Little help from the brain trust

[DOSS]

It has 4wd so lets get past the snide comments :greg: Anyhow here is the issue.. I am as well as my friends.. stumped

The Car
99 Subaru Outback with 150K

So the issue:
Multiple Cylinder misfire, Mostly cylinder 4 & 3 occasionally 2... I do not notice a rough idle or feel the miss when it happens. CEL codes only show up when driving at 3000 - 3200 RPM for 4-5 minutes and at no other speeds. Issue seems to be happening more frequently EEK

what has been done.
Recent engine rebuild
plugs, wires, coil pack
multiple tanks of fuel so I doubt it is a bad fuel issue
new fuel filter

Still to be done
I Plan today to check every ground and connection under the hood to see if it is a loose connection somewhere..
Otherwise what does the brain trust have to say...

 

[jevyguy]

Are the spark plugs the correct ones?
Crank or Cam Sensor?

What is the actual code?

 

[iamsparticus]

i would look at the crank sensor for sure, but a cam senor is possible too, did it run like this right after the rebuild?

 

[Zombie]

From what I've read, the crank sensor is likely your culprit.
I've had cam sensor failures in two of the subies I've owned (including my 99 outback) and it just killed the motor in both cases.
Now I have no scientific data to support this, but most of the sensor failures I've experienced on my subarus over the years (and I'm on number 3 and 4 currently) most of the sensor failures happen when the underhood temps are high. Even the knock sensor failures have happened only when the motor is warm. Does this match your observation?

I'd say if you issue happens more when the motor is warm, it's likely a sensor. If it happens when the motor is cold, it's a ground.

 

[DOSS]

Codes are P0302,3,4 lame generic cylinder misfire codes...

Engine did not run like this after the rebuild.. well it did as the engine actually runs great it just throws stupid codes.

Only happens when warm... I was thinking Crank sensor too.. hmmm - or some sensor.. just narrowing it down is the pain.. at least this is like voting right HEHE

Spark plugs are new NGK plugs and are the right ones.. hard time seeing plugs being the issue across a number of cylinders at a specific RPM...

 

[Zombie]

Start with the crank sensor... at that mileage it will need it soon if not being the root cause of your current issue.

 

[jevyguy]

Codes are P0302,3,4 lame generic cylinder misfire codes...

Spark plugs are new NGK plugs and are the right ones.. hard time seeing plugs being the issue across a number of cylinders at a specific RPM...

I agree, spark plugs are most likely not your problem. I have witnessed a V8 engine somehow eat all 8 at the same time. It had no spark on any of the cylinders, changes them out and Vroooom.

My dad recently had a misfire (only on 1 cylinder) in his car and the ceramic insulator was cracked ever so slightly, plugs were only 10k old.

 

[DOSS]

Well I am biting the bullet and going to put in new spark plugs.. 2+ hour job on this beast.. and I will put a new Crank position sensor in tonight when it shows up.. we will see what this does..

 

[zukking01]

Dont know if it helps or not buy I just put a new o ring on my toyota fuel injector on a toyota avalon with multi port. It was throwing a cylinder 5 misfire and it was all due to a small $2 or 4 o rings. It ran like a champ with the code for almost a year. Finally dug around to pass I/M.

Maybe it could be a fuel injector getting a minimal amount of leak being a fuel loss or a air breech to throw the code. Hope this might help.

 

[Zombie]

So... fixed?

 

[DOSS]

So... fixed?

So far the issue seems to have gone away.. Not sure if it was
A: Crank Position Sensor
B: Making every single connection under the hood a perfect connection
C: Throttle body cleaning
D: MAF cleaning
E: Spark Plugs

because I did all of them at once to see where it got me .. I am thinking CPS was the main culprit and I had been leaning that way until I got talked out of it but someone Thanks for everyone's help

 

[DOSS]

OK.. So just thought I would update this thread.. Finally found the issue after a lot of time and effort..

Things that have been checked/ replaced since posting here are
Crank position sensor, Cam Sensor, Engine control module, plugs, wires, checked valve clearance (yeah really), checked timing belt and alignment, MAFS, TPS,... in the end it was the computer .. akk..

thanks for the help yawl