GSLENK
10+ Year Contributor
- 1,416
- 51
- May 25, 2011
-
DC,
Maryland
I know, not another misfire thread... But all my searches pretty much bring up the usual suspects, or the 1g/2g swap which is already well documented by now. Also, the bench tests for the ignition parts I feel are not all guaranteed to confirm good parts.
I am on a little bit of a budget here. I am not looking to spend ~$500 on coils and/or power TR unless absolutely necessary to guarantee ZERO misfires. I did find the testing literature for both and they "passed" as of last year (but we know what that means).
Quick and dirty on the relevant mods (pushing ~60lb/min, but not much when the miss occurs):
Ignition:
Factory. NGK wires, NGK BR7ES plugs. OEM and original everything else.
Fuel:
AEM 320 E85 pump
-6an PTFE SS feed and return lines
Fuel lab regulator at 43psi
Fuel lab SS mesh filter 40 micron I think
FIC BM1250cc
OEM fuel rail
Run E85 mostly, 93oct at least once every 2 months.
Air/Timing:
ECMlink v3 Full on Speed density
Omni 4-bar/GM IAT
Run both LC1 WB AND NB OEM sensor
So lets get a list of all the possible causes of a misfire on a 1g/6-bolt.
I know for sure:
--Plugs
--Wires
--Power TR
--Coils
--Injectors
--Fuel delivery
--Boost/vac leak
Is there anything else? (please confirm OR DENY these) (has any of these been known to cause a misfire as described, particularly an INTERMITTENT/seemingly random one)?
--Compression?
--CAS?
--TPS?
--Leakdown test (HG failure)?
--ECU?
Here's my trouble shooting so far:
--Plugs (BR7ES): At .025 replaced because they are cheap. Did nothing. See attached pics if there are any clues on plug condition after a year of use. BPR6ES and/or high gap has seen blowout on my FP red at 33+psi so the current ones may foul, but they treat me well otherwise, and I replace them relatively frequently (at least yearly).
--Wires: One year old. Maybe 2 years. NGK blue wires. Did not see any arcing when I check on a recent night. I did not check that thoroughly, but they "seem" ok.
--Power TR: Replaced by a used one from classifieds. Both the old and "new to me" passed a bench test. Seller claimed his was flawless. His feedback was good so I no reason to think otherwise.
--Coils: Never touched them. I did bench test them but they checked out ok, and I believe bad ones can still test ok.
--Injectors: "New but installed" so technically very light use. Seller feedback, receipt, smell, and seal condition support his claim that they did not see any significant use, if any at all. They pass the stethoscope test. They all work. Pulling the electrical clip makes the engine really misfire for each one.
--TPS has .63v at closed throttle. And the throttle switch works. ISC is adjusted perfect too.
--CAS was removed, cleaned, installed backward, then reinstalled correctly when I did valve stem seals. Car ran beautifully for about 2 days, then back to normal. (hence me asking about the CAS).
--Mechanical timing was also verified at that time.
--Base timing was verified next (base ignition advance 5BTDC).
--Compression was checked 2 years ago and was excellent. (high and consistent). I have no reason to suspect otherwise to this day, but I have a tester.
--I have talked about swapping ECU's but no one has taken me up on the offer of a nice 6 pack to borrow their ECU for some driving time.
--Last season I really cracked down on boost leaks (no system is perfect, but I was pretty damn close). I have not touched any of those parts of the car to warrant another check. Besides, I run SD.
Nothing else has been physically replaced or tested.
Anything else I should do or redo?
Onto the symptoms:
I can hear a random miss every now and then (every couple of seconds) no matter the temperature of the car. Rough driving seems to help cause really bad misfires, especially if the car is warm/hot or specifically on a hot day. Rough as in jerking the clutch, low rpm (~1-2k) driving, really sharp corner steering, or tough bumps. Combinations appear to make it worse. Sometimes I need to rev to 3k to get the car to move under its own power, but this is really rare, and seems to only happen when it is really hot or really rough driving or both.
Hot outside, and in the bay. My engine temps seldom go over 210 if ever, and typically stay in the 186-196 range. Up to 203 on a hot day. Turning the AC on drops me to 193-196 any day even on cold/full blast. Keeping the engine at 196 does seem to help but that's all I can say.
Car is in a pretty good state of tune. Stacey did pretty well, the misfire was not really detectable while he was tuning. It began to really rear its head recently. (missing one ignition event out of 20 or so is not all that significant, especially at full throttle). Missing a few in close proximity brings the jerks/boost/power loss. The mis clear up above 4k easy, but I can feel the lacking power, even if the car feels smooth.
On a misfire event, the AFRatioEst will spike lean. On the really bad event it will rapidly cycle between target and max lean (20:1) about as quickly as the car sputters. Measured AFR may spike a little, but not as badly. Also when the car is "moody" AFRatioEst tends to be estimated way leaner than mapped, and way leaner than the actual afr. This is not typical when the car is running relatively smooth, the two flip flop etc. and are relatively close.
I have tried to use a timing light on each plug wire, I could not draw any solid conclusions it looked like the misfire might jump around, but idle was not steady enough throughout the misses to determine where it was coming from. When a big miss came up, the engine speed dropped so I could not tell if cylinders were dropping or it was an artifact of reduced rpm.
ANY OTHER INFO NEEDED?
I am really tempted to just buy all new OEM coils, TR and wires but that's quite a hit and if they don't make it work I will be mad and broke.
Also, I can get Coils and a Power TR on ebay NEW for really cheap. They do not appear to be OEM, but I have see the inside of a TR, it looks simple enough to warrant aftermarket. Coils are another story, windings must be good so I can understand that. Transistors and resistors are pretty hard to screw up these days (and are really cheap).
Any thoughts on knockoff Ignition components? They are REALLY tempting right now.
I am on a little bit of a budget here. I am not looking to spend ~$500 on coils and/or power TR unless absolutely necessary to guarantee ZERO misfires. I did find the testing literature for both and they "passed" as of last year (but we know what that means).
Quick and dirty on the relevant mods (pushing ~60lb/min, but not much when the miss occurs):
Ignition:
Factory. NGK wires, NGK BR7ES plugs. OEM and original everything else.
Fuel:
AEM 320 E85 pump
-6an PTFE SS feed and return lines
Fuel lab regulator at 43psi
Fuel lab SS mesh filter 40 micron I think
FIC BM1250cc
OEM fuel rail
Run E85 mostly, 93oct at least once every 2 months.
Air/Timing:
ECMlink v3 Full on Speed density
Omni 4-bar/GM IAT
Run both LC1 WB AND NB OEM sensor
So lets get a list of all the possible causes of a misfire on a 1g/6-bolt.
I know for sure:
--Plugs
--Wires
--Power TR
--Coils
--Injectors
--Fuel delivery
--Boost/vac leak
Is there anything else? (please confirm OR DENY these) (has any of these been known to cause a misfire as described, particularly an INTERMITTENT/seemingly random one)?
--Compression?
--CAS?
--TPS?
--Leakdown test (HG failure)?
--ECU?
Here's my trouble shooting so far:
--Plugs (BR7ES): At .025 replaced because they are cheap. Did nothing. See attached pics if there are any clues on plug condition after a year of use. BPR6ES and/or high gap has seen blowout on my FP red at 33+psi so the current ones may foul, but they treat me well otherwise, and I replace them relatively frequently (at least yearly).
--Wires: One year old. Maybe 2 years. NGK blue wires. Did not see any arcing when I check on a recent night. I did not check that thoroughly, but they "seem" ok.
--Power TR: Replaced by a used one from classifieds. Both the old and "new to me" passed a bench test. Seller claimed his was flawless. His feedback was good so I no reason to think otherwise.
--Coils: Never touched them. I did bench test them but they checked out ok, and I believe bad ones can still test ok.
--Injectors: "New but installed" so technically very light use. Seller feedback, receipt, smell, and seal condition support his claim that they did not see any significant use, if any at all. They pass the stethoscope test. They all work. Pulling the electrical clip makes the engine really misfire for each one.
--TPS has .63v at closed throttle. And the throttle switch works. ISC is adjusted perfect too.
--CAS was removed, cleaned, installed backward, then reinstalled correctly when I did valve stem seals. Car ran beautifully for about 2 days, then back to normal. (hence me asking about the CAS).
--Mechanical timing was also verified at that time.
--Base timing was verified next (base ignition advance 5BTDC).
--Compression was checked 2 years ago and was excellent. (high and consistent). I have no reason to suspect otherwise to this day, but I have a tester.
--I have talked about swapping ECU's but no one has taken me up on the offer of a nice 6 pack to borrow their ECU for some driving time.
--Last season I really cracked down on boost leaks (no system is perfect, but I was pretty damn close). I have not touched any of those parts of the car to warrant another check. Besides, I run SD.
Nothing else has been physically replaced or tested.
Anything else I should do or redo?
Onto the symptoms:
I can hear a random miss every now and then (every couple of seconds) no matter the temperature of the car. Rough driving seems to help cause really bad misfires, especially if the car is warm/hot or specifically on a hot day. Rough as in jerking the clutch, low rpm (~1-2k) driving, really sharp corner steering, or tough bumps. Combinations appear to make it worse. Sometimes I need to rev to 3k to get the car to move under its own power, but this is really rare, and seems to only happen when it is really hot or really rough driving or both.
Hot outside, and in the bay. My engine temps seldom go over 210 if ever, and typically stay in the 186-196 range. Up to 203 on a hot day. Turning the AC on drops me to 193-196 any day even on cold/full blast. Keeping the engine at 196 does seem to help but that's all I can say.
Car is in a pretty good state of tune. Stacey did pretty well, the misfire was not really detectable while he was tuning. It began to really rear its head recently. (missing one ignition event out of 20 or so is not all that significant, especially at full throttle). Missing a few in close proximity brings the jerks/boost/power loss. The mis clear up above 4k easy, but I can feel the lacking power, even if the car feels smooth.
On a misfire event, the AFRatioEst will spike lean. On the really bad event it will rapidly cycle between target and max lean (20:1) about as quickly as the car sputters. Measured AFR may spike a little, but not as badly. Also when the car is "moody" AFRatioEst tends to be estimated way leaner than mapped, and way leaner than the actual afr. This is not typical when the car is running relatively smooth, the two flip flop etc. and are relatively close.
I have tried to use a timing light on each plug wire, I could not draw any solid conclusions it looked like the misfire might jump around, but idle was not steady enough throughout the misses to determine where it was coming from. When a big miss came up, the engine speed dropped so I could not tell if cylinders were dropping or it was an artifact of reduced rpm.
ANY OTHER INFO NEEDED?
I am really tempted to just buy all new OEM coils, TR and wires but that's quite a hit and if they don't make it work I will be mad and broke.
Also, I can get Coils and a Power TR on ebay NEW for really cheap. They do not appear to be OEM, but I have see the inside of a TR, it looks simple enough to warrant aftermarket. Coils are another story, windings must be good so I can understand that. Transistors and resistors are pretty hard to screw up these days (and are really cheap).
Any thoughts on knockoff Ignition components? They are REALLY tempting right now.
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