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Old 11-07-2001, 08:22 PM   #1
2yLiTe
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Join Date: Dec 1999
Location: Windsor, Ontario CANADA
Default P0301 Misfire Cyl 1 and CE light

Car:
MY98 2.5RS

Engine/Exhaust Mods:
Cat Cams
Ported and Polished intake manifold
Ported and Polished throttle body
UR Pulley
Headers
Straight-thru mid exhaust (first cat still in place)
Brullen exhaust
Apex-i SAFC
Rallispec intake

Issue:
CE light is on
Code P0301 (cyl 1 misfire)

Problem determination:

reset ecu (and reset CEL)
drove approx 400kms (250 miles) at highway speeds stopping at rest areas along the way (note speeds at rest area are between 0-30kms\hr. NO CE LIGHT

arrive at my destination (city; city driving) CE LIGHT comes on.

Resolution:
put dielectric grease on plug wire terminals - no result
check plugs (normal color) - n/a
replace ignition coil - no result
reset SAFC to zero values - no result

Status:
"Check Engine" light still on, with no additional codes except P0301

Future Plans:
remove SAFC (note SAFC was working fine for over a year) or perhaps verify connections.

Anyone have any theories? My mechanic (a Certified Subaru Mechanic) told me to replace wire #1 and #2 (since they are similar in length) to see if the wire is bad (if the misfire jumps to cyl 2)

My questions are... does a misfire have any relation to rich/lean conditions?

Could this be caused by a malfunctioning injector?

Any help would be greatly appreciated.

Since there is no Subaru dealer in my city, I'll be going to Toronto on Thanksgiving to see my mechanic.

Thanks all!!
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Old 11-08-2001, 01:02 AM   #2
tmat3
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I would replace the plug wires first. If that doesn't solve, then plugs. Misfires are usually caused by bad plugs or plug wires. It can be caused by ignition coil, but you replaced it.
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Old 11-08-2001, 02:09 AM   #3
HndaTch627
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just FYI misfire codes are rarely EVER caused by a spark plug. A wire maybe. You said you had cams?? when was the last time you checked valve clearance?? this is a nice way to end up with a misfire. does the car stumble?? Miss?? Hesitate?? I'd look for a bad injector if it does. It won't be a coil pakc unless dropping out on 2 cylinders.

Jeremy

If you need any help PM me.
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Old 11-08-2001, 02:41 AM   #4
2yLiTe
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I don't consider myself a mechanic (by any stretch of the imagination) which is why I left the install to a professional....

but when he installed the cams (August 2001), I distinctly remember him putting all new shims in (is this what you meant by valve clearance?)

Since the engine was pretty much rebuilt, it's easy to assume either scenario where the install caused or didn't cause the issue... but I'd like to try everything that I can before the engine has to be opened up again. (read $$$)

my logic forces me to ask the question... why only during city driving and not on the highway?

keep the info comin' guys... I'm almost at the end of my patience rope...
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Old 11-08-2001, 10:41 AM   #5
HndaTch627
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oh ia m sorry....didn't see you had a 98...i have never done those but i think they are like our passport setup's which are a PITA.

as far as the misfire during city driving it is because you are hitting that certain RPM where the misfire is occuring when city driving. On the highway you are at almost a set engine speed the whole time where as in the city you are not.

Kinda following me here??

I could be valve clearnce but unless you are hearing ticking 10 feet from the car i think you'll be allright on that. and yes i do understand that allmighty $$$ and how i have none of it . This is kinda weird. What RPM is the Misfire recorded at??

jeremy
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Old 11-08-2001, 12:11 PM   #6
SubyTechMaster
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Each time you set a CEL the ECU records Freeze Frame Data. This is to help determine the cause, lean, rich, spark, etc.

It could easily be valves. Valves don't wear loose, they grow tighter. Valves that wear-in and get tighter will make less noise. Under a load if you are running rich enough they may be staying cooler.

It could also be an injecter and the overlap of the valves under load can keep it from missing.

Most misfires are caused by ignition wires.
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Old 11-08-2001, 01:05 PM   #7
2yLiTe
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ok...

So should I heed the mechanic's advice and swap wires 1 and 2? just to see if the misfire is triggered on cyl 2?

I'm still running factory wires (er... never changed em), I was thinking of just buying stock wires again...(read: another wires debate) but if swapping 1 and 2 can yield me some insight, I would imagine that it's worth a try.

Any thoughts on this course of action?

and thanks again guys... this is great stuff!!
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Old 11-08-2001, 01:14 PM   #8
SubyTechMaster
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In the time it took to write this you could have swapped the wires and found out. It is a harmless and non-intrusive diagnostic.
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Old 11-08-2001, 01:29 PM   #9
2yLiTe
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C'mon SubyTechMaster, cut me some slack..I'm at the office

I'll try it later when I get home... I'm going to reset the CEL and the ECU before I do it...

I'll report back this afternoon... wish me luck ($$$) hoping its the wire.
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Old 11-08-2001, 02:39 PM   #10
SubyTechMaster
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I-Club on company time? tsk, tsk.

Hopefully the misfire is a dependable one and not intermittant. If it's a bad wire sometimes you can see it arcing in the dark, difficult to do if it only happens under load though.

Good luck.
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Old 11-08-2001, 08:56 PM   #11
munkis
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how many miles on your car....

I would go for the wires right away...especially if they are original...my friend had a misfire..IMPREZAmike.

took me two seconds to find a bad wire, since as soon as I touched it it starte arcing right to my finger...fun ...the dealer told him they they didnt know what was wrong and that would have to do valve job if the light came back on

Found the cylinder three wire had become loose, and the lead was spread causeing arcing...it got corroded and eventually resulted in a no spark condition

OEM Subaru wires seem not to last very long, he switched them to magnecores...and poof no more misfire...

Wires Wires...I would have swapped the wires days ago, but then again is the car running rough at all?...wires usually cause a rough idle at the very least...

Test dont Guess hehe.

Jay McDade
Auto Tech--Lincoln/Mercury/Jaguar
www.hometown.aol.com/impreza25rs2000
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Old 11-08-2001, 09:09 PM   #12
2yLiTe
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ok, it's 9PM here in the Great Lakes area....

I had to work late and didn't get a chance to do my "mechanic bit"

I'll wait till tomorrow... but...to answer a few questions...

Car has 79,000kms on it (you do the math)

Rough? yeah it does idle a bit rough, but I'm assuming it's because of the cams. I was told to expect a little chunky idle (kinda sounds like a little V8)

Visual inspection of the wire revealed nothing.. I will reset the ECU (and clear the CEL) then try swapping the #1 and #2 wires to see if the misfire jumps to cyl 2. I was thinking of getting new wires but as I mentioned before... the debates on the pros and cons of wires has somewhat scared me away from the idea of going aftermarket. I'll give it a try tomorrow...

maybe I'll just buy a #1 wire, then if it goes away, I'll get the other 3.
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Old 11-08-2001, 09:45 PM   #13
munkis
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ahhh I hate math!, sounds like alot...heheh you should change the wires regardless, I havent heard anyone haveing any problems with magnecore wires.

ok works out to be 48980 miles...usually wires can go till 60,000 miles...but with all your mods...i would change them anyway...

Jay McDade

Last edited by munkis; 11-08-2001 at 09:53 PM.
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Old 11-09-2001, 06:49 PM   #14
2yLiTe
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Ok, went to the dealer and bought a brand spankin' new #1 Spark plug wire...

dealer cleared the codes (a P0105 - low voltage Mass Air Flow Sensor code came up...but let's concentrate on the P0301 first)

put the new wire in... and it ran CEL free for about 15 miles... then WHAMMO!! CEL!!!

I haven't pulled the code yet... but let's recap...

P0301 triggered
changed coil, still there
reset SAFC, still there
changed #1 spark plug wire, still there
next?....

possibilities...
change spark plugs (just changed em in the spring)
injector
faulty wiring on the SAFC i.e. remove SAFC

Help!?!?!?!
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Old 11-10-2001, 11:05 AM   #15
PerformanceAutoSolutions
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check the cam shaft installation.if the cam shaft sproket is off a tooth it could cause a mis fire code.if you can go back to the dealer ask them to use the old select monitor and check mis-fire percentage.do a compression test and cylinder leak down test,if the mis-fire percentage is 100% it is a electrical problem.i have also seen a worn camshaft support give mis-fire codes.
dave
mspt
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Old 11-10-2001, 01:00 PM   #16
HndaTch627
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well you need to eliminate that mass air flow code first....you might be surprised how one code can easily trigger another.

Jeremy
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Old 11-10-2001, 03:27 PM   #17
CSM101
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Just had my car at the dealer for a CE light.

Full story:
CE light came on, stopped by dealer, pulled code and reset light. Code showed misfire cyl 2.
Next morning light comes on. Get to dealer a week later. Code pulled and light reset.
Code showed misfire cyl 2,3 and 4.
Drive home and install new NGK plugs.
All 4 champions had gaps in execess of 45thou, max is 43thou.
3 days later light comes on. Make appointment with dealer and drop car off.
Dealer calls, code shows misfire on 2 and 3 cyl.
Dealer claims plugs were not gaped right and 2 plugs were loose.

I know how to gap plugs and have done 100's without fail in my life, set them to 40thou myself, think dealer is full of ****.
Dealer pulled all 4 and set gap to 41 thou, claimed 2 of mine were gapped too tight.
2 loose? Maybe, I did not use a torque wrench, possible H4 engines vibration characteristics shake them out?
Its been 2 days and the light has not come back on. Keeping my fingers crossed.

Lesson learned, CE light is very sensitive to plug conditions. The whole time my car ran fine and had no real misfire's to speak of. And yes I have felt real misfire's, very noticable on a 4 banger.

P.S. I have 23000 mile's on my car. Dealer tryed to give me a bunch of **** about changing the plug's myself and the repair not being under warrenty. Backed down after I asked to speak with the SOA rep. No charge.
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Old 11-10-2001, 04:05 PM   #18
HndaTch627
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actually i would beg to differ with what hte dealer told you.. NGK plugs are factory pregapped to the spec. And a spark plug will not cause a CE light unless you have detonated the plug electrode away. I am sure the light will probably come back on. But my question is why did the dealer NOT put the plugs in??

Jeremy
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Old 11-10-2001, 05:57 PM   #19
SubyTechMaster
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Many Subarus come with Champion Plugs (US parts content) and they are notorius for causing mis-fire codes. The dealer would have replaced them with NGK for free under warrenty. When you start replacing parts yourself you assume the responsibility for your own work.
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Old 11-10-2001, 06:18 PM   #20
2yLiTe
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Ok...

Just to keep it on track...

Today, I verified all the SAFC connections.. everything is nice and secure.

The battery's been disconnected for about 3 hours, and I'm on my way out.. I'm going to try and monitor the conditions under which the light comes on (I've already determined that the light doesn't come on while cruising at highway speeds)

so as of right now... it's isolated to cyl#1 although I don't know why a P0105 (low voltage mass air flow sensor) was triggered.

I'll keep you updated.
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Old 11-11-2001, 01:13 PM   #21
veowsaku
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I have the same problem, check your valve guide to see if it moved out of place or not. If valve guide moved out, it will prevent the valve to close completely so misfire will occur.

Khem
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