gas mileage will point towards an O2 sensor malfunction
MAP sensor (check to make sure it is on tight)

My sister had the same issue with her '97 Rally Sport, where it was throwing lots of CEL's, and basically undrivable. Brought it to a mechanic, pulled CEL's and then found it was a bad coil pack and wires. Had them replaced as well as the spark plugs and it ran like new.

I'm pretty sure you'll find your problem with that part of the engine. Check the coil pack and check to make sure the wires are making good contact with the pack.

AJ
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Old 04-15-2005, 03:51 PM   #15
b5o5m5b
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Wow... Lots of good suggestions here. Thanks again...

It was asked which plugs and wires I used, I installed Bosch wires (they were a perfect match for what I took off) and Bosch Plat. plugs (the ones with only a single ground electrode).

I drove the car a few miles over to my dads to work on it in his garage and noticed that it seemed to start running worse as the engine warmed up (based on the dash temp guage). The CEL came on after a few minutes of driving and a really bad start from the first stop sign. When I got it in the garage I hooked up a SnapOn code reader to check the CELs. I had a misfire reported on all four cylinders and 'bank #1 too rich'. I cleared these after writing them down.

While it was hooked to the reader I monitored the MAP and didn't see anything odd. It reported a nominal reading from idle to 3000rpm. The fuel system was moving from open loop to closed loop as it should. Coolant temps were also reporting nominal.

It's been suggested by another mechanic that a throttle body cleaning may be needed so I'm thinking of using a professional grade cleaning kit from Valvoline (the kind that requirse a special hose and hookups to a vacuum port on the throttle body).But I think I'll clean and check all of the connectors before I go any further with this.

I'm also starting to lean towards the O2 sensor because of the many suggestions from this thread. I'll take a closer look at the readings I can get from the computer to see if I can find an anomily. I hope I just missed it last night and it will jump out at me this evening.

Thanks again to everyone for their input. I'll keep you posted,
Derek.
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Old 04-15-2005, 06:28 PM   #16
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So, let's get this straight... you changed the spark plug wires / plugs and started getting misfire? If so, is there any need to state the obvious?
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Old 04-18-2005, 09:38 AM   #17
b5o5m5b
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Yeah... that was the obvious and that's why I already checked it before posting to the list. The plugs and wires are all seated well.

I also tested compression when I double checked the plugs and that looked good.

I monitored the engine on my drive into work today and noticed the long term fuel trim seemed rather high at -27.3% (does anyone know the typical range?)

I also noticed that it would when the LT trim was reporting -27 the short term trim would hover around 0 (+/- 4 to 5%). But when the revs hit around 3700 things would change, the LT trim would drop to 0 then the ST trim would try and compensate and shoot up to the -20 range and I'd feel a slight boost in power. Then when it switches back (so the LT is at -27 and the ST is around 0) I feel the hesitation.

I don't know if this is a casue or a symptom of the underlying problem but I wanted to put it out there.

I've also heard rumors that oiled air filters can dirty the MAP sensor, so I'm going to check that out this afternoon. But, I didn't notice anything weird from the MAP when driving this morning.

Thanks again for the suggestions,

Derek.
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Old 04-18-2005, 02:56 PM   #18
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If the fuel trims are off, how are the oxygen sensors in the exhaust system? Specifically, the front? How has your gas mileage been?

Might be your front sensor is going/gone and giving you all these issues.

AJ
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Old 04-19-2005, 12:12 AM   #19
b5o5m5b
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Yeah AJ, I'm starting to think the same thing, but mileage hasn't changed much that I've noticed. I still get around +320mi per tank.

I think I'm just going to break down and drop the $150 for a new sensor and see if that fixes it. The trims were just acting so eratic that I'm pretty convinced that this must be the problem.

Has anyone seen any good documentation on how the ECU controls the trim? I found a good how to that someone wrote for an Audi TT, but I havn't seen anything for Subaru, or the RS in particular. I'm intersted in reading more about the numbers that I'm seeing and how the ECU calculates them.

Thanks again to all those with suggestions.

D.
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Old 04-19-2005, 01:12 AM   #20
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Sounds IDENTICAL to what I just went through. I was determined to solve it myself and ended up replacing all plugs, wires, coilpack, etc... It turned out to be a bad 02 sensor. The same sensor was replaced under the 00 rs recall 1 year 2 months earlier.
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Old 04-19-2005, 02:12 AM   #21
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Quote:
Originally Posted by b5o5m5b
Yeah... that was the obvious and that's why I already checked it before posting to the list. The plugs and wires are all seated well.
Checked what, exactly?

Did you re-install the original plug wires and try it?

Did you gap the spark plugs correctly?

Did you let a plug slide down to the cylinder head and trash the gap?
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Old 04-25-2005, 01:31 AM   #22
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Yeah, that's about right.

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I'm having a similar problem ... car misfires when it gets hot, mostly after long pulls uphill. Except I don't have a CEL, and the car failed the emissions inspection with high NOx readings.

Shame on those of you who have been suggesting everything under the sun without reading the original post carefully.

b5o5m5b, did replacing the front O2 help?
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