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Not running properly, misfiring


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24 replies to this topic

#1 Speedwagon

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Posted 07 October 2012 - 02:22 PM

'98 Legacy GT. Swapped the EJ25 block with an EJ20G block (HG blew again in the EJ25). Still having misfiring issues, seemingly electrical in nature. When the engine heat soaks(has been run for awhile, then turned off and sits for a bit when it is hot out), upon restart I will get a misfire. This can be cleared by revving it out.

However, it doesn't always run properly below 4k rpm. Above 4k, and it seems to run great. But it seems to get the occasional misfire below 4k.

Any thoughts on just what could be causing this? Codes indicate misfires on multiple cylinders, so it has to be something common to all.

#2 Rooster2

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Posted 07 October 2012 - 05:21 PM

Coil pack maybe gone bad??

#3 Speedwagon

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Posted 07 October 2012 - 08:12 PM

Coil pack maybe gone bad??


If that's it, it'll be the second time on this car. Not unheard of though, since it is an aftermarket piece. I'll have to do some DMM readings on it.

#4 1 Lucky Texan

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Posted 07 October 2012 - 11:59 PM

crank angle sensor?

#5 Fairtax4me

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Posted 08 October 2012 - 12:13 AM

Any signs of coolant loss?
Checked plugs for oil or fuel fouling? Wet? Green?

#6 Speedwagon

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Posted 08 October 2012 - 10:58 AM

Any signs of coolant loss?
Checked plugs for oil or fuel fouling? Wet? Green?


Technically, yes, but because I had a hole in my radiator. Which is now fixed. So coolant should be stable now.

#7 Speedwagon

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Posted 08 October 2012 - 11:00 AM

crank angle sensor?


Aftermarket, replaced it when I changed the oil pump and couldn't get the old one out(less than a year ago).

#8 1 Lucky Texan

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Posted 08 October 2012 - 01:59 PM

hmmm, I know it's tight, but, would it be possible to use a heat gun and/or some 'freeze mist to test the CAS? If the engine is idling well, and heating the CAS made it stumble, OR, if the car was showing the problem and idling poorly and some freeze spray direct at the CAS settle the miss down, might be diagnostic for the sensor.

also, I wonder if the alternator/charging circuit could be a problem? ripple or low voltage?

#9 Speedwagon

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Posted 14 October 2012 - 01:34 PM

Update: I cleaned the MAF Friday, to see if that would change anything, as I had a long drive to do yesterday. Wasn't hot out, so I can't say anything about that.

Startup yesterday was fine. But after awhile down the highway, I noticed the issues again below 4k rpm. What it feels like to me, is almost like a fuel starvation problem. A few quick jerks while holding steady rpm, around the 3-3.5k mark. If I get the engine above ~4k, it cleans up and feels like it gets a little more power. Also, radiator is holding steady, and no evidence of anymore coolant loss. I'll probably go over to the shop later today, and pull the codes again to see what it has, and reset.

I'm not familiar with the CAS acronym. What is that?

#10 1 Lucky Texan

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Posted 14 October 2012 - 11:41 PM

Update: I cleaned the MAF Friday, to see if that would change anything, as I had a long drive to do yesterday. Wasn't hot out, so I can't say anything about that.

Startup yesterday was fine. But after awhile down the highway, I noticed the issues again below 4k rpm. What it feels like to me, is almost like a fuel starvation problem. A few quick jerks while holding steady rpm, around the 3-3.5k mark. If I get the engine above ~4k, it cleans up and feels like it gets a little more power. Also, radiator is holding steady, and no evidence of anymore coolant loss. I'll probably go over to the shop later today, and pull the codes again to see what it has, and reset.

I'm not familiar with the CAS acronym. What is that?


crank angle sensor. reads the little tabs behind the crank sprocket for the ECU to determine plug firing.

#11 Speedwagon

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Posted 15 October 2012 - 01:07 AM

Ok. Maybe I'll try and snag one from the boneyard, and swap it out. Shouldn't cost more than $10, if that.

#12 1 Lucky Texan

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Posted 15 October 2012 - 07:43 AM

Ok. Maybe I'll try and snag one from the boneyard, and swap it out. Shouldn't cost more than $10, if that.



longshot but cheap enough to try I guess.

good luck

#13 davebugs

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Posted 15 October 2012 - 08:13 AM

Ok. Maybe I'll try and snag one from the boneyard, and swap it out. Shouldn't cost more than $10, if that.


Take you favorite penetrant. Those puppies get gaulded in there. Often ruined when removed.

Depending on whar you run across grab the while oil pump piece that has this sensor in it. I have trouble getting these sensors out from the engine or from the bottom with the piece the oil pump is in removed from the engine.

Which also means it's easy to disable the car for a while when you have to dig all the pieces out. Hose pliers are helpful. But it is hard to get a good grip. And often the metal will turn on the plastic.

#14 Speedwagon

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Posted 15 October 2012 - 12:19 PM

Take you favorite penetrant. Those puppies get gaulded in there. Often ruined when removed.

Depending on whar you run across grab the while oil pump piece that has this sensor in it. I have trouble getting these sensors out from the engine or from the bottom with the piece the oil pump is in removed from the engine.

Which also means it's easy to disable the car for a while when you have to dig all the pieces out. Hose pliers are helpful. But it is hard to get a good grip. And often the metal will turn on the plastic.


Yeah, my old one certainly was. I'm hoping that the junkyard cars will be fairly easy, since there isn't much corrosion out here.

I can't say for sure, but it almost felt like the engine was pulling timing around the 3-3.5k mark as I drove home last night. Just a bunch of quick stumbles, that kept happening as I kept it in the rpm range.

#15 Speedwagon

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Posted 15 October 2012 - 08:22 PM

Pulled the codes today.

P0301 Cylinder 1 misfire
P0302 Cylinder 2 misfire
P0304 Cylinder 4 misfire
P0403 EGR (which I knew about, the EJ20G block doesn't have the EGR port)
P0463 Fuel level sensor A circuit high input

Freeze frame data said 3500rpm, 185F, 0mph

The most interesting thing, is that I erased the codes. The next few startups, it was misfiring like crazy. As if I reset the computer, and it had adapted to something that was malfunctioning before. It hasn't done the blatant misfire on startup in a few weeks, and didn't do it earlier today, until I erased codes.

#16 unibrook

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Posted 23 October 2012 - 01:18 PM

When was front 02 sensor last replaced?
When old and tired, this sensor will cause misfire stumbling.
And by old, I mean my 2001 Forester seems to want a new one every 40k miles.

#17 Fairtax4me

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Posted 23 October 2012 - 06:34 PM

I had a misfire that baffled me for days. Swapped everything I could think of. It was fine when cold but had problems once warm. Above about 3.5k - 4k rpm it was fine. Below that it would misfire randomly and I had codes for all 4 cylinders at one point or another. Timing belt was off a tooth. :-p

Front O2 sensor can cause problems once the engine is warm. Those can usually be checked by unplugging the sensor to see how well the engine runs without it. Problem gone? probably means you need a new front O2 sensor.

Knock sensor is another favorite to cause misfire problems. It's worth inspecting for corrosion on the base and cracks in the housing even if you don't replace it. New knock sensors are only about $20 on Ebay.

#18 davebugs

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Posted 23 October 2012 - 06:52 PM

I had a misfire that baffled me for days. Swapped everything I could think of. It was fine when cold but had problems once warm. Above about 3.5k - 4k rpm it was fine. Below that it would misfire randomly and I had codes for all 4 cylinders at one point or another. Timing belt was off a tooth. :-p

Front O2 sensor can cause problems once the engine is warm. Those can usually be checked by unplugging the sensor to see how well the engine runs without it. Problem gone? probably means you need a new front O2 sensor.

Knock sensor is another favorite to cause misfire problems. It's worth inspecting for corrosion on the base and cracks in the housing even if you don't replace it. New knock sensors are only about $20 on Ebay.


I have never seen a knock sensor cause a misfire. The car to run like crap and often no CEL - yes. But they are often bad, so no harm in checking it.

And when I've seen the belt off a tooth what caused the folks to contact me was often some kind of weird occasional cam and crank sensor type errors. Since the ECU can't tell which one is off. Occasionally it would get an error and the CEL would come on. I forget if it was advanced or retarded a tooth, that may have an impact on the code reported.

#19 Speedwagon

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Posted 08 December 2012 - 03:48 PM

Update:

Checked the timing belt, did a tooth count and it came out correctly.

Checked the coil: secondary is spot on, primary (on a really crappy DMM) was 1.2 (spec is 0.73)

Pulled the codes, got P0301, 302, 303, 304, 403. All cylinder misfires, and the 403 is the EGR(which has not been hooked up, since the EJ20G block doesn't have a port for it).

Reset the computer, and I know have a confirmed new symptom: everytime I reset the codes, it runs like crap until it learns something. Not throwing any codes yet, but it's misfiring(?) consistently somewhere at the moment.

I also reangled the knock senser, since the FSM said it should be at a 45 angle.

I replaced the crank sensor a few weeks ago, with a junkyard one(I had an aftermarket, now it has an OEM).

Pulled all the spark plugs, and they all looked the same. No indications of unburnt fuel.

Had someone else listen to it just now, and he described it as more of a flutter than a misfire.

Edited by Speedwagon, 08 December 2012 - 04:02 PM.


#20 Cougar

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Posted 09 December 2012 - 09:21 AM

As was already suggested you might try disconnecting the front O2 sensor to see if that changes things.

#21 Speedwagon

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Posted 09 December 2012 - 12:10 PM

As was already suggested you might try disconnecting the front O2 sensor to see if that changes things.


Ok... but the O2 sensors don't explain a cold startup issue from what I know, like was experienced when I reset the computer codes. To my knowledge, they are only active when the vehicle is fully warmed up.

#22 Speedwagon

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Posted 15 December 2012 - 03:17 PM

Ok... but the O2 sensors don't explain a cold startup issue from what I know, like was experienced when I reset the computer codes. To my knowledge, they are only active when the vehicle is fully warmed up.


I suppose there could be two issues happening at the same time though. Some sensor could be out of wack, causing the startup misfire/rough running, and the O2 sensor could be causing the 3-4k rpm stumbles.

I just swapped out the cam sensor with a junkyard OEM sensor. We'll see how that goes. I'll probably order a new O2 sensor shortly(it certainly wouldn't hurt to put a new one in anyways).

#23 naru

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Posted 16 December 2012 - 12:09 AM

'98 Legacy GT. Swapped the EJ25 block with an EJ20G block (HG blew again in the EJ25). Still having misfiring issues, seemingly electrical in nature. When the engine heat soaks(has been run for awhile, then turned off and sits for a bit when it is hot out), upon restart I will get a misfire. This can be cleared by revving it out.

However, it doesn't always run properly below 4k rpm. Above 4k, and it seems to run great. But it seems to get the occasional misfire below 4k.

Any thoughts on just what could be causing this? Codes indicate misfires on multiple cylinders, so it has to be something common to all.


The fact that it clears up w/a good rev very strongly suggests fouled plugs.Fuel or coolant.
What does the O2 sensor say w/it is running poorly?

Reused the same injectors?

I would put a pressure gauge on it to see if an injector or two is leaking while it sits.Running symptoms sound like they fit.
Found a leaky one last week on mine.

Don`t get too hung up on the "it has to be something common to all" thing.

#24 Speedwagon

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Posted 17 December 2012 - 10:26 AM

As I said, it was only the block that was swapped. Intake manifold and everything is the same, so yes the stock injectors.

After swapping out the cam sensor, the problems between 3-4k rpm seem to have gone away. It might be too early to make that call, but with a drive between Denver and Boulder yesterday, I wasn't having any problems.

Coolant level is steady. I had, previously, thought there might be a problem maintaining fuel pressure. Though I can't say I've given that much thought recently. I'll have to wait and see how the cam sensor pans out. If the problem returns, I'll check the fuel pressure.

#25 Speedwagon

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Posted 26 January 2013 - 10:17 PM

Got a good price on a new coil pack and knock sensor from the junkyard today. So far, it seems to be running better. But it might, again, be too early to tell. The old knock sensor was a bit rusty. Hopefully I won't be chasing this gremlin anymore.




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