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Old 02-17-2020, 02:34 AM   #1
jugomutt
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Default EJ207 high rpm misfire

Right to the point:

The car is a 2000 Subaru Impreza WRX STI. JDM Bugeye with original EJ207. Drivetrain is completely stock except for a catback exhaust (stock ECU, air filter, everything)

The issue is that is has a slight intermittent misfire at higher RPM (5k+). Seems to do it at 5100rpm and a couple other spots between that and 8000rpm. Its noticeable regardless of how much throttle is being applied. Along with the misfires, the CEL will flash. It gives the code "P0430 Camshaft Position Sensor 'A' Circuit Signal Fault Bank 1 Or Single Sensor" which seems unusual. This issue happens only when the engine is at full operating temp. No misfire or CEL before that, regardless of RPM.

So far I have:
- Swapped bank 1 and bank 2 cam sensors- no change
- Replaced bank 1 cam sensor with a working used one- no change
- Cleaned oil/residue off both cam sensor contacts and wires. Same for AVCS.
- Cleaned MAF
- Checked spark plugs- they look fairly good

Any idea what it could be?

I'd like to have a better idea of the issue before I start replacing parts.
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Last edited by jugomutt; 02-18-2020 at 04:40 AM.
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Old 02-19-2020, 08:42 AM   #2
dr20t
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What spark plugs are you running? And what boost level? Fuel?
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Old 02-20-2020, 12:35 AM   #3
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What did you gap your spark plugs to?
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Old 02-22-2020, 02:56 PM   #4
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Quote:
Originally Posted by jugomutt View Post
Right to the point:

The car is a 2000 Subaru Impreza WRX STI. JDM Bugeye with original EJ207. Drivetrain is completely stock except for a catback exhaust (stock ECU, air filter, everything)

The issue is that is has a slight intermittent misfire at higher RPM (5k+). Seems to do it at 5100rpm and a couple other spots between that and 8000rpm. Its noticeable regardless of how much throttle is being applied. Along with the misfires, the CEL will flash. It gives the code "P0430 Camshaft Position Sensor 'A' Circuit Signal Fault Bank 1 Or Single Sensor" which seems unusual. This issue happens only when the engine is at full operating temp. No misfire or CEL before that, regardless of RPM.

So far I have:
- Swapped bank 1 and bank 2 cam sensors- no change
- Replaced bank 1 cam sensor with a working used one- no change
- Cleaned oil/residue off both cam sensor contacts and wires. Same for AVCS.
- Cleaned MAF
- Checked spark plugs- they look fairly good

Any idea what it could be?

I'd like to have a better idea of the issue before I start replacing parts.
i would bet coils
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Old 02-25-2020, 08:03 PM   #5
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The cars running NGK BKR6 or BKR7, dont remember off the top of my head. The spark plugs were installed before I bought the car so I'm not sure of the gap, I haven't checked. I'm assuming they've got the standard gap on them.

It could be the coils but then why the flashing cam sensor code?

Unless the misfire and cam sensor code are 2 separate issues but coincidentally happen at the same time??
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Old 02-25-2020, 08:05 PM   #6
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Quote:
Originally Posted by dr20t View Post
What spark plugs are you running? And what boost level? Fuel?
Should be the stock boost level, can't provide a measurement because I don't have a gauge. Normally I use 94 octane, tried Shell V-power 91 once just to test but it made no difference.
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Old 02-26-2020, 02:27 AM   #7
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Check plugs, plug gap and coils in that order

I have seen bad coils / misfires cause cam sensor code to be spat out before.

Mick
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Old 03-05-2020, 07:30 PM   #8
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Just checked the plugs, all gaps were 0.030". Seemed to be in good shape, just a bit dirty. I replaced them anyway. Coilpacks and connectors all seem to be in good shape as well. Didn't see any tears, discoloration, or obvious damage.

Issue still persists, any other ideas?
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Old 03-05-2020, 10:06 PM   #9
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Default EJ207 high rpm misfire

Install new OEM coilpacks, they are old at this point. When my ej207 coilpacks got weak they were causing issues like you describe.
A bad alternator can also cause similar issues
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Old 03-05-2020, 11:02 PM   #10
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Quote:
Originally Posted by jugomutt View Post
Just checked the plugs, all gaps were 0.030". Seemed to be in good shape, just a bit dirty. I replaced them anyway. Coilpacks and connectors all seem to be in good shape as well. Didn't see any tears, discoloration, or obvious damage.

Issue still persists, any other ideas?
0.030 is too wide. Gap them to 0.024 and if you are still experiencing misfire issues. It's your coils.
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Old 03-06-2020, 08:51 AM   #11
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Quote:
Originally Posted by Fierysun View Post
0.030 is too wide. Gap them to 0.024 and if you are still experiencing misfire issues. It's your coils.


0.030 will be fine for his stock boost levels. I would suggest itís coils based on the above. Or as drodman said alternator / charging issue.

The coils may ďlookĒ ok but unless youíre measuring output / breakup, looks can be deceiving.

Mick
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Old 03-08-2020, 04:31 PM   #12
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Quote:
Originally Posted by dr20t View Post
0.030 will be fine for his stock boost levels. I would suggest it’s coils based on the above. Or as drodman said alternator / charging issue.

The coils may “look” ok but unless you’re measuring output / breakup, looks can be deceiving.

Mick

That's a false statement if you are trying to track down a misfire issue.

Definitely gap them down to .024 and see how it's behaving. There is no power gains at .030.

Last edited by Fierysun; 03-08-2020 at 04:37 PM.
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Old 03-08-2020, 07:55 PM   #13
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I was about to re-gap them but the packaging on the BKR7EIX stated not to gap them because the electrode was too fine. 0.030" is the standard gap on those.

The misfiring/CEL progressively gets worse as the engine gets closer to operating temp. When cold(ish) its non-existent. By the time it's been driven about 30 minutes it's very obvious.

It also depends on engine load. 1st/2nd gear the CEL flashes but pulls normally. 3rd gear it's worse, 4th it's clearly stuttering/hesitating above 5000rpm.
Driving downhill is not too bad, uphill is definitely harder.
Ex) if the engine is hot, I'm in 4th gear and going WOT uphill, that's the ultimate misfiring trifecta lol.

Hoping this info might help isolate the cause of the issue, before I replace the coilpacks.

Last edited by jugomutt; 03-08-2020 at 08:02 PM.
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Old 03-08-2020, 08:53 PM   #14
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You can definitely gap them down. You just can't smash the ground into the electrode.
I compress them in a bench vice and until a feeler gauge one size smaller than desired gap starts to drag.
Those plugs came at 0.031 and I had to drop to 0.026 to allow +16lbs of boost.
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Old 03-09-2020, 04:10 AM   #15
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Quote:
Originally Posted by Fierysun View Post
That's a false statement if you are trying to track down a misfire issue.

Definitely gap them down to .024 and see how it's behaving. There is no power gains at .030.


Gapping down to 0.024 will reduce the load on the coils - so it will mask any coil issues heís trying to detect.

If it makes the problem worse then it can only be related to the spark plugs themselves. Which wouldnít be causing an issue if gapped at 0.030 in any event, thus introducing a further, unnecessary variable into the mix.

OP - what youíre experiencing sounds like break up under load. Sounds more and more like coil / cas related unfortunately.

If your gap was way out there say at 0.040Ē and this was happening, I could understand potential spark blow out at moderate load / boost. But the plugs being at the stock gap at 0.030 indicates something else is wrong in the system.

Do you have proper chassis and engine earth wiring - have you checked the negative terminal to chassis wire and made sure itís sound? Coils rely on the delta and a bad earth can wreak havoc for coils.

Mick
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Old 03-09-2020, 01:41 PM   #16
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Quote:
Originally Posted by dr20t View Post
Gapping down to 0.024 will reduce the load on the coils - so it will mask any coil issues heís trying to detect.

If it makes the problem worse then it can only be related to the spark plugs themselves. Which wouldnít be causing an issue if gapped at 0.030 in any event, thus introducing a further, unnecessary variable into the mix.

OP - what youíre experiencing sounds like break up under load. Sounds more and more like coil / cas related unfortunately.

If your gap was way out there say at 0.040Ē and this was happening, I could understand potential spark blow out at moderate load / boost. But the plugs being at the stock gap at 0.030 indicates something else is wrong in the system.

Do you have proper chassis and engine earth wiring - have you checked the negative terminal to chassis wire and made sure itís sound? Coils rely on the delta and a bad earth can wreak havoc for coils.

Mick
Yes, I removed the grounding wire, cleaned off all the crud that was on/around it and reinstalled it. No noticeable difference.

Seems like coilpacks are the place to start, hopefully replacing them will solve the issue. I'll report back once I have the new ones out in!
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Old 03-09-2020, 05:22 PM   #17
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Quote:
Originally Posted by jugomutt View Post
Yes, I removed the grounding wire, cleaned off all the crud that was on/around it and reinstalled it. No noticeable difference.

Seems like coilpacks are the place to start, hopefully replacing them will solve the issue. I'll report back once I have the new ones out in!
you might want to change all them, I had 2 that were on its way out and the car ran okay at idle but you chouldnt step on the gas at all.
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Old 03-09-2020, 09:19 PM   #18
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Quote:
Originally Posted by dr20t View Post
Gapping down to 0.024 will reduce the load on the coils - so it will mask any coil issues he’s trying to detect.

If it makes the problem worse then it can only be related to the spark plugs themselves. Which wouldn’t be causing an issue if gapped at 0.030 in any event, thus introducing a further, unnecessary variable into the mix.

OP - what you’re experiencing sounds like break up under load. Sounds more and more like coil / cas related unfortunately.

If your gap was way out there say at 0.040” and this was happening, I could understand potential spark blow out at moderate load / boost. But the plugs being at the stock gap at 0.030 indicates something else is wrong in the system.

Do you have proper chassis and engine earth wiring - have you checked the negative terminal to chassis wire and made sure it’s sound? Coils rely on the delta and a bad earth can wreak havoc for coils.

Mick
If the coils are bad, they will also be bad at .024. The .030 is too wide even for stock. The whole point is to confirm the coils are bad even with an ideal gap.

Last edited by Fierysun; 03-09-2020 at 09:44 PM.
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Old 03-09-2020, 11:33 PM   #19
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Quote:
Originally Posted by Fierysun View Post
If the coils are bad, they will also be bad at .024. The .030 is too wide even for stock. The whole point is to confirm the coils are bad even with an ideal gap.


Sorry but I disagree. I know what youíre getting at but itís flawed logic. A smaller gap could mask the coil issue as the load reduces (like I said above).

Letís say he gapped them down to 0.024 and it runs ok under load. Idle and off boost would be **** and I would bet mileage would suffer too. But the main problem is the coils arenít operating at their standard load and thus itís masking the problem. There are other issues with running a smaller gap too which is beyond the scope of this thread.

Also re 0.030 being too large a gap - I can absolutely confirm that Iíve run 28.5psi on a 0.031 gap in an ej207 on e85 with no problems - this was on my previous v10 Grb ej207 but the same concept applies.

Bottom line - 0.030 is standard gap (and factory manual for ej207 shows standard gap as 0.7-0.8mm (0.028 to 0.0315) - so not too large a gap at all

Mick
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Old 03-16-2020, 11:05 PM   #20
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Originally Posted by dr20t View Post
Sorry but I disagree. I know what you’re getting at but it’s flawed logic. A smaller gap could mask the coil issue as the load reduces (like I said above).

Let’s say he gapped them down to 0.024 and it runs ok under load. Idle and off boost would be **** and I would bet mileage would suffer too. But the main problem is the coils aren’t operating at their standard load and thus it’s masking the problem. There are other issues with running a smaller gap too which is beyond the scope of this thread.

Also re 0.030 being too large a gap - I can absolutely confirm that I’ve run 28.5psi on a 0.031 gap in an ej207 on e85 with no problems - this was on my previous v10 Grb ej207 but the same concept applies.

Bottom line - 0.030 is standard gap (and factory manual for ej207 shows standard gap as 0.7-0.8mm (0.028 to 0.0315) - so not too large a gap at all

Mick
I completely disagree, but it's no skin (money out of my pocket) off my motor.

Gap it down to .024 and go from there.
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Old 03-28-2020, 04:06 PM   #21
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Update: new coilpacks are in- they made zero difference, the issue is still present. I was hoping they would at least reduce the issue but the misfiring/CEL flashing is behaving identical to the way it was before.

I'm thinking next I will:
- Gap down the plugs
- Replace the pigtail connector/wires for cam sensor. What are the odds of this being the issue?
- Any other ideas?
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Old 03-28-2020, 05:56 PM   #22
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Quote:
Originally Posted by jugomutt View Post
Update: new coilpacks are in- they made zero difference, the issue is still present. I was hoping they would at least reduce the issue but the misfiring/CEL flashing is behaving identical to the way it was before.

I'm thinking next I will:
- Gap down the plugs
- Replace the pigtail connector/wires for cam sensor. What are the odds of this being the issue?
- Any other ideas?
I hope it's not something as simple as reducing the gap on the plugs
Would suck spending the $$ on the coilpaks & all
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Old 03-30-2020, 09:35 PM   #23
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I really donít want to sound like a broken record - but if itís a pretty stock setup then the oem plug gap should be fine and not causing any issues.

Iím sorry to hear the coils didnít fix it, but the problem must be related to something other than plug gap (unless thereís something youíre not telling us about your setup which j donít believe is the case)

I know you said youíve checked your earths - can you check the engine to chassis earth connection and fix that? Maybe even run a strap from your head to the chassis to be safe (as the coils ground out on the rocker covers)

Plug gap reduction is cheap to do I agree - so worth a try to eliminate the problem temporarily. However this will not be addressing the root cause within the system.

Mick
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Old 03-31-2020, 05:02 PM   #24
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I really don’t want to sound like a broken record - but if it’s a pretty stock setup then the oem plug gap should be fine and not causing any issues.

I’m sorry to hear the coils didn’t fix it, but the problem must be related to something other than plug gap (unless there’s something you’re not telling us about your setup which j don’t believe is the case)

I know you said you’ve checked your earths - can you check the engine to chassis earth connection and fix that? Maybe even run a strap from your head to the chassis to be safe (as the coils ground out on the rocker covers)

Plug gap reduction is cheap to do I agree - so worth a try to eliminate the problem temporarily. However this will not be addressing the root cause within the system.

Mick
Seriously, your advise cost him money he didn't need to spend.

Always start troubleshooting with the simplest solution and then go from there. You should always systematically rule out things one by one without buying new parts first. Only when you have ruled those out, then replace with new.

Also, a smaller gap doesn't necessarily mean temporary fix. Much like modified engines pushing a lot of boost using a smaller gap.

In addition, it may be worth trying new plugs with the smaller gap. I had "brand new" iridium spark plugs that was misfiring. Although we couldn't see the crack/issue, we knew it was there. After replacing with another set. The issue was resolved.

Last edited by Fierysun; 03-31-2020 at 05:16 PM.
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Old 04-05-2020, 09:25 PM   #25
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Quote:
Originally Posted by dr20t View Post
Check plugs, plug gap and coils in that order

I have seen bad coils / misfires cause cam sensor code to be spat out before.

Mick


This was my original advice. Something you should have checked before accusing people of costing others money unnecessarily.

Iíll stand by the comment that even if he gapped them down to 0.024 per your advice - the fundamental source issue would remain and potentially create further headaches for diagnosis in future (especially if he sold the car to someone unsuspecting at some point)
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