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Cylinder 3 and 4 misfire on highway speeds


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17 replies to this topic

#1 wasabiboi

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Posted 06 May 2014 - 08:57 PM

Hello! Recently a CEL popped up blinking while on the highway. Pulling the code, it was a cylinder 3 and 4 misfire. 

 

This is a 1998 Subaru Legacy outback

 

Funny thing is, the blinking CEL only pops up when RPMs are above 3k or at 70+mph . Even so, there is no audible noise or power loss when the light comes on.  

 

If I drive local and stay off the highway, the CEL came on ONCE and it came on when I was holding a high RPM. No funny engine noises when the light blinks though. 

 

Ive replaced the Plugs with NGK Plats. and Wires to NGKs. Replaced coil pack as well. Switched around injectors and still have a 3 and 4 misfire.

 

Reading up on the exhaust dollar trick it seems that I do have suction though.

 

Not sure what to do or anything else I can try before bringing it in. Any suggestions would be greatly appreciated! 

 

Thank you!

 

Edit: The car functions fine until I reach (higher) highway speeds or extremely high rpm and it throws a blinking CEL.

 

Then it goes solid if I bring the RPMs back down. Accelerate back up to 3.5+k rpm in 5th gear and it starts blinking and goes solid and it'll stay solid if I'm driving local roads. No misfire noise, no shrudder, no loss of power.


Edited by wasabiboi, 07 May 2014 - 05:09 PM.


#2 Fairtax4me

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Posted 06 May 2014 - 09:37 PM

Generally spark or compression related misfires occur at low RPM.
When was the last time it got air and fuel filters?
Timing belt?

#3 nipper

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Posted 06 May 2014 - 10:10 PM

How many miles, auto or manual?


Edited by nipper, 06 May 2014 - 10:11 PM.


#4 wasabiboi

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Posted 06 May 2014 - 10:46 PM

Generally spark or compression related misfires occur at low RPM.
When was the last time it got air and fuel filters?
Timing belt?

 

I purchased the car about 3 months ago. 

 

Air filter looks clean, fuel filter not sure. 

 

Timing belt unsure, previous owner I believe did say something about it being done. The car is around 148,xxx.



#5 wasabiboi

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Posted 06 May 2014 - 10:47 PM

How many miles, auto or manual?

148,xxx.

 

Manual 



#6 nipper

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Posted 06 May 2014 - 10:55 PM

The coils are cyl 1-2 and 3-4. Two cylinders fire together. If it is possible (Don't remember if you can) swap the coils and see if the miss moves. 



#7 wasabiboi

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Posted 06 May 2014 - 11:22 PM

The coils are cyl 1-2 and 3-4. Two cylinders fire together. If it is possible (Don't remember if you can) swap the coils and see if the miss moves. 

I already swapped the entire coil pack with a new one. Same misfire issue. 



#8 cascadeclimbn

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Posted 07 May 2014 - 12:32 AM

Sounds to me like a fuel filter issue. Its a $20 part and easy to replace. I'd also look into replacing your timing belt.



#9 johnceggleston

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Posted 07 May 2014 - 06:21 AM

I already swapped the entire coil pack with a new one. Same misfire issue.

then it is likely the igniter,

mounted on the firewall.

it feeds the coil in the same front (1&2) vs rear (3&4) manner.



#10 britbiker

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Posted 07 May 2014 - 02:34 PM

On my '99 Outback the same symptoms were early warning of impending head gasket failure.



#11 wasabiboi

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Posted 07 May 2014 - 04:52 PM

On my '99 Outback the same symptoms were early warning of impending head gasket failure.

 

Headgasket was done less than 1k miles ago. (Although, the quality of job is questionable)



#12 wasabiboi

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Posted 07 May 2014 - 05:02 PM

then it is likely the igniter,

mounted on the firewall.

it feeds the coil in the same front (1&2) vs rear (3&4) manner.

What would be the reason the igniter going bad? The car functions fine until I reach (higher) highway speeds or extremely high rpm and it throws a blinking CEL.

 

Then it goes solid if I bring the RPMs back down. Accelerate back up to 3.5k rpm and it starts blinking and goes solid.  



#13 johnceggleston

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Posted 07 May 2014 - 05:28 PM

a blinking CEL indicates a condition that could harm the cats.

the most common cause of a blinking CEL is misfires.

 

if 2 cylinders are not firing at speed, you are dumping a lot of unburnt fuel into the exhaust.

 

the igniter is one possible cause of a ''front vs rear ''misfire,

just like the coli is.

but since you have replaced the coli,

next guess is the igniter.

 

but the MOST COMMON cause of misfires is plug wires, second is plugs.

but if you arer sure that is not your cause,

the igniter fits the symptoms.

 

have you move the plug wires from the rear cylinders to the front cylinders?

to see if the miss follows the wires?


Edited by johnceggleston, 07 May 2014 - 05:29 PM.


#14 wasabiboi

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Posted 07 May 2014 - 08:42 PM

a blinking CEL indicates a condition that could harm the cats.

the most common cause of a blinking CEL is misfires.

 

if 2 cylinders are not firing at speed, you are dumping a lot of unburnt fuel into the exhaust.

 

the igniter is one possible cause of a ''front vs rear ''misfire,

just like the coli is.

but since you have replaced the coli,

next guess is the igniter.

 

but the MOST COMMON cause of misfires is plug wires, second is plugs.

but if you arer sure that is not your cause,

the igniter fits the symptoms.

 

have you move the plug wires from the rear cylinders to the front cylinders?

to see if the miss follows the wires?

The coil pack has the male end that plugs into a female end of the wire. Not sure how to move them front to back.

 

But they're brand new plugs and wires I JUST put in two weeks ago when the issue came up.

 

I'll take a look at the igniter and fuel filters next.


Edited by wasabiboi, 07 May 2014 - 08:43 PM.


#15 1 Lucky Texan

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Posted 07 May 2014 - 10:33 PM

make certain the wires are snapped onto the plugs. read often of this being an issue. check the boots for oil, some soobs leak oil in the plug tubes and short  the high voltage, , perhaps try swapping injectors front to rear.



#16 wasabiboi

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Posted 08 May 2014 - 01:49 AM

make certain the wires are snapped onto the plugs. read often of this being an issue. check the boots for oil, some soobs leak oil in the plug tubes and short  the high voltage, , perhaps try swapping injectors front to rear.

 

I've checked the boots, they're clean.

 

Ive also switched around injectors. No change



#17 1 Lucky Texan

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Posted 08 May 2014 - 07:34 AM

well, may be time for compression and leakdown tests. maybe valves are burned, or just on the edge of being too tight and they float enough when warm at higher rpms to leak?



#18 MilesFox

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Posted 08 May 2014 - 08:46 AM

Next time it does this, pull over and see if there are any bubbles rising out of the overflow tank on the radiator. Also, observe where the fluid level is on the tank. If the level rises over time, coolant is being pushed out an air pocket is forming, which is indicative if compression gasses in the cooling.






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